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Article

Using the Singly Deprotonated Triethanolamine to Prepare Dinuclear Lanthanide(III) Complexes: Synthesis, Structural Characterization and Magnetic Studies †

1
Department of Chemistry, University of Patras, 265 04 Patras, Greece
2
Departament de Química Inorgànica i Orgànica, Secció Inorgànica, and Institue of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
3
Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, 153 10 Aghia Paraskevi Attikis, Greece
4
Institute of Chemical Engineering Sciences, Foundation for Research and Technology-Hellas (FORTH/ICE-HT), Platani, P.O. Box 1414, 265 04 Patras, Greece
*
Authors to whom correspondence should be addressed.
This article is dedicated to Dante Gatteschi, a pioneer in the interdisciplinary field of Molecular Magnetism and a great mentor, on the occasion of his 70th birthday.
Magnetochemistry 2017, 3(1), 5; https://doi.org/10.3390/magnetochemistry3010005
Submission received: 21 December 2016 / Revised: 13 January 2017 / Accepted: 16 January 2017 / Published: 26 January 2017
(This article belongs to the Special Issue Molecular Magnetism of Lanthanides Complexes and Networks)

Abstract

:
The 1:1 reactions between hydrated lanthanide(III) nitrates and triethanolamine (teaH3) in MeOH, in the absence of external bases, have provided access to the dinuclear complexes [Ln2(NO3)4(teaH2)2] (Ln = Pr, 1; Ln = Gd, 2; Ln = Tb, 3; Ln = Dy, 4; Ln = Ho, 5) containing the singly deprotonated form of the ligand. Use of excess of the ligand in the same solvent gives mononuclear complexes containing the neutral ligand and the representative compound [Pr(NO3)(teaH3)2](NO3)2 (6) was characterized. The structures of the isomorphous complexes 1∙2MeOH, 2∙2MeOH and 4∙2MeOH were solved by single-crystal X-ray crystallography; the other two dinuclear complexes are proposed to be isostructural with 1, 2 and 4 based on elemental analyses, IR spectra and powder XRD patterns. The IR spectra of 16 are discussed in terms of structural features of the complexes. The two LnIII atoms in centrosymmetric 1∙2MeOH, 2∙2MeOH and 4∙2MeOH are doubly bridged by the deprotonated oxygen atoms of the two η11122 teaH2 ligands. The teaH2 nitrogen atom and six terminal oxygen atoms (two from the neutral hydroxyl groups of teaH2 and four from two slightly anisobidentate chelating nitrato groups) complete 9-coordination at each 4f-metal center. The coordination geometries of the metal ions are spherical-relaxed capped cubic (1∙2MeOH), Johnson tricapped trigonal prismatic (2∙2MeOH) and spherical capped square antiprismatic (4·2MeOH). O–H∙∙∙O H bonds create chains parallel to the a axis. The cation of 6 has crystallographic two fold symmetry and the rotation axis passes through the PrIII atom, the nitrogen atom of the coordinated nitrato group and the non-coordinated oxygen atom of the nitrato ligand. The metal ion is bound to the two η1111 teaH3 ligands and to one bidentate chelating nitrato group. The 10-coordinate PrIII atom has a sphenocoronal coordination geometry. Several H bonds are responsible for the formation of a 3D architecture in the crystal structure of 6. Complexes 16 are new members of a small family of homometallic LnIII complexes containing various forms of triethanolamine as ligands. Dc magnetic susceptibility studies in the 2–300 K range reveal the presence of a weak to moderate intramolecular antiferromagnetic exchange interaction (J = −0.30(2) cm−1 based on the spin Hamiltonian H ^ = - J ( S ^ Gd 1 S ^ Gd 1 ) ) for 2 and probably weak antiferromagnetic exchange interactions within the molecules of 35. The antiferromagnetic GdIII∙∙∙GdIII interaction in 2 is discussed in terms of known magnetostructural correlations for complexes possessing the {Gd22-OR)2}4+ core. Ac magnetic susceptibility measurements in zero dc field for 35 do not show frequency dependent out-of-phase signals; this experimental fact is discussed and rationalized for complex 4 in terms of the magnetic anisotropy axis for each DyIII center and the oblate electron density of the metal ion.

Graphical Abstract

1. Introduction

Electrons residing in 4f orbitals give trivalent lanthanides (LnIII) interesting (and sometimes difficult to understand in detail) optical and magnetic properties that are currently exploited in modern technology. As far as magnetism is concerned, LnIII ions have been the key components of hard permanent magnets, such as the SmCo and FeNdB magnets, as well as the platform to investigate interesting physical phenomena, e.g., the spin-ice behavior in Dy2Ti2O7 [1]. LnIII complexes have also attracted intense interest since the first days of Molecular Magnetism, because of their high magnetic moments and large anisotropies [2]. However, it was after the discovery that magnetic anisotropy could lead to magnetic hysteresis at the molecular level in a class of compounds known as Single-Molecule Magnets (SMMs) [3,4] that an explosion in their study has occurred. In 2003, Ishikawa’s group reported SMM behavior in the double-decker phthalocyanine complexes (Bun 4N)[Ln(pc)2] (Ln = Tb, Dy) [5], which gave birth of the LnIII SMM era [6,7]. The magnetization dynamics of dinuclear and polynuclear LnIII SMMs mainly originate from single-ion behavior because it is difficult to create effective pathways for magnetic interactions between metal centers due to the nature of inner 4f electrons; in general, both the exchange and dipolar interactions between LnIII ions are weak [8]. This situation is different from the magnetic relaxation of transition-metal-based SMMs, in which both the spin and exchange interactions contribute simultaneously to the magnetization dynamics [3]. As an alternative candidate, LnIII centers that are usually weakly coupled in dinuclear and polynuclear complexes have shown advantages with respect to SMM studies because large magnetization reversal energy barriers can be achieved via single-ion anisotropy originating from strong spin-orbit coupling and crystal field effects [6,8,9].
Dinuclear complexes represent the simplest molecular entities which allow the study of magnetic interactions between LnIII spin carriers [10]. By studying such systems, researchers could expect to understand the nature and strength of LnIII··· LnIII exchange interactions, as well as possible alignment of spin vectors and anisotropy axes. These parameters can be affected by the molecular symmetry, the coordination geometry and/or the bridging ligands, which may act as superexchange pathways. More importantly, dinuclear LnIII SMMs are very important model systems to answer basic questions regarding single-ion relaxation vs. slow magnetic relaxation arising from the molecule as an entity. Thus, LnIII2 complexes are highly desirable [10,11,12,13,14,15,16,17,18,19,20]. Another interesting area to which dinuclear lanthanide(III) complexes (and also mononuclear ones) are relevant is quantum computation; LnIII ions are promising candidates for encoding quantum information [21,22]. For the realization of a quantum gate, asymmetric dinuclear molecules composed of two weakly coupled LnIII qubits are promising [21]. However, the synthesis of asymmetric molecular dimers is not straightforward, as nature tends to make them symmetric. From the synthetic inorganic chemistry viewpoint, the most logical simple route for the isolation of dinuclear 4f-metal ion complexes is the simultaneous employment of bidentate bridging anionic groups (e.g., η112 and/or η122 carboxylate groups) and chelating (most often bidentate or tridentate, e.g. bpy, phen, terpy, etc.) neutral capping organic ligands, which terminate oligomerization or polymerization by blocking two or three coordination sites per LnIII center [23]. Another method is the simultaneous employment of capping bidentate nitrato groups (nitrato ligands have little tendency for bridging in LnIII chemistry) and neutral or anionic organic ligands that can, in principle, bridge only two metal centers; in addition to the bridging functionality, the ligands should preferably possess “chelating” parts to satisfy the demand for high coordination numbers at the LnIII centers [24,25,26]. Thus, the choice of the primary organic ligands is crucial for the synthesis of LnIII2 complexes.
With all the above in mind and given the recently initiated interest of our groups in LnIII2 complexes with interesting magnetic and/or luminescence properties [23,25,26,27], we report here the synthesis, structures and magnetic properties of new such complexes bearing the monoanion of tris(2-hydroxyethyl)amine (the empirical name is triethanolamine, abbreviated hereafter as teaH3, Scheme 1). This ligand is very popular in 3d- and mixed 3d/4f-metal cluster chemistry (representative 3d/4f-metal compounds based on anionic forms of teaH3 are described in refs [28,29,30,31]), but with limited used in homometallic LnIII and LnII (LnII = EuII, YbII) chemistry. LnIII and LnII complexes containing only the neutral ligand are always mononuclear [32,33,34,35,36], whereas the doubly deprotonated form (teaH) of the ligand, either alone or with the simultaneous presence of other bridging inorganic or organic ligands, have led to high nuclearity LnIII clusters [37,38,39]. The singly deprotonated (teaH2) ligand has been employed only with combination with other bridging groups and such ligand “blends” give polynuclear LnIII complexes [38,39,40], although the teaH2 group usually (but not always) bridges two metal centers.

