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Article

Syntheses, Crystal Structures and Thermal Behaviors of Two Supramolecular Salamo-Type Cobalt(II) and Zinc(II) Complexes

by
Gang Li
,
Jing Hao
,
Ling-Zhi Liu
,
Wei-Min Zhou
and
Wen-Kui Dong
*
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China
*
Author to whom correspondence should be addressed.
Crystals 2017, 7(7), 217; https://doi.org/10.3390/cryst7070217
Submission received: 4 June 2017 / Revised: 3 July 2017 / Accepted: 5 July 2017 / Published: 12 July 2017
(This article belongs to the Section Crystal Engineering)
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Versions Notes

Abstract

:
This paper reports the syntheses of two new complexes, [Co(L1)(H2O)2] (1) and [{Zn(L2)(μ-OAc)Zn(n-PrOH)}2] (2), from asymmetric halogen-substituted Salamo-type ligands H2L1 and H3L2, respectively. Investigation of the crystal structure of complex 1 reveals that the complex includes one Co(II) ion, one (L1)2− unit and two coordinated water molecules. Complex 1 shows slightly distorted octahedral coordination geometry, forming an infinite 2D supramolecular structure by intermolecular hydrogen bond and π–π stacking interactions. Complex 2 contains four Zn(II)ions, two completely deprotonated (L2)3− moieties, two coordinated μ-OAc− ions and n-propanol molecules. The Zn(II) ions in complex 2 display slightly distorted trigonal bipyramidal or square pyramidal geometries.

Graphical Abstract

1. Introduction

Recently, increasing attention has also been absorbed in coordination chemistry of Salen-type N2O2 chelating metal complexes owing to their various kinds of functionalities [1,2,3,4,5,6,7,8]. A part of the metal complexes are used as host–guest chemistry [9,10,11,12,13,14,15,16,17], magnetism [18,19,20,21,22,23,24,25], electrochemistry [26,27], biological activities [28,29,30,31,32,33,34], optical properties [35,36,37,38,39,40,41,42,43], catalysis [44,45], molecular recognition [35,36,46,47], and so forth. It is clear that the architectures of coordination molecule comprise metal ions (and metal clusters) that serve the roles of nodes and organic ligands as bridges. These exhibits diverse infinite one-dimensional (1D), two-dimensional (2D) models with various exciting structural features, resulting coordination bonding, hydrogen bonding, aromatic π–π stacking interactions as well as van der Waals forces [48].
Salen-type N2O2compounds are capable of forming different types of complexes due to their several electron-rich donor centers [49] and the tautomerism effect of the enol and keto forms [50]. Meanwhile, on account of the fact that the high electronegative oxygen atoms affect azomethine nitrogen and N2O2 coordination plane on the basis of Salamo-type bisoxime ligands [45,51,52,53,54,55], many complexes exhibit abundant interests, attractive structures and properties have been well documented [56,57,58,59]. Furthermore, metal ions play key roles in wide range of differing biological processes and the interaction of the metal ion with drugs employed for therapeutic reasons is a subject of considerable interest [60]. Herein, following our previous studies on the syntheses, structural characterizations and optical properties of Salamo-type complexes with the d5 and d10 group elements [49,61], we report the syntheses and structural characterizations of mononuclear Co(II) and tetranuclear Zn(II) complexes, [Co(L1)(H2O)2] (1), [{Zn(L2)(μ-OAc)Zn(n-PrOH)}2] (2) based on Salamo-type N2O2/N2O3ligands (H2L1 = 4,6-dibromo-4′,6′-dichloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol; H3L2 = 6-hydroxy-4′-chloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol), and the molar conductance, IR, UV-Vis spectra, TG-DTG and X-ray crystal structures were also investigated.

2. Experimental

Crystallographic data have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication, No. CCDC 1511309 and 1511310 for complexes 1 and 2. Copies of these data can be obtained free of charge on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK (Telephone: (44) 01223 762910; Fax: +44-1223-336033; E-mail: [email protected]). These data can also be obtained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html.