2. Results and Discussion

2.1. Synthetic Comments and IR Discussion

Since we were interested in isolating dinuclear lanthanide(III) complexes with the singly deprotonated form of triethanolamine, i.e., teaH2, as ligand, we avoided the addition of external bases (Et3N, LiOH, Me4NOH, etc.) in the systems. Previous reports have shown that use of Et3N in the LnIII/teaH3 reaction mixtures in MeOH and MeOH/CH2Cl2 lead to clusters [Ln6(NO3)6(teaH)6] [37] and [Ln8(OH)6(teaH)6(teaH2)2(teaH3)2](O3SCF3)4 [39], respectively, containing exclusively or partially the dianionic teaH2− ligand. We hoped that the formation of LnIII–O(teaH3) bonds in solution would lead to moderate polarization of the –CH2–CH2–O–H groups of teaH3 and subsequent single deprotonation of the ligand; this has, indeed, turned out to be the case. Thus, the 1:1 Ln(NO3)3·xH2O/teaH3 reaction mixtures in MeOH gave solutions from which were subsequently isolated crystals of the dinuclear complexes [Ln2(NO3)4(teaH2)2] (Ln = Pr, 1; Ln = Gd, 2; Ln = Tb, 3; Ln = Dy, 4; Ln = Ho, 5) in yields of ca. 50%. The crystals of 1, 2 and 4 (in the form of their bis-methanol solvates) were of X-ray quality and their structures were solved by single crystal X-ray crystallography. Complexes 3 and 5 (isolated as polycrystalline powders) are proposed to be isostructural with 1, 2 and 4 based on elemental analyses and IR spectra (vide supra), as well as on powder XRD patterns (vide infra, Figure S1) for 2, 3 and 4. Assuming that the dinuclear complexes are the only products from the general Ln(NO3)3·xH2O/teaH3 (1:1) reaction system in MeOH, their formation can by summarized by Equation (1), where x is 6 or 5:
2 Ln ( NO 3 ) 3 x H 2 O + 2 tea H 3 MeOH [ Ln 2 ( NO 3 ) 4 ( tea H 2 ) 2 ] + 2 H + + 2 NO 3 - + 2 x H 2 O 1 - 5
Analogous reactions in MeCN gave amorphous powders which we could not characterize.
In a next step, we examined the influence of the teaH3: LnIII reaction ratio on the product identity. Using an excess of the ligand, i.e., teaH3:Ln(NO3)3·xH2O molar ratios of 2.5:1, we anticipated the formation of complexes of the general formula [Ln2(NO3)2(teaH2)4]. Somewhat to our disappointment, the products of such reactions in MeOH with the lighter lanthanides are the mononuclear complexes [Ln(NO3)(teaH3)2](NO3)2, suggesting that the excess of teaH3 does not favor the efficient polarization (due to coordination) of the –CH2–CH2–O–H groups of the ligand that would lead to its single deprotonation. To fully characterize the mononuclear complexes, we have crystallized the representative PrIII complex and solved its structure (vide infra); its formation is summarized by Equation (2):
Pr ( NO 3 ) 3 6 H 2 O + 2 tea H 3 MeOH [ Pr ( NO 3 ) ( tea H 3 ) 2 ] ( NO 3 ) 2 + 6 H 2 O 6
IR evidence shows that the mononuclear complexes with the heavier lanthanide(III) ions, e.g., DyIII, HoIII and ErIII, are probably best formulated as eight-coordinate [Ln(teaH3)2](NO3)3 as a consequence of the lanthanide contraction. Since we were not particularly interested in mononuclear LnIII/teaH3 complexes, we did not pursue this chemistry further.
In the IR spectra of well-dried samples of complexes 15, the strong intensity broad band at ~3350 cm−1 is assigned to the ν(OH) vibration of the coordinated –OH groups of teaH2; this mode in the spectrum of 6 appears as two bands at ~3400 and 3230 cm−1 [41]. The broadness of the bands is indicative of the participation of the hydroxyl groups in H-bonding. The bands at ~1650 and 1473–1458 cm−1 are tentatively assigned to the δ(OH) and ν(C–C) modes, respectively. The KBr IR spectra of 15 exhibit a strong band at 1384 cm−1, characteristic of the ν3(Ε΄)[νd(N–O)] mode of the planar D3h ionic nitrate [42,43]; such a nitrate is absent in the complexes. The appearance of this band suggests that the nitrato ligands are replaced by bromides that are present in excess in the spectroscopic KBr matrix, thus producing ionic nitrates (KNO3); this replacement is facilitated by the pressure used for the preparation of the pellet [42,43]. In accordance with this conclusion, the band at 1384 cm−1 is absent from the mull spectra of these complexes. The mull IR bands at ~1480 and ~1290 cm−1 in 15 are assigned [25] to the ν1(A1)[ν(N=O)] and ν5(Β2)[νas(NO2)] vibrational modes, respectively, of the bidentate chelating (C2v) nitrato group. The separation of these two highest-wavenumber stretching bands (~190 cm−1) is large and typical of bidentate nitrates [25,42,43]. The KBr IR spectrum of 6 (which contains both chelating and ionic nitrates) exhibits only the ionic nitrate (D3h) band at 1383 cm−1 due to the bidentate nitrato group → ionic nitrate transformation mentioned above; however, the mull spectra (nujol and hexachlorobutadiene) show the typical bands of both the bidentate nitrato group (at 1490 and 1285 cm−1) and ionic nitrate (1383 cm−1), as expected. The IR spectra (KBr) of the representative dinuclear complex 3 and the free teaH3 ligand (liquid between CsI plates) are presented in Figures S2 and S3, respectively.

2.2. Description of Structures

The structures of 1·2MeOH, 2·2MeOH, 4·2MeOH and 6 have been solved by single-crystal X-ray crystallography (Table 1). Complexes 1·2MeOH, 2·2MeOH and 4·2MeOH are isomorphous and thus only the structure of 4·2MeOH will be described in detail. Complexes 3 and 5 are proposed to have similar structures with those of 1, 2 and 4 based on elemental analyses, IR spectra and powder X-ray patterns (Figure 1 and Figure S1). The measured pXRD patterns of 2, 3 and 4 are very similar indicating that the complexes are isostructural. The differences in intensity may be due to the preferred orientation of the crystalline powder samples [44,45]. The experimental patterns agree satisfactorily with those calculated from the single-crystal X-ray diffraction data. However, they are not identical; a possible reason for this is the fact that the measured patterns correspond to unsolvated complexes, i.e., 2, 3 and 4 (this is also confirmed by elemental analyses), while the simulated ones refer to the bis(methanol) solvates. Structural plots of the compounds 4·2MeOH and 6, as well as supramolecular features of complex 4∙2MeOH, are presented in Figure 2, Figure 3 and Figure 4, while numerical data are listed in Table 2 and Table 3 and Tables S1–S6. Structural plots of 1∙2MeOH and 2∙2MeOH are shown in Figures S4 and S5, respectively.
Complex 4·2MeOH crystallizes in the triclinic space group P 1 ¯ . Its structure consists of dinuclear [Dy2(NO3)4(teaH2)2] and solvate MeOH molecules in an 1:2 ratio; the latter will not be further discussed. The asymmetric unit contains half of the dinuclear complex molecule and one MeOH lattice solvent. The dinuclear molecule possesses an inversion center at the mid-point of the Dy1···Dy1΄ distance (3.669(1) Å). The two DyIII atoms are doubly bridged by the deprotonated oxygen atoms (O1, and O1΄) of the two η11122 teaH2 ligands (Scheme 1B). The teaH2 nitrogen atom (N1) and six terminal oxygen atoms (two from the neutral hydroxyl groups of the organic ligand and four from two slightly anisobidentate chelating nitrato groups) complete 9-coordination at each metal center. The Dy–O/N bond lengths are typical of nine-coordinate DyIII atoms [27,46]. The Dy1–O1,O1΄ bond lengths (2.265(1), and 2.236(1) Å) involving the deprotonated oxygen atoms are shorter than the Dy1–O2,O3 bond distances (2.363(1), and 2.466(2) Å) involving the neutral hydroxyl atoms of teaH2, as expected. Due to the bidentate coordination of the nitrato lligands, the N2–O6 (1.233(2) Å) and N3–O9 (1.216(2) Å) bond distances involving the “free”, i.e., uncoordinated, oxygen atoms are shorter than the N2–O4, O5 (1.261(2) Å) and N3–O7,O8 (1.263(2), and 1.280(2) Å) distances involving the coordinated oxygen atoms.
To estimate the closer coordination polyhedron defined by the donor atoms around Dy1 (and its centrosymmetric equivalent), a comparison of the experimental structural data with the theoretical data for the most common polyhedral structures with nine vertices was performed by means of the program SHAPE [47]. The so-called Continuous Shape Measures (CShM) approach essentially allows one to numerically evaluate by how much a particular structure deviates from an ideal shape. As there are no Platonic, Archimedean or Catalan polyhedra with nine vertices, and as no prisms or antiprisms can be constructed with an odd number of vertices, the main semiregular three-dimensional figures that may be considered are those listed (except, of course, the enneagon) in Table S1. The best fit (Table S1) was obtained for the spherical capped square antiprism (Figure S6), with the nitrato oxygen atom O4 being the capping atom.
The lattice structure of the complex is built through H bonds (Table S5) involving the MeOH oxygen atom (O1M) and the neutral hydroxyl oxygen atoms (O2, and O3) as donors, and the O1M, O3 and nitrato oxygen atoms O4 and O6 as acceptors; thus, O1M and O3 act as both donors and acceptors of H bonds. A weak, non-classical H bond is also formed with the teaH2 carbon atom C2 (this is the atom that is connected to N1) as donor and the nitrato oxygen atom O8 as acceptor. The O–H···O H bonds create chains parallel to the a axis (Figure 3).
The Ln–O/N bond lengths and the Ln···Ln distances in the isomorphous complexes 1·2MeOH, 2·2MeOH and 4·2MeOH follow the order Dy < Gd < Pr (for example the Dy···Dy, Gd···Gd and Pr···Pr distances are 3.669(1), 3.719(1) and 3.810(1) Å, respectively), a typical consequence of the lanthanide(III) contraction [25]. The coordination polyhedra of the GdIII (2·2MeOH) and PrIII (1·2MeOH) are closest to Johnson tricapped trigonal prism and to spherical-relaxed capped cube, respectively (Figures S7 and S8, respectively; Tables S2 and S3, respectively). At first glance, the fact that the LnIII centers in the isomorphous complexes 1∙2MeOH, 2∙2MeOH and 4∙2MeOH have different coordination geometries (and not consistent CShM values) seems strange. We attribute this to two factors: (i) For a given ligand set of nine donor atoms, the tricapped trigonal prism, capped square antiprism and capped cube polyhedra have comparable energies [48,49] and there exist minimal distortion interconversion paths between them; thus many structures are intermediate between two ideal shapes [48], and (ii) the LnIII-donor atom distances are slightly different due to lanthanide(III) contraction and this can affect the shape. For example, the CShM values of the DyIII center in 4∙2MeOH for the spherical capped square antiprism (3.263), spherical-relaxed capped cube (4.016) and tricapped trigonal prism (4.165) are all low and similar (Table S1), and its polyhedron could be equally well described as spherical-relaxed capped cube (a polyhedron that gives the lowest CShM value for the PrIII center in 1·2MeOH, Table S3).
Complex 6 crystallizes in the monoclinic space group C2/c. Its structure consists of mononuclear [Pr(NO3)(teaH3)2]2+ cations and NO3 counterions in a 1:2 ratio; the latter will not be further discussed. The asymmetric unit contains half of the cation and one nitrate anion. The cation has crystallographic twofold symmetry, with Pr1 and the nitrate atoms N2 and O5 occupying the rotation axis. Pr1 is coordinated to two neutral η1111 teaH3 ligands (A in Scheme 1) and to one bidentate chelating nitrato group, and its coordination number is thus 10. The Pr–O/N bond lengths are slightly shorter than the corresponding La–O/N ones in the isomorphous compound [La(NO3)(teaH3)2](NO3)2 [35]. Again, the N2–O5 (1.224(2) Å) bond distance involving the uncoordinated nitrato oxygen atom is shorter than the N2–O4, O4' distances (1.271(1) Å) involving the bound nitrato oxygen atoms.
Of the accessible 10-coordinate polyhedra for metal ions, the sphenocorona (tetradecahedron) (Figure 4b) is the most appropriate for the description of the 10 donor atoms in 6 according to the program SHAPE [47] (Table S4).
Intercationic interactions through the C3–HB(3)···O4 (and its symmetry equivalent) H bond result in the formation of chains parallel to the c axis (Figure 5a). Attached to these chains are lattice NO3 ions through the O1–H(O1)···O6 and O2–H(O2)···O8 H bonds (Figure 5a). These lattice NO3 ions interact further through the O3–H(O3)···O8 and C6–HA(C6)···O8–H bonds with neighboring chains forming a 3D architecture(Figure 5b). The dimensions of the H bonds are listed in Table S6.
Complexes 16 join a small family of homometallic LnIII complexes containing triethanolamine, and its singly and doubly deprotonated forms as ligands (Table 4); LnIII/tea3− complexes are not known. Complexes 1, 2 and 4 are the only dinuclear LnIII complexes that possess a form of triethanolamine as the only organic ligand. Complex 6 is isomorphous with [La(NO3)(teaH3)2](NO3)2 [35]. Of particular interest is the ability of teaH3 to stabilize homoleptic cationic complexes with the divalent lanthanides EuII and YbII [33,34].

2.3. Magnetic Susceptibility Studies

Direct current (dc) magnetic susceptibility data (χΜ) on dried polycrystalline, analytically pure samples of 25 were collected in the 2.0–300 K range. The data are plotted as χΜT vs. T products in Figure 6. The strength of the magnetic interactions between the two LnIII ions in the dinuclear complexes can be easily quantified with the gadolinium analog 2. Indeed, the GdIII ions present no spin-orbit coupling at the first order. Thus, the decrease or increase of the χΜT product when lowering the temperature for 2 reveals directly the presence of an antiferromagnetic or ferromagnetic, respectively, interaction between the GdIII centers. The room temperature χΜT value for 2 is 16.10 cm3∙K∙mol−1, essentially equal to the spin-only value (15.75 cm3∙K∙mol−1) expected for two non-interacting GdIII (8S7/2, S = 7/2, L = 0, g = 2) ions. The value of the χΜT product remains almost constant down to ~40 K and then decreases rapidly to 4.64 cm3∙K∙mol−1 at 2.0 K, suggesting an antiferromagnetic exchange interaction. Fit of the experimental data was performed by means of the conventional analytical expression derived from the isotropic spin Hamiltonian shown in Equation (3).
The best-fit parameters for the simultaneous simulation of susceptibility and magnetization data are J = −0.30(1) and g = 2.03 cm−1 with R values of 6.1 × 10−5ΜT) and 1.2 × 10−4 (M). As expected for pure LnIII systems, the exchange interaction is rather weak as a consequence of the shielded 4f orbitals that have small overlap with bridging ligand orbitals. This J value is typical for dinuclear complexes containing the {GdIII22-OR)2}4+ core [17,18,20,25,50]. Rov and Hughbanks performed a spin density functional (SDFT) study of dinuclear GdIII complexes containing the {Gd22-OR)2}4+ core [20]. The systematic study showed that symmetrically bridged complexes are antiferromagnetically coupled and asymmetrically bridged ones are ferromagnetically coupled. In the case of 2, the {Gd2III2-OR)2}4+ core shows near-D2h symmetry; the Gd–(μ2-OR) bond distances are nearly equal (2.258(1) and 2.303(1) Å) and the C– (μ2-Ο)–Gd angles are in the relatively narrow range 119.3(1)–130.5(1)°. Thus, the antiferromagnetic GdIII∙∙∙GdIII exchange interaction in 2 is in accordance with the theoretical predictions [20].
H ^ = - J ( S ^ Gd 1 S ^ Gd 1 )
The room temperature χΜT values for 3 (23.04 cm3∙K∙mol−1), 4 (28.07 cm3∙K∙mol−1) and 5 (29.32 cm3∙K∙mol−1) are in agreement with the expected theoretical values of 23.64, 28.34 and 28.14 cm3∙K∙mol−1 for two non-interacting TbIII (7F6, S = 3, L = 3, g = 3/2), DyIII (6H15/2, S = 5/2, L = 5, gj = 4/3) and HoIII (5I8, S = 2, L = 6, gj = 5/4) centers respectively. In all the three cases, the χΜT product decreases slightly between 300 and ~50 K, before a more rapid decrease below ~30 K, to reach values of 4.24(3), 9.52(4) and 11.02(5) cm3∙K∙mol−1 at 2.0 K. For such LnIII ions with an unquenched orbital moment associated with a ligand field, the decrease of the χΜT product as the temperature is lowered can originate from the following possible contributions [50]: (a) the thermal depopulation of the Stark sublevels; (b) the presence of magnetic anisotropy; and (c) antiferromagnetic interactions between the LnIII centers. The relatively low χΜT values at 2.0 K may suggest the contribution of a weak to moderate LnIII∙∙∙LnIII interaction (Ln = Tb, Dy, Ho), as confirmed for the GdIII2 complex 2. This assumption is further validated by the presence of a maximum in the χΜ vs. T plot at 3.3 K for the TbIII2 complex 3.
Magnetization plots for 25 are shown in Figure 7. As a consequence of the antiferromagnetic interaction between the spin carriers, the shape of the plots is clearly sigmoid for 2 and 3, this effect being less pronounced for 4 and almost negligible for the HoIII analog 5.
In order to investigate the presence of slow relaxation of the magnetization which might originate from an SMM behavior, alternating current (ac) magnetic susceptibility measurements were performed on powdered samples of 35 in the temperature range 2.0–12 K with zero dc field and a 4.0 G ac field oscillating in the 10-1500 Hz range. Unfortunately, no frequency dependent out-of-phase ( χ Μ ) signals were detected for the complexes. This was rather surprising for 4, because dysprosium(III) is a Kramers’ ion (it has an odd number of 4f electrons), meaning that the ground state will always be bistable (one of the prerequisites for a molecule to be an SMM) irrespective of the ligand field symmetry. A review by Rinehart and Long five years ago [51] has provided a lucid account of how f-element electronic structure can, in principle, be manipulated to create new SMMS. The basic overall shape of free-ion electron density is oblate (i.e., it extends into the xy plane) for TbIII, DyIII and HoIII in their ground states. Therefore, to maximize the anisotropy of an oblate ion (and thus the chances to observe SMM properties), we should place it in a crystal field for which the ligand electron density is concentrated above and below the xy plane; this is clearly not the case here. Given that in the absence of high symmetry (as in 4), the ground state of DyIII is a doublet along the anisotropy axis with an angular momentum quantum number mj = ±15/2, we have determined the orientation of the ground state magnetic anisotropy axis for the DyIII center of 4 using a method reported in 2013 [52], based on an electrostatic model. This method does not demand the fitting of experimental data; it only requires the knowledge of the single-crystal X-ray structure of the complex. Following this method and the program MAGELLAN (a FORTRAN program), the ground state magnetic anisotropy axis for each DyIII ion (the two axis are co-parallel due to the existence of the crystallographically imposed inversion center in the molecule) is directed towards the bridging oxygen atoms O1/O1΄ (Figure 8), which exhibit the shortest Dy–O bond distances (Table 2). This forces the oblate electron density of DyIII to be almost parallel to the easy axis, which is a non-favorable spatial conformation to achieve slow relaxation of the magnetization [52]. No frequency dependent out-of-phase ac magnetic susceptibility signals were observed for 35 under external dc fields of 0.1 and 0.2 T, suggesting that the complexes are not field-induced SMMs.
Since the LnIII ions most often used in SMMs are TbIII, DyIII, HoIII and ErIII (and rarely YbIII) and since there are no reports of PrIII SMMs [6], we have not studied the magnetic properties of the PrIII complexes 1 and 6.