2.1. Materials and Methods

3,5-Dichlorosalicylaldehyde, 3,5-dibromosalicylaldehyde, 5-chlorosalicylaldehyde and 3-hydroxysalicylaldehyde were purchased from a Acros Organics company (New York, NY, USA) and used without further purification. The other reagents and solvents were analytical grade acquired from Tanjin Chemical Reagent Factory (Tianjin, China).
C, H, and N analyses were obtained using a GmbH VarioEL V3.00 automatic elemental analysis instrument (Berlin, Germany). Elemental analyses for Co(II) and Zn(II) were detected by an IRIS ER/S·WP-1 ICP atomic emission spectrometer (Berlin, Germany). Molar conductance value measurements were carried out on a model DDS-11D type conductivity bridge (The United States CHI)using 1.0 × 10−3 mol∙L−3 solution in DMF at 18 °C. IR spectra were recorded on a Vertex70 FT-IR spectrophotometer (Bruker AVANCE, Billerica, MA, USA), with samples prepared as KBr (400–4000 cm−1) pellets. UV–Vis absorption spectra were recorded on a Shimadzu UV-2550 spectrophotometer (Shimadzu, Japan) in ethanolic solution. 1H NMR spectra were determined by a German Bruker AVANCE DRX-400 spectrometer (Bruker AVANCE, Billerica, MA, USA). DSC-TG analyses were carried out at a heating rate of 10 °C/min on a NETZSCH STA 449 F3 thermoanalyzer (NETZSCH Group, Germany). X-ray single crystal structures were determined on a Bruker Smart APEX CCD area detector (Bruker AVANCE, Billerica, MA, USA). Melting points were measured by the use of a microscopic melting point apparatus made in Beijing Taike Instrument Limited Company, and the thermometer was uncorrected.

2.2. Synthesis of H2L1

The major reaction step, containing the synthesis of 4,6-dibromo-4′,6′-dichloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H2L1) and 6-hydroxy-4′-chloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H3L2), is given in Scheme 1.
1,2-Bis(aminooxy)ethane was prepared by an analogous method reported earlier [35,36]. Yield: 56.8%. Anal. Calcd for C2H8N2O2 (%): C, 26.08; H, 8.76; N, 30.42. Found: C, 25.97; H, 8.70; N, 30.49.
2-[O-(1-ethyloxyamide)]oxime-4,6-dichlorophenol: A solution of 3,5-dichlorosalicylaldehyde (382.02 mg, 2.0 mmol) in ethanol (40 mL) was added to a solution of 1,2-bis(aminooxy)ethane (368.4 mg, 4.0 mmol) in ethanol (100 mL), then the mixture was subjected to heating at 50–55 °C for 6 h. The solution was concentrated in vacuo and the residue was purified by column chromatography (SiO2, chloroform/ethyl acetate, 25:1) to afford crystals of 2-[O-(1-ethyloxyamide)]oxime-4,6-dichlorophenol. Yield: 65.6%, m.p. 92–93 °C. Anal. Calcd for C9H10Cl2N2O3 (%): C, 40.78; H, 3.80; N, 10.57. Found: C, 40.72; H, 3.69; N, 10.63.
4,6-Dibromo-4′,6′-dichloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenl (H2L1): A solution of the obtained 2-[O-(1-ethyloxyamide)]oxime-4,6-dichlorophenol (384.38 mg, 1.45 mmol) in ethanol (15 mL) was added to a solution of 3,5-dibromosalicylaldehyde (406.00 mg, 1.45 mmol) in ethanol (15 mL) and the mixture was subjected to heating at 50–55 °C for 8 h. After cooling to room temperature, the resulting white precipitates were collected. Yield: 79.8%, m.p. 184–185 °C. 1H NMR (400 MHz, CDCl3) δ 10.48 (s, 1H), 10.32 (s, 1H), 8.15 (d, J = 10.5 Hz, 2H), 7.65 (d, J = 2.2 Hz, 1H), 7.37 (d, J = 2.4 Hz, 1H), 7.25 (s, 1H), 7.08 (d, J = 2.4 Hz, 1H), 4.48 (d, J = 20.8 Hz, 4H). Anal. Calcd for C16H12Br2Cl2N2O4 (%): C, 36.47; H, 2.30; N, 5.32. Found: C, 36.40; H, 2.35; N, 5.29.

2.3. Synthesis of H3L2

2-[O-(1-ethyloxyamide)]oxime-4-chlorophenol: A solution of 5-chlorosalicylaldehyde (314.00 mg, 2.0 mmol) in ethanol (50 mL) was added to a solution of 1,2-bis(aminooxy)ethane (368.00 mg, 4.0 mmol) in ethanol (100 mL) and the mixture was subjected to heating at 50–55 °C for 6 h. The solution was concentrated in vacuo and the residue was purified by column chromatography (SiO2, chloroform/ethyl acetate, 20:1) to afford crystals of 2-[O-(1-ethyloxyamide)]oxime-4-chlorophenol. Yield: 59.9%, m.p. 70–71 °C. Anal. Calcd for C9H11ClN2O3 (%): C, 46.87; H, 4.81; N, 15.37. Found: C, 46.80; H, 4.90; N, 15.32.
6-Hydroxy-4′-chloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol (H3L2): A solution of the obtained 2-[O-(1-ethyloxyamide)]oxime-4-chlorophenol (385.77 mg, 1.67 mmol) in ethanol (15 mL) was added to a solution of 3-hydroxysalicylaldehyde (234.60 mg, 1.70 mmol) in ethanol (20 mL) and the mixture was subjected to heating at 50–55 °C for 6 h. After cooling to room temperature, white precipitates of the desired product were collected. Yield: 80.7%, m.p. 132–133 °C. 1H NMR (400 MHz, CDCl3) δ 4.43 (d, J = 19.6 Hz, 4H), 7.12 (s, 1H), 7.39 (d, J = 2.5 Hz, 2H), 7.48 (d, J = 2.4 Hz, 2H), 7.57 (s, 1H), 7.69 (d, J = 2.5, Hz, 2H), 8.02 (s, 1H), 8.34 (s, 1H), 8.41 (s, 1H). Anal. Calcd for C16H15ClN2O5 (%): C, 54.79; H, 4.31; N, 7.99. Found: C, 54.67; H, 4.36; N, 8.01.

2.4. Synthesis of Complex 1

A pink, transparent n-propanol solution (2 mL) of cobalt(II) acetate tetrahydrate (3.30 mg, 0.013 mmol) was added dropwise to a colorless mixed solution of CH2Cl2 and CH3CN (4 mL) of H2L1 (3.85 mg, 0.007 mmol) at room temperature. The color of the mixed solution turned to yellow immediately, the filtrate was allowed to stand at room temperature for about two weeks, after which light-yellow prismatical single crystals suitable for X-ray structural determination were obtained by the slow evaporation from mixed solution. Anal. Calcd for C16H14Br2Cl2CoN2O6 (%): C, 31.00; H, 2.28; N, 4.52; Co, 9.51. Found: C, 29.88; H, 2.26; N, 4.60; Co, 9.48.

2.5. Synthesis of Complex 2

A colorless, transparent n-propanol solution (2 mL) of zinc(II) acetate tetrahydrate (4.51 mg, 0.021 mmol) was added dropwise to a colorless acetonitrile solution (4 mL) of H3L2 (3.49 mg, 0.010 mmol) at room temperature. The color of the mixing solution was immediately turned to yellow, and the filtrate was left to stand at room temperature for about two weeks, after which light-yellow prismatical single crystals suitable for X-ray structural determination were obtained by the slow evaporation from mixed solution. Anal. Calcd for C42H46Cl2N4O16Zn4 (%): C, 42.20; H, 3.88; N, 4.69; Zn, 21.88. Found: C, 42.16; H, 3.84; N, 4.70; Zn, 21.79.