3. Experimental Section

3.1. Materials and Physical Measurements

All manipulations were performed under aerobic conditions using reagents and solvents (Alfa Aesar, Aldrich; Karlsruhe, Germany and Tanfrichen, Germany, respectively) as received. Elemental analyses (C, H, N) were carried out by the University of Patras microanalytical service (Patras, Greece). FT-IR spectra (4000–400 cm−1) were recorded using a Perkin-Elmer (supplier, Watham, MA, USA) 16 PC FT-IR spectrometer with samples prepared as KBr pellets and as nujol or hexachlorobutadiene mulls between CsI disks. Solid state, variable-temperature direct-current (dc) magnetic susceptibility data were collected on powdered samples of representative complexes using a MPMS5 Quantum Design (supplier, San Diego, CA, USA) SQUID magnetometer, operating at dc fields of 0.3 T in the 300–30 K range and 0.03 T in the 30–2.0 K range to avoid saturation effects at low temperatures. Diamagnetic corrections were applied to observed paramagnetic susceptibilities using Pascal’s constants [53]. The fit of the experimental data for the dinuclear GdIII complex was performed with the PHI program [54]. The quality of the fits was parameterized using the factor R = {(χMT)exp − (χMT)calcd}2/{(χMT)exp}2.

3.2. Synthesis of [Pr2(NO3)4(teaH2)2]∙2MeOH (1∙2MeOH)

To a stirred colorless solution of teaH3 (66 μL, 0.50 mmol) in MeOH (20 mL) was added solid Pr(NO3)3∙6H2O (0.218 g, 0.50 mmol). The solid soon dissolved and the resulting very pale green (almost colorless) solution was stirred for a further 10 min and left undisturbed in a closed flask at room temperature. X-ray quality, pale green crystals of the product were formed over a period of 4–5 days. The crystals were collected by filtration, washed with cold MeOH (1 mL) and Et2O (3 × 1 mL), and dried in air. Typical yields were in the range 40%–45% (based on the PrIII available). The complex was satisfactorily analyzed as lattice MeOH-free, i.e., as 1. Anal calc. for C12H28N6Pr2O18 (found values in parentheses): C 17.44 (17.63), H 3.42 (3.36), N 10.17 (9.87)%. IR bands (KBr cm−1): 3356 sb, 3150 m, 2930 m, 1650 m, 1458 m, 1406 sh, 1384 s, 1094 m, 1084 m, 1064 w, 1032 m, 1004 m, 916 m, 832 w, 818 w, 738 w, 670 w, 564 m, 544 w, 526 w, 458 wb, 402 w.

3.3. Syntheses of [Gd2(NO3)4(teaH2)2]∙2MeOH (2∙2MeOH), [Tb2(NO3)4(teaH2)2]∙2MeOH (3∙2MeOH), [Dy2(NO3)4(teaH2)2]∙2MeOH (4∙2MeOH) and [Ho2(NO3)4(teaH2)2]∙2MeOH (5∙2MeOH)

These complexes were prepared and crystallized in an identical manner with 1∙2MeOH by simply replacing Pr(NO3)3∙6H2O with Gd(NO3)3∙6H2O (0.226 g, 0.50 mmol), Tb(NO3)3∙6H2O (0.227 g, 0.50 mmol), Dy(NO3)3∙5H2O (0.219 g, 0.50 mmol) and Ho(NO3)3∙6H2O (0.230 g, 0.50 mmol). The crystals of all the complexes were colorless. Typical yields were ~45% for 2, ~55% for 3, ~35% for 4 and ~40% for 5. The complexes were satisfactorily analyzed as lattice MeOH-free. Anal. calc. for C12H28N6Ln2O18 (found values in parentheses): 2 (Ln = Gd): C 16.78 (16.93), H 3.29 (3.40), N 9.79 (9.55)%; 3 (Ln = Tb): C 16.71 (16.39), H 3.28 (3.31), N 9.75 (9.50)%; 4 (Ln = Dy): C 16.58 (16.70), H 3.25 (3.37), N 9.67 (9.71)%; 5 (Ln = Ho): C 16.48 (16.31), H 3.23 (3.30), N 9.61 (9.42)%. The IR spectra of 2, 3, 4 and 5 are almost superimposable with the spectrum of 1 with a maximum wavenumber difference of ±4 cm−1.

3.4. Synthesis of [Pr(NO3)(teaH3)2](NO3)2 (6)

To a stirred colorless solution of teaH3 (330 μL, 2.50 mmol) in MeOH (12 mL) was added dropwise a solution of Pr(NO3)3∙6H2O (0.435 g, 1.00 mmol) in the same solvent (5 mL). The resulting very pale green (almost colorless) solution was stirred for a further 15 min. The undisturbed solution was allowed to slowly evaporate in an open flask at room temperature. X-ray quality, pale green crystals of the product were grown over a period of 2–3 d. When precipitation was judged to be complete, the crystals were collected by filtration, washed with cold MeOH (0.5 mL) and Et2O (5 × 1 mL), and dried in air. The yield was 62% (based on the PrIII available). Anal. calc. for C12H30N5PrO15 (found values in parentheses): C 23.05 (22.71), H 4.85 (4.97), N 11.20 (11.27)%. Characteristic IR bands (KBr, cm−1): ~3400 sb, 3230 m, 2940 m, 1643 m, 1473 m, 1010 m, 830 w.

3.5. Single-Crystal and Powder X-ray Crystallography

Suitable crystals of 1∙2MeOH, 2∙2MeOH, 4∙2MeOH and 6 had dimensions 0.12 × 0.18 × 0.36 mm, 0.10 × 0.17 × 0.20 mm, 0.10 × 0.26 × 0.44 mm and 0.10 × 0.16 × 0.39 mm, respectively. The crystals were taken from the mother liquor and immediately cooled to −113 °C (1∙2MeOH, 4∙2MeOH, 6) or to −43 °C (2∙2MeOH). Diffraction data were collected on a Rigaku (Tokyo, Japan) R-AXIS SPIDER Image Plate diffractometer using graphite-monochromated Mo Kα radiation. Data collection (ω-scans) and processing (cell refinement, data reduction and Empirical absorption correction) were performed using the CrystalClear program package [55]. Important crystallographic data are listed in Table 1. The structures were solved by direct methods using SHELXS-97 [56] and refined by full-matrix least-squares techniques on F2 with SHELXL-2014/6 [57]. Further experimental crystallographic details for 1∙2MeOH: 2θmax = 54.0°, 262 parameters refined, (Δ/σ)max = 0.002, (Δρ)max/(Δρ)min = 0.59/−0.44 e Å−3. Further experimental crystallographic details for 2∙2MeOH: 2θmax = 54.0°, 262 parameters refined, (Δ/σ)max = 0.003, (Δρ)max/(Δρ)min = 0.48/−0.52 e Å−3. Further experimental crystallographic details for 4∙2MeOH: 2θmax = 54.0°, 262 parameters refined, (Δ/σ)max = 0.002, (Δρ)max/(Δρ)min = 0.55/−0.54 e Å−3. Further experimental crystallographic details for 6: 2θmax = 54.0°, 203 parameters refined, (Δ/σ)max = 0.055, (Δρ)max/(Δρ)min = 0.46/−0.28 e Å−3. In the structure of 6, the methylene groups defined by the C1 and C2 atoms present disorder at two sites with 0.8 and 0.2 occupancies. All H atoms, except those of the disordered part in 6, were located by difference maps and were refined isotropically. All non-H atoms were refined anisotropically. Plots of the structures were drawn using the Diamond 3 program package [58]. The X-ray crystallographic data for the complexes in CIF formats have been deposited with CCDC (reference numbers CCDC 1522194, 1522195, 1522193 and 1522196 for 1∙2MeOH, 2∙2MeOH, 4∙2MeOH and 6, respectively). They can be obtained free of charge at http://www.ccdc.cam.ac.uk//conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK: Fax: +44-1223-336033; or e-mail: [email protected]. Powder X-ray diffraction patterns were collected on a Siemens D500 diffractometer (supplier, Zug, Switzerland) using Cu Kα radiation.

4. Conclusions and Perspectives

In this work, we have shown that the monoanion of triethanolamine can act as a bridging ligand forming dinuclear lanthanide(III) complexes of the general formula [Ln2(NO3)4(teaH2)2]. Five members of this family (Ln = Pr, Gd, Tb, Dy, Ho) have been fully characterized. Use of excess of the ligand leads to mononuclear [Ln(NO3)(teaH3)2](NO3)2 complexes with the early lanthanide(III) ions in which the ligand is neutral. Complexes 15 are the only dinuclear LnIII complexes that possess a form of triethanolamine as the only organic ligand. Magnetic studies have shown that the GdIII2 complex is characterized by weak to moderate intramolecular, antiferromagnetic exchange interaction; this is most probably the case for the TbIII2, DyIII2 and HoIII2 members of the family. The dinuclear complexes with the anisotropic LnIII atoms (Ln = Tb, Dy, Ho) do not exhibit SMM behavior; for the DyIII2 compound this has been rationalized by determining the metal ions’ magnetic anisotropy axes the direction of which forces the oblate electron density of DyIII to be almost parallel to the easy magnetization axis.
We are currently investigating the possibility to prepare LnIII complexes with the triply deprotonated form of triethanolamine, i.e., tea3−, as ligand; such compounds are not known to date (Table 4) and it is possible that tea3− can stabilize high-nuclearity LnIII compounds with interesting magnetic properties. Preliminary studies seem to confirm our expectations. As far as future perspectives are concerned, LnIII/RCO2/teaH2 compounds have never been reported and it is currently not known if these complexes are isostructural with 15 or the better (compared with the nitrate ion) bridging ability of simple carboxylates can lead to products with other structural types and nuclearities.

Supplementary Materials

The following are available online at https://www.mdpi.com/2312-7481/3/1/5/s1, Figure S1: X-ray powder diffraction patterns of complexes 3, 2 and 4. Figure S2: The IR spectrum (KBr, cm−1) of complex 3. Figure S3: The IR spectrum (liquid between CsI disks, cm−1) of the free teaH3 ligand. Figure S4: Partially labeled plot of the molecule [Pr2(NO3)4(teaH2)2] that is present in the structure of 1∙2MeOH. Figure S5: Partially labeled plot of the molecule [Gd2(NO3)4(teaH2)2] that is present in the structure of 2∙2MeOH. Figure S6: The spherical capped square antiprismatic coordination geometry of Dy1 in the structure of 4∙2MeOH. Figure S7: The Johnson tricapped trigonal prismatic coordination geometry of Gd1 in the structure of 2∙2MeOH. Figure S8: The spherical-relaxed capped cubic coordination geometry of Pr1 in the structure of 1∙2MeOH. Table S1: Continuous Shape Measures (CShM) values for the potential coordination polyhedra of Dy1/Dy1΄ in the structure of complex [Dy2(NO3)4(teaH2)2]∙2MeOH (4∙2MeOH). Table S2: Continuous Shape Measures (CShM) values for the potential coordination polyhedra of Gd1/Gd1΄ in the structure of complex [Gd2(NO3)4(teaH2)2]∙2MeOH (2∙2MeOH). Table S3: Continuous Shape Measures (CShM) values for the potential coordination polyhedra of Pr1/Pr1΄ in the structure of complex [Pr2(NO3)4(teaH2)2]∙2MeOH (1∙2MeOH). Table S4: Continuous Shape Measures (CShM) values for the potential coordination polyhedra of Pr1 in the structure of [Pr(NO3)(teaH3)2](NO3)2 (6). Table S5: H bonds in the crystal structure of complex [Dy2(NO3)4(teaH2)2]∙2MeOH (4∙2MeOH). Table S6: H bonds in the crystal structure of complex [Pr(NO3)(teaH3)2](NO3)2 (6).

Acknowledgments

Albert Escuer and Julia Mayans thank the Ministeria de Economía y Competitividad, Project CTQ2015-63614-P for funding. Spyros P. Perlepes thanks the COST Action: CA15128-Molecular Spintronics (MOLSPIN) for encouraging his group activities in Patras.