2.6. Crystal Structure Determinations of Complexes 1 and 2

Single crystal X-ray diffraction data of complexes 1 and 2 were collected at 293(2) and 228(3) K, respectively, on a BRUKER SMART APEX II CCD diffractometer with graphite monochromated Mo-Kα radiation (λ = 0.71073 Å). The LP factor semi-empirical absorption corrections were applied using the SADABS program. The structures were solved by direct methods using SHELXS and refinement was done against F2 using SHELXL. The non-hydrogen atoms were refined anisotropically; hydrogen atoms were positioned geometrically (C–H = 0.93, 0.96 and 0.97 Å) and were refined as riding, with Uiso(H) = 1.20 or 1.50 Ueq(C). The crystal data and experimental parameters relevant to the structure determinations are listed in Table 1 and the final positional and thermal parameters are available as Supplementary Materials.

3. Results and Discussion

Complexes 1 and 2 with the Salamo-type bisoxime chelating N2O2/N2O3ligands (H2L1 and H3L2) have been duly synthesized, and structurally characterized by molar conductance, IR spectra, UV-Vis spectra, DSC-TG and X-ray crystallography analyses.

3.1. Molar Conductance

Complexes 1 and 2 are both soluble in DMF and DMSO, but insoluble in CHCl3, CH2Cl2, EtOH, MeOH, MeCN, THF, acetone, ethyl acetate and n-hexane. Only complex 1 displays good stability in air at room temperature while complex 2 shows relative instability. Moreover, the ligands (H2L1 and H3L2) are both soluble in the above solvents. The molar conductance values of complexes 1 and 2 in 1.0 × 10−3 mol∙L−3 DMF solutions are 2.2 and 2.9 Ω−1∙cm2∙mol−1, respectively, with the implication that complexes 1 and 2 are non-electrolytes.

3.2. Crystal Structure of Complex 1

The results of the X-ray structural study reveal that complex 1 crystallizes in the monoclinic system and P2(1)/c space group. As depicted in Figure 1, complex 1 concludes one Co(II) ion together with one deprotonated ligand (L1)2− unit (in the form of enol), and two coordinated water molecules. The Co(II) ion is hexa-coordinated by two oxime nitrogen (N1 and N2) atoms and two deprotonated phenoxo oxygen (O1 and O4) atoms, the four atoms are all from one deprotonated (L1)2− unit, and two oxygen (O5 and O6) atoms from two coordinated water molecules. The coordination environment around the Co(II) ion is best described as a slightly distorted octahedral geometry (Figure 1). This shows a correlation to the reported trinuclear [Co3(5-NO2salamo)2(OAc)2(MeOH)2]·2MeOH, in which the Co(II) ions of the trinuclear complex are all slightly distorted octahedral geometries with hexacoordination [54]. Unlike the mononuclear complex [Co(salen)], the Co(II) ion is a distorted square planar geometry with tetracoordination [56]. Whereas the Co(II) ion of trinuclear complex [Co3(salamo)2(OAc)2]·THF with parent Salamo ligand exhibits two different coordination geometries, the terminal Co(II) ions possess pentacoordinated square pyramidal geometries; nevertheless, the central Co(II) ion has a hexacoordinated octahedral geometry [59]. It is obvious that the eight Co(II) ions of an octanuclear Co(II) cluster[Co8(3-OHSalamo)4(H2O)2X]·2H2O·1.5CHCl3·0.5hexane (X = H2O or EtOH) are all pentacoordinated. The geometries around four outer Co(II) ions (Co1, Co2, Co3 and Co4) are trigonal bipyramidal (τ = 0.788–0.862). One of the inner Co(II) ions (Co6) has an intermediate geometry between trigonal bipyramidal and square pyramidal (τ = 0.521), however, Co8 is square pyramidal (τ = 0.083) and Co5 and Co7 are distorted one (τ = 0.274, 0.308).
(L1)2− unit of complex 1 acts as a tetradentate agent through two phenolic oxygen and oxime nitrogen atoms, which are in the equatorial positions. The four N2O2 donor atoms of (L1)2− unit are approximately coplanar, and the dihedral angle of N1–N2–O4 and N2–O1–O4 is about 0.58(2)°. The axial sites are filled up by two water molecules in a relatively large angle of O5-Co(II)-O6 (175.33(12)°). It is explicit that the bond distance Co1–O5 (2.141(2) Å) shows a more significant length than that of Co1–O6 (2.124(2) Å), and this reveals the varied coordination abilities of the two coordinated water molecules (Table 2). TheCo(II)ion of complex 1 is almost coplanar with the mean plane through the N2O2 core, diverging from the mean plane by 0.028 Å and the four donor atoms (N1, N2, O1 and O4) from their mean plane by 0.008, −0.008, −0.008 and 0.008 Å. Thus, the octahedral Co(II) center is composed of the N2O2 coordination sphere made up of (L1)2− unit in the equatorial plane and two coordinated water molecules. The seven-membered chelate ring (Co–N1–O2–C8–C9–O3–N2) in complex 1 is in a gauche conformation with the ethylene carbon atoms above the N2O2 coordination plane (C8, 0.502 Å and C9, 1.148 Å). The Co–O(phenolic) bonds of 2.083(3) Å and 2.062(3) Å and Co–N(oxime) bonds of 2.088(4) Å and 2.123(4) Å are in conformity with the average bond lengths observed for the corresponding bonds in the Co(II) complexes that anchors tetradentate Salamo-type ligands [62].
The crystal structures of complex 1 were linked by intermolecular O5–H5B⋅⋅⋅O4, O6–H6A⋅⋅⋅O1, C8–H8B⋅⋅⋅O2 and C9–H9B⋅⋅⋅O3 hydrogen bonding and weaker π⋅⋅⋅π (Ph) stacking interactions existing between adjacent phenyl rings (Table 3 and Table 4) [17], which perform a crucial role in constructing and stabilizing supramolecular structure. The oxygen O2 (O3) atoms of the N2O2 molecules are hydrogen bonded to the C8–H8B (C9–H9B) groups of another complex molecule linking adjacent complex molecules into an infinite 2D supramolecular structure (Figure 2) [63,64,65,66,67].