Author Contributions

Ioannis Mylonas-Margaritis and Stavroula-Melina Sakellakou conducted the syntheses, crystallization and conventional characterization of the complexes; the former also contributed to the interpretation of the results. Catherine P. Raptopoulou and Vassilis Psycharis collected crystallographic data, solved the structures and performed structures refinement; the latter also studied the supramolecular features of the crystal structures and wrote the relevant part of the paper. Julia Mayans and Albert Escuer performed the magnetic measurements, interpreted the results and calculated the magnetic anisotropy axes of the DyIII centers in complex 4∙2MeOH; the latter also wrote the relevant part of the paper. Spyros P. Perlepes coordinated the research, contributed to the interpretation of the results and wrote parts of the paper.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Luzon, J.; Sessoli, R. Lanthanides in molecular magnetism: So fascinating, so challenging. Dalton Trans. 2012, 41, 13556–13567. [Google Scholar] [CrossRef] [PubMed]
  2. Benelli, C.; Gatteschi, D. Magnetism of Lanthanides in Molecular Materials with Transition-Metal Ions and Organic Radicals. Chem. Rev. 2002, 102, 2369–2387. [Google Scholar] [CrossRef] [PubMed]
  3. Milios, C.J.; Winpenny, R.E.P. Cluster-Based Single-Molecule Magnets. Struct. Bond. 2015, 164, 1–109. [Google Scholar]
  4. For a review on Mn SMMs, see: Bagai, R.; Christou, G. The Drosophila of single-molecule magnetism: [Mn12O12(O2CR)16(H2O)4]. Chem. Soc. Rev. 2009, 38, 1011–1026. [Google Scholar] [CrossRef] [PubMed]
  5. Ishikawa, N.; Sugita, M.; Ishikawa, T.; Koshihara, S.-Y.; Kaizu, Y. Lanthanide Double-Decker Complexes Functioning as Magnets at the Single-Molecular Level. J. Am. Chem. Soc. 2003, 125, 8694–8695. [Google Scholar] [CrossRef] [PubMed]
  6. For an excellent and comprehensive review, see: Woodruff, D.N.; Winpenny, R.E.P.; Layfield, R.A. Lanthanide Single-Molecule Magnets. Chem. Rev. 2013, 113, 5110–5138. [Google Scholar] [CrossRef] [PubMed]
  7. Liddle, S.T.; van Slageren, J. Improving f-element single molecule magnets. Chem. Soc. Rev. 2015, 44, 6655–6669. [Google Scholar] [CrossRef] [PubMed]
  8. Li, K.; Zhang, X.; Meng, X.; Shi, W.; Cheng, P.; Powell, A.K. Constraining the coordination geometries of lanthanide centers and magnetic building blocks in frameworks: A new strategy for molecular nanomagnets. Chem. Soc. Rev. 2016, 45, 2423–2439. [Google Scholar] [CrossRef] [PubMed]
  9. Tang, J.; Zhang, P. Polynuclear lanthanide Single Molecule Magnets. In Lanthanides and Actinides in Molecular Magnetism, 1st ed.; Layfields, R.A., Murugesu, M., Eds.; Wiley-VCH: Berlin, Germany, 2015; pp. 61–88. [Google Scholar]
  10. Habib, E.; Murugesu, M. Lessons learned from dinuclear lanthanide nano-magnets. Chem. Soc. Rev. 2013, 42, 3278–3288. [Google Scholar] [CrossRef] [PubMed]
  11. Xue, S.; Guo, Y.-N.; Ungur, L.; Tang, J.; Chibotaru, L. Tuning the Magnetic Interactions and Relaxation Dynamics of Dy2 Single-Molecule Magnets. Chem. Eur. J. 2015, 21, 14099–14106. [Google Scholar] [CrossRef] [PubMed]
  12. Jiang, Y.; Brunet, G.; Holmberg, R.J.; Habib, F.; Karobkov, I.; Murugesu, M. Terminal solvent effects on the anisotropy barriers of Dy2 systems. Dalton Trans. 2016, 45, 16709–16715. [Google Scholar] [CrossRef] [PubMed]
  13. Xiong, J.; Ding, H.-Y.; Meng, Y.-S.; Gao, C.; Zhang, X.-J.; Meng, Z.-S.; Zhang, Y.-Q.; Shi, W.; Wang, B.-W.; Gao, S. Hydroxide-bridged five-coordinate DyIII single-molecule magnet exhibiting the record thermal relaxation barrier of magnetization among lanthanide-only dimmers. Chem. Sci. 2016. [Google Scholar] [CrossRef]
  14. Rinehart, J.D.; Fang, M.; Evans, W.J.; Long, J.R. Strong exchange and magnetic blocking in N23−-radical-bridged lanthanide complexes. Nat. Chem. 2011, 3, 538–542. [Google Scholar] [CrossRef] [PubMed]
  15. Guo, Y.-N.; Xu, G.-F.; Wernsdorfer, W.; Ungur, L.; Guo, Y.; Tang, J.; Zhang, H.-J.; Chibotaru, L.F. Strong Axiality and Ising Exchange Interaction Suppress Zero-Field Tunneling of Magnetization of an Asymmetric Dy2 Single-Molecule Magnet. J. Am. Chem. Soc. 2011, 133, 11948–11951. [Google Scholar] [CrossRef] [PubMed]
  16. Gao, F.; Li, Y.-Y.; Liu, C.-M.; Li, Y.-Z.; Zuo, J.-L. A sandwich-type triple-decker lanthanide complex with mixed phthalocyanine and Schiff base ligands. Dalton Trans. 2013, 42, 11043–11046. [Google Scholar] [CrossRef] [PubMed]
  17. Yi, X.; Bernot, K.; Cador, O.; Luzon, J.; Calvez, G.; Daiguebonne, C.; Guillou, O. Influence of ferromagnetic connection of Ising-type DyIII-based single ion magnets on their magnetic slow relaxation. Dalton Trans. 2013, 42, 6728–6731. [Google Scholar] [CrossRef] [PubMed]
  18. Nematirad, M.; Gee, W.J.; Langley, S.K.; Chilton, N.F.; Moubaraki, B.; Murray, K.S.; Batten, S.R. Single molecule magnetism in a μ-phenolato dinuclear motif ligated by heptadentate Schiff base ligands. Dalton Trans. 2012, 41, 13711–13715. [Google Scholar] [CrossRef] [PubMed]
  19. Xu, G.-F.; Wang, Q.-L.; Gamez, P.; Ma, Y.; Clérac, R.; Tang, J.; Yan, S.-P.; Cheng, P.; Liao, D.-Z. A promising new route towards single-molecule magnets based on the oxalate ligand. Chem. Commun. 2010, 46, 1506–1508. [Google Scholar] [CrossRef] [PubMed]
  20. Roy, L.E.; Hughbanks, T. Magnetic Coupling in Dinuclear Gd Complexes. J. Am. Chem. Soc. 2006, 128, 568–575. [Google Scholar] [CrossRef] [PubMed]
  21. Luis, F.; Repollés, A.; Martínez-Pérez, M.J.; Aguilà, D.; Roubeau, O.; Zueco, D.; Alonso, P.J.; Evangelisti, M.; Camón, A.; Sesé, J.; et al. Molecular Prototypes for Spin-Based CNOT and SWAP Quantum Gates. Phys. Rev. Lett. 2011, 107, 117203-1–117203-5. [Google Scholar] [CrossRef] [PubMed]
  22. Pedersen, K.S.; Ariciu, A.-M.; McAdams, S.; Weihe, H.; Bendix, J.; Tuna, F.; Piligkos, S. Towards Molecular 4f Single-Ion Magnet Qubits. J. Am. Chem. Soc. 2016, 138, 5801–5804. [Google Scholar] [CrossRef] [PubMed]
  23. For example, see: Anastasiadis, N.C.; Mylonas-Margaritis, I.; Psycharis, V.; Raptopoulou, C.P.; Kalofolias, D.A.; Milios, C.J.; Klouras, N.; Perlepes, S.P. Dinuclear, tetrakis(acetato)-bridged lanthanide(III) complexes from the use of 2-acetylpyridine hydrazone. Inorg. Chem. Commun. 2015, 51, 99–102. [Google Scholar] [CrossRef]
  24. Lin, P.-H.; Burchell, T.J.; Clérac, R.; Murugesu, M. Dinuclear Dysprosium(III) Single-Molecule Magnets with a large Anisotropic Barrier. Angew. Chem. Int. Ed. 2008, 47, 8848–8851. [Google Scholar] [CrossRef] [PubMed]
  25. Anastasiadis, N.C.; Kalofolias, D.A.; Philippidis, A.; Tzani, S.; Raptopoulou, C.P.; Psycharis, V.; Milios, C.J.; Escuer, A.; Perlepes, S.P. A family of dinuclear lanthanide(III) complexes from the use of a tridentate Schiff base. Dalton Trans. 2015, 44, 10200–10209. [Google Scholar] [CrossRef] [PubMed]
  26. Anastasiadis, N.C.; Granadeiro, C.M.; Klouras, N.; Cunha-Silva, L.; Raptopoulou, C.P.; Psycharis, V.; Bekiari, V.; Balula, S.S.; Escuer, A.; Perlepes, S.P. Dinuclear Lanthanide(III) Complexes by Metal-Ion-Assisted Hydration of Di-2-pyridyl Ketone Azine. Inorg. Chem. 2013, 52, 4145–4147. [Google Scholar] [CrossRef] [PubMed]
  27. Nikolaou, H.; Terzis, A.; Raptopoulou, C.P.; Psycharis, V.; Bekiari, V.; Perlepes, S.P. Unique Dinuclear, Tetrakis (nitrato-O,O′)-Bridged Lanthanide(III) Complexes from the Use of Pyridine-2-Amidoxime: Synthesis, Structural Studies and Spectroscopic Characterization. J. Surf. Interfaces Mater. 2014, 2, 311–318. [Google Scholar] [CrossRef]
  28. Murugesu, M.; Mishra, A.; Wernsdorfer, W.; Abboud, K.A.; Christou, G. Mixed 3d/4d and 3d/4f metal clusters: Tetranuclear FeIII2MIII2 (MIII = Ln, Y and MnIV2MIII2 (M = Yb,Y) complexes and the first Fe/4f single-molecule magnets. Polyhedron 2006, 25, 613–625. [Google Scholar] [CrossRef]
  29. Schray, D.; Abbas, G.; Lan, Y.; Mereacre, V.; Sundt, A.; Dreiser, J.; Waldmann, O.; Kostakis, G.E.; Anson, C.E.; Powell, A.K. Combined Magnetic Susceptibility Measurements and 57Fe Mössbauer Spectroscopy on a Ferromagnetic {FeIII4Dy4} Ring. Angew. Chem. Int. Ed. 2010, 49, 5185–5188. [Google Scholar] [CrossRef] [PubMed]
  30. Chilton, N.F.; Langley, S.K.; Moubaraki, B.; Murray, K.S. Synthesis, structural and magnetic studies of an isostructural family of mixed 3d/4f tetranuclear ‘star’ clusters. Chem. Commun. 2010, 46, 7787. [Google Scholar] [CrossRef] [PubMed]
  31. Langley, S.K.; Wielechowski, D.P.; Moubaraki, B.; Abrahams, B.F.; Murray, K.S. Magnetic Exchange Effects in {CrIII2DyIII2} Single Molecule Magnets Containing Alcoholamine Ligands. Aust. J. Chem. 2014, 67, 1581–1587. [Google Scholar] [CrossRef]
  32. Hahn, F.E.; Mohr, J. Synthese und Strukturen von Bis(triethanolamin)lanthanoid-Komplexen. Chem. Ber. 1990, 123, 481–484. [Google Scholar] [CrossRef]
  33. Starynowicz, P. Synthesis and structure of bis(triethanolamine)europium(II) diperchlorate. J. Alloy. Compd. 2001, 323–324, 159–163. [Google Scholar] [CrossRef]
  34. Starynowicz, P.; Gatner, K. An Ytterbium(II) Complex with Triethanolamine. Z. Anorg. Allg. Chem. 2003, 629, 722–726. [Google Scholar] [CrossRef]
  35. Fowkes, A.; Harrison, W.T.A. (Nitrato-κ2O, O′)bis(triethanolamine-κ4N, O,O′,O″)lanthanum(III) dinitrate. Acta Crystallogr. Sect. C 2006, 62, m232–m233. [Google Scholar] [CrossRef] [PubMed]
  36. Kumar, R.; Obrai, S.; Jassal, A.K.; Hundai, M.S. Supramolecular architectures of N, N, N′, N′-tetrakis(2-hydroxyethyl)ethylenediamine and tris(2-hydroxyethyl)amine with La(III) picrate. RSC Adv. 2014, 4, 59248–59264. [Google Scholar] [CrossRef]
  37. Langley, S.K.; Moubaraki, B.; Forsyth, G.M.; Gass, I.A.; Murray, K.S. Structure and magnetism of new lanthanide 6-wheel compounds utilizing triethanolamine as a stabilizing ligand. Dalton Trans. 2010, 39, 1705–1708. [Google Scholar] [CrossRef] [PubMed]
  38. Langley, S.K.; Moubaraki, B.; Murray, K.S. Magnetic Properties of Hexanuclear Lanthanide(III) Clusters Incorporating a Central μ6-Carbonate Ligand Derived from Atmospheric CO2 Fixation. Inorg. Chem. 2012, 51, 3947–3949. [Google Scholar] [CrossRef] [PubMed]
  39. Langley, S.K.; Moubaraki, B.; Murray, K.S. Trinuclear, octanuclear and decanuclear dysprosium(III) complexes: Synthesis, structural and magnetic studies. Polyhedron 2013, 64, 255–261. [Google Scholar] [CrossRef]
  40. Zhang, L.; Zhang, P.; Zhao, L.; Lin, S.-Y.; Xue, S.; Tang, J.; Liu, Z. Two Locally Chiral Dysprosium Compounds with Salen-Type Ligands That Show Slow Magnetic Relaxation Behaviour. Eur. J. Inorg. Chem. 2013, 1351–1357. [Google Scholar] [CrossRef]
  41. Naini, A.A.; Young, V.; Verkade, J.G. New complexes of Triethanolamine (TEA): Novel Structural Features of [Y(TEA)2](ClO4)3·3C5H5N and [Cd(TEA)2](NO3)2. Polyhedron 1995, 14, 393–400. [Google Scholar] [CrossRef]
  42. Tsantis, S.T.; Zagoraiou, E.; Savvidou, A.; Raptopoulou, C.P.; Psycharis, V.; Szyrwiel, L.; Holyńska, M.; Perlepes, S.P. Binding of oxime group to uranyl ion. Dalton Trans. 2016, 45, 9307–9319. [Google Scholar] [CrossRef] [PubMed]
  43. Kitos, A.A.; Efthymiou, C.G.; Manos, M.J.; Tasiopoulos, A.J.; Nastopoulos, V.; Escuer, A.; Perlepes, S.P. Interesting Copper(II)-assisted transformations of 2-acetylpyridine and 2-benzoylpyridine. Dalton Trans. 2016, 45, 1063–1077. [Google Scholar] [CrossRef] [PubMed]
  44. Hao, J.-M.; Yu, B.-Y.; Hecke, V.K.; Cui, G.-H. A series of d10 metal coordination polymers based on a flexible bis(2-methylbenzimidazole) ligand and different carboxylates: Synthesis, structures, photoluminescence and catalytic properties. CrystEngComm 2015, 17, 2279–2293. [Google Scholar] [CrossRef]
  45. Cui, G.-H.; He, C.-H.; Jiao, C.-H.; Geng, J.-C.; Blatov, V.A. Two metal-organic frameworks with unique high-connected binodal network topologies: Synthesis, structures, and catalytic properties. CrystEngComm 2012, 14, 4210–4216. [Google Scholar] [CrossRef]
  46. For example, see: Polyzou, C.D.; Nikolaou, H.; Papatriantafyllopoulou, C.; Psycharis, V.; Terzis, A.; Raptopoulou, C.P.; Escuer, A.; Perlepes, S.P. Employment of methyl 2-pyridyl ketone oxime in 3d/4f-metal chemistry: Dinuclear nickel(II)/lanthanide(III) species and complexes containing the metals in separate ions. Dalton Trans. 2012, 41, 13755–13764. [Google Scholar] [CrossRef] [PubMed]
  47. Llunell, M.; Casanova, D.; Girera, J.; Alemany, P.; Alvarez, S. SHAPE, Continuous Shape Measures Calculation, version 2.0; Universitat de Barcelona: Barcelona, Spain, 2010. [Google Scholar]
  48. Ruiz-Martínez, A.; Casanova, D.; Alvarez, S. Polyhedral Structures with an Odd Number of Vertices: Nine-Coordinate Metal Compounds. Chem. Eur. J. 2008, 14, 1291–1303. [Google Scholar] [CrossRef] [PubMed]
  49. Kepert, D.L. Inorganic Stereochemistry; Springer: Berlin, Germany, 1982; pp. 179–187. [Google Scholar]
  50. Long, J.; Habib, F.; Lin, P.-H.; Korobkov, I.; Enright, G.; Ungur, L.; Wernsdorfer, W.; Chibotaru, L.F.; Murugesu, M. Single-Molecule Magnet Behaviour for an Antiferromagnetically Superexchange-Coupled Dinuclear Dysprosium(III) Complex. J. Am. Chem. Soc. 2011, 133, 5319. [Google Scholar] [CrossRef] [PubMed]
  51. Rinehart, J.D.; Long, J.R. Exploiting single-ion anisotropy in the design of f-element single-molecule magnets. Chem. Sci. 2011, 2, 2078–2085. [Google Scholar] [CrossRef]
  52. Chilton, N.F.; Collison, D.; McInnes, E.J.I.; Winpenny, R.E.P.; Soncini, A. An electrostatic model for the determination of magnetic anisotropy in dysprosium complexes. Nat. Commun. 2013, 4, 2551–2557. [Google Scholar] [CrossRef] [PubMed]
  53. Kettle, S.F.A. Physical Inorganic Chemistry-A Coordination Chemistry Approach; Oxford University Press: Oxford, UK, 1998; pp. 462–465. [Google Scholar]
  54. Chilton, N.F.; Anderson, R.P.; Turner, L.D.; Soncini, A.; Murray, K.S. PHI: A Powerful New Program for the Analysis of Polynuclear d- and f-block Complexes. J. Comput. Chem. 2013, 34, 1164–1175. [Google Scholar] [CrossRef] [PubMed]
  55. CrystalClear, version 1.40; Rigaku/MSC: The Woodlands, TX, USA, 2005.
  56. Sheldrick, G.M. SHELXS 97, Program for Structure Solution; University of Göttingen: Göttingen, Germany, 1997. [Google Scholar]
  57. Sheldrick, G.M. Crystal structure refinement with SHELXL. Acta Crystallogr. Sect. C. 2005, 71, 3–8. [Google Scholar]
  58. DIAMOND, Crystal and Molecular Structure Visualization, version 3.1; Crystal Impact: Bonn, Germany.
Scheme 1. The structural formula of teaH3 (up, left) and the to date crystallographically established coordination modes of the: neutral (A); and monoanionic (BD) teaH2; and dianionic (EG) teaH2− ligands in homometallic LnII (Ln = Eu, Yb) and LnIII chemistry.
Scheme 1. The structural formula of teaH3 (up, left) and the to date crystallographically established coordination modes of the: neutral (A); and monoanionic (BD) teaH2; and dianionic (EG) teaH2− ligands in homometallic LnII (Ln = Eu, Yb) and LnIII chemistry.
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Figure 1. Experimental X-ray diffraction patterns of complexes 2 (cyan), 3 (green) and 4 (blue), and the theoretical pattern for complex 2 (black).
Figure 1. Experimental X-ray diffraction patterns of complexes 2 (cyan), 3 (green) and 4 (blue), and the theoretical pattern for complex 2 (black).
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Figure 2. Partially labeled plot of the molecule [Dy2(NO3)4(teaH2)2] that is present in the structure of 4·2MeOH. One lattice MeOH molecule is also shown. The thick dotted cyan line represents the O2–H(O2)···O1M H bond. Symmetry operation used to generate equivalent atoms: (') −x + 1, −y, −z + 1. Only the H atoms at O2 and O3 (and their centrosymmetric equivalents) are shown.
Figure 2. Partially labeled plot of the molecule [Dy2(NO3)4(teaH2)2] that is present in the structure of 4·2MeOH. One lattice MeOH molecule is also shown. The thick dotted cyan line represents the O2–H(O2)···O1M H bond. Symmetry operation used to generate equivalent atoms: (') −x + 1, −y, −z + 1. Only the H atoms at O2 and O3 (and their centrosymmetric equivalents) are shown.
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Figure 3. Chains of molecules formed parallel to the a axis in the crystal structure of 4·2MeOH. The thick dashed lines represent the O2–H(O2)···O1M (cyan), O1M–H(O1M)···O3 (light green), O3–H(O3)···O6 and O3–H(O3)···O4 (orange) H bonds.
Figure 3. Chains of molecules formed parallel to the a axis in the crystal structure of 4·2MeOH. The thick dashed lines represent the O2–H(O2)···O1M (cyan), O1M–H(O1M)···O3 (light green), O3–H(O3)···O6 and O3–H(O3)···O4 (orange) H bonds.
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Figure 4. (a) Labeled plot of the cation [Pr(NO3)(teaH3)2]2+ that is present in the structure of 6. Since the methylene groups of teaH3 defined by the C1 and C2 atoms present disorder at two sites, only the carbon atoms of the sites with the 0.8 occupancy have been drawn. Symmetry operation used to generate equivalent atoms: (') –x + 1, y, −z + 1/2. Only the H atoms of the hydroxyl groups are shown. (b) The sphenocoronal coordination geometry of Pr1 in the structure of 6. The plotted polyhedron is the ideal, best-fit polyhedron using the program SHAPE [47]. Primed and unprimed donor atoms are related by the symmetry operation –x + 1, y, −z + 1/2.
Figure 4. (a) Labeled plot of the cation [Pr(NO3)(teaH3)2]2+ that is present in the structure of 6. Since the methylene groups of teaH3 defined by the C1 and C2 atoms present disorder at two sites, only the carbon atoms of the sites with the 0.8 occupancy have been drawn. Symmetry operation used to generate equivalent atoms: (') –x + 1, y, −z + 1/2. Only the H atoms of the hydroxyl groups are shown. (b) The sphenocoronal coordination geometry of Pr1 in the structure of 6. The plotted polyhedron is the ideal, best-fit polyhedron using the program SHAPE [47]. Primed and unprimed donor atoms are related by the symmetry operation –x + 1, y, −z + 1/2.
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Figure 5. (a) Chains of [Pr(NO3)(teaH3)2]2+ cations and NO3 counterions parallel to the c axis in the crystal structure of 6. (b) 3D arrangement of chains in the crystal structure of 6. The thick dashed lines represent the C3–HB(C3)···O4 (orange), O1–H(O1)···O6 (cyan), O2–H(O2)···O8 (yellow), O3–H(O3)···O8 (dark green) and C6–HA(C6)···O8 (light green) H bonds.
Figure 5. (a) Chains of [Pr(NO3)(teaH3)2]2+ cations and NO3 counterions parallel to the c axis in the crystal structure of 6. (b) 3D arrangement of chains in the crystal structure of 6. The thick dashed lines represent the C3–HB(C3)···O4 (orange), O1–H(O1)···O6 (cyan), O2–H(O2)···O8 (yellow), O3–H(O3)···O8 (dark green) and C6–HA(C6)···O8 (light green) H bonds.
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Figure 6. χΜT vs. T plots for compounds 2 (open circles), 3 (solid squares), 4 (solid circles) and 5 (open diamonds). The solid line is the fit of the data to the theoretical model for the GdIII2 complex 2; see the text for the fit parameters.
Figure 6. χΜT vs. T plots for compounds 2 (open circles), 3 (solid squares), 4 (solid circles) and 5 (open diamonds). The solid line is the fit of the data to the theoretical model for the GdIII2 complex 2; see the text for the fit parameters.
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Figure 7. (a) Magnetization plots at 2.0 K for compounds 2 (open circles), 3 (solid squares), 4 (solid circles) and 5 (open diamonds). The solid line is the fit of the data to the theoretical model for the GdIII2 complex 2. (b) First derivative of the magnetization plots evidencing their sigmoid shape.
Figure 7. (a) Magnetization plots at 2.0 K for compounds 2 (open circles), 3 (solid squares), 4 (solid circles) and 5 (open diamonds). The solid line is the fit of the data to the theoretical model for the GdIII2 complex 2. (b) First derivative of the magnetization plots evidencing their sigmoid shape.
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Figure 8. Ground state magnetic anisotropy axis (green bars) for the two symmetry-related DyIII ions that are present in the molecule of 4.
Figure 8. Ground state magnetic anisotropy axis (green bars) for the two symmetry-related DyIII ions that are present in the molecule of 4.
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Table 1. Crystallographic data for complexes 1·2MeOH, 2·2MeOH, 4·2MeOH and 6.
Table 1. Crystallographic data for complexes 1·2MeOH, 2·2MeOH, 4·2MeOH and 6.
Parameter1·2MeOH2·2MeOH4·2MeOH6
FormulaC14H36N6Pr2O20C14H36N6Gd2O20C14H36N6Dy2O20C12H30N5PrO15
Formula weight890.31922.99933.49652.32
Crystal systemtriclinictriclinictriclinicmonoclinic
Space group P 1 ¯ P 1 ¯ P 1 ¯ C 2 / c
RadiationMo KαMo KαMo KαMo Kα
T/K160230160160
a8.3271(2)8.3299(4)8.2897(4)11.5500(2)
b8.6978(2)8.6424(4)8.6055(4)14.8428(3)
c10.3787(3)10.3733(5)10.2855(5)13.8550(3)
α/°86.893(1)86.964(2)86.892(1)90
β/°80.373(1)79.310(1)79.141(1)107.393(1)
γ/°84.632(1)84.494(2)84.532(1)90
V3737.30(3)729.96(6)716.83(6)2266.62(8)
Z1114
Dcalc/g·cm−32.0052.1002.1621.832
μ/mm−13.364.605.272.23
Reflns measured1502813695984521716
Reflns unique (Rint)3210(0.018)3184(0.024)3119(0.026)2463(0.021)
Reflns with I > 2σ(I)3143309930422424
GOF on F21.121.071.071.08
R1a [I > 2σ(I)]0.01290.01290.01420.0134
wR2 b (all data)0.03050.02920.03320.0347
a R 1 = ( | F o | - | F c | ) / ( | F o | ) ; b w R 2 = { [ w ( F O 2 - F c 2 ) 2 ] / [ w ( F O 2 ) 2 ] } 1 2 .
Table 2. Selected interatomic distances (Å) and bond angles (°) for the representative complex [Dy2(NO3)4(teaH2)2]·2MeOH (4·2MeOH).
Table 2. Selected interatomic distances (Å) and bond angles (°) for the representative complex [Dy2(NO3)4(teaH2)2]·2MeOH (4·2MeOH).
Interatomic Distances (Å) a
Dy1···Dy1'3.669(1)Dy1–O82.527(2)
Dy1–O12.265(1)Dy1–N12.653(2)
Dy1···O1'2.236(1)N2–O41.261(2)
Dy1–O22.363(1)N2–O51.261(2)
Dy1–O32.466(2)N2–O61.233(2)
Dy1–O42.564(2)N3–O71.280(2)
Dy1–O52.492(2)N3–O81.263(2)
Dy1–O72.463(2)N3–O91.216(2)
Bond Angles (Å) a
O1–Dy1–O1'70.8(1)O5–Dy1–O1122.3(1)
O1–Dy1–O295.5(1)O5–Dy1–O773.7(1)
O1–Dy1–O7157.3(1)O7–Dy1–O851.2(1)
O1'–Dy1–O3149.6(1)O8–Dy1–O567.7(1)
O2–Dy1–O5136.2(1)N1–Dy1–O265.8(1)
O2–Dy1–O778.4(1)N1–Dy1–O5144.5(1)
O3–Dy1–O577.9(1)Dy1–O1–Dy1'109.2(1)
O3-Dy1-O8114.8(1)O4–N2–O5117.4(2)
O4–Dy1–O550.4(1)O4–N2–O6120.9(2)
O4–Dy1–O7113.2(1)O5–N2–O6121.7(2)
a Symmetry operation used to generate equivalent atoms: (') −x + 1, −y, −z + 1.
Table 3. Selected bond lengths (Å) and angles (°) for complex [Pr(NO3)(teaH3)2](NO3)2.
Table 3. Selected bond lengths (Å) and angles (°) for complex [Pr(NO3)(teaH3)2](NO3)2.
Bond Lengths (Å)
Pr1–O12.514(1)N2–O51.224(2)
Pr1–O22.502(1)N1–C1A1.487(4)
Pr1–O32.521(1)C1A–C2A1.518(4)
Pr1–O42.584(1)C2A–O11.429(2)
Pr1–N12.743(1)C3–O21.434(2)
N2–O41.271(1)C5–O31.430(2)
Bond Angles (°) a
O1–Pr1–O2115.6(1)O4–Pr1–O4'49.6(1)
O1–Pr1–O377.1(1)O4–Pr1–N182.5(1)
O1–Pr1–O469.6(1)O4'–Pr1–N1122.5(1)
O1–Pr1–N163.4(1)O4–N2–O4'116.9(2)
O2–Pr1–O2'172.0(5)O4–N2–O5121.6(1)
O3–Pr1–O3'70.2(1)C1A–C2A–O1107.4(2)
N1–Pr1–Nq'154.1(1)C6–C5–O3108.1(1)
a Symmetry operation used to generate equivalent atoms: (') –x + 1, y, −z + 1/2.
Table 4. Crystallographically characterized homometallic LnII and LnIII complexes containing the teaH3, teaH2 and teaH2− groups as ligands.
Table 4. Crystallographically characterized homometallic LnII and LnIII complexes containing the teaH3, teaH2 and teaH2− groups as ligands.
Complex aCoordination Mode bCoordination PolyhedraRef.
[LnIII(teaH3)2](CF3SO3)3 (Ln = Pr, Yb, Lu)η1111 (Α)CSAPR j[32]
[LnII(teaH3)2](ClO4)2 (Ln = Eu, Yb)η1111 (Α)n.r. k, BCATAPR l[33,34]
[LnIII(NO3)(teaH3)2](NO3)2 (Ln = La, Pr)η1111 (Α)SPC m[35], this work
[LnIII(teaH3)2(H2O)2](pic)2 (Ln = La) cη1111 (Α)BCSASPR n[36]
[Ln6III(NO3)6(teaH3)6] (Ln = Gd, Dy)η11223 (Ε)SAPR o[37]
[Ln6III(CO3)(NO3)2(chp)7(teaH2)2(teaH)2(H2O)](NO3) (Ln = Gd, Tb, Dy) dη11133 (C) e11223 (E) fSAPR o, TCTPR p[38]
[Ln3III(OH)(teaH2)3(paa)3]Cl2 (Ln = Dy) gη11122 (B)SAPR o[39]
[Ln8III(OH)6(teaH)6(teaH2)2(teaH3)2](CF3SO3)4 (Ln = Dy)η11133 (G)f11122 (F) f, η1111 (A,D) hSAPR o, CSAPR j[39]
[Ln2III(L)(teaH2)6(o-van)(H2L)(H2O)](ClO4)2iη11122 (B)TCTPR p[40]
[Ln2III(NO3)4(teaH2)2] (Ln = Pr, Gd, Dy)η11122 (B)CCU q, TCTPR p (Ln = Gd), CSAPR j (Ln = Dy)this work
a Solvent molecules have been omitted; b See Scheme 1; c pic is the picrate anion; d chp is the anion of 6-chloro-2-hydroxypyridine; e For the teaH2 ligands; f For the teaH2− ligands; g paa is the anion of N-(2-pyridyl)acetoacetamide; h For both the teaH2 and teaH3 ligands; i H2L is the Schiff base N,N′-bis(3-methoxysalicylidene)-1,2-cyclohexanediamine, L2− is its dianionic form and o-van is the anion of 3-methoxysalicylaldehyde (ortho-vanillin); j Capped square antiprism; k For the Eu(II) complex; l Bicapped trigonal antiprism; m Sphenocorona; n Bicapped square antiprism; o Square antiprism; p Tricapped trigonal prism; q Capped cube (for the Pr2 complex).

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Mylonas-Margaritis, I.; Mayans, J.; Sakellakou, S.-M.; P. Raptopoulou, C.; Psycharis, V.; Escuer, A.; P. Perlepes, S. Using the Singly Deprotonated Triethanolamine to Prepare Dinuclear Lanthanide(III) Complexes: Synthesis, Structural Characterization and Magnetic Studies. Magnetochemistry 2017, 3, 5. https://doi.org/10.3390/magnetochemistry3010005

AMA Style

Mylonas-Margaritis I, Mayans J, Sakellakou S-M, P. Raptopoulou C, Psycharis V, Escuer A, P. Perlepes S. Using the Singly Deprotonated Triethanolamine to Prepare Dinuclear Lanthanide(III) Complexes: Synthesis, Structural Characterization and Magnetic Studies. Magnetochemistry. 2017; 3(1):5. https://doi.org/10.3390/magnetochemistry3010005

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Mylonas-Margaritis, Ioannis, Julia Mayans, Stavroula-Melina Sakellakou, Catherine P. Raptopoulou, Vassilis Psycharis, Albert Escuer, and Spyros P. Perlepes. 2017. "Using the Singly Deprotonated Triethanolamine to Prepare Dinuclear Lanthanide(III) Complexes: Synthesis, Structural Characterization and Magnetic Studies" Magnetochemistry 3, no. 1: 5. https://doi.org/10.3390/magnetochemistry3010005

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