3.3. Crystal Structure of Complex 2

Complex 2 crystallizes in the triclinic system and P-1 space group. As shown in Figure 3, the structure of complex 2 is made up of four Zn(II) ions, two deprotonated (L2)3− units (in the form of enol), two μ-acetate ions and two coordinated n-PrOH molecules, showing consistency with the analytical data. The terminal Zn(II) (Zn1) ion is pentacoordinated by two oxime nitrogen (N1 and N2) atoms and two phenoxo oxygen (O1 and O5) atoms of one deprotonated (L2)3− unit, and one oxygen (O6) atom of one μ-acetate ion, displaying a slightly distorted trigonal bipyramidal coordination motif (τ = 0.704) (Figure 3). Meanwhile, the other Zn(II) (Zn2) ion is pentacoordinated by three phenoxo oxygen (O4, O4i and O5) atoms of two tetradentate deprotonated (L2)3− units, one carbonyl oxygen (O7) atom from the μ-acetate ion as well as one hydroxyl oxygen (O8) atom from one coordinated n-Pr-OH molecule. The coordination geometry around the Zn(II) (Zn2) ion can be described as a slightly distorted square pyramidal coordination sphere (τ = 0.178) (Figure 3). This tetranuclear Zn(II) complex is rare case for Salen- or Salamo-type complexes, showing that the complexation of 3-hydroxy Salamo-type ligands with Zn(II) acetate occurs cooperatively [57], unlike in the case of other substituted Salen- [32,33,34] or Salamo-type ligands [35,36]. In fact, this tetranuclear Zn(II) complex exhibits a similar structure to the Zn(II) complex previously reported [35]. The description of the tetranuclear structure is two [Zn(L2)(μ-OAc)Zn(n-PrOH)] units connected with two diphenoxy-bridges. In each of the units, the Zn1 center was coordinated via N2O2 donors. The central Zn2 was coordinated by three deprotonated μ-phenolic oxygen atoms in two [Zn(L2)] chelates and one oxygen atom of coordinated n-propanol molecule. The acetate ion was coordinated to two Zn(II) ions through Zn1–O–C–O–Zn2 bridge. Thus, the complex is composed of four five-coordinated Zn(II) centers, alike with the coordination geometries of Zn(II) ions in the literature predecent [57]. This is attributed to the difference in the bond lengths and angles between the central ion, and the coordination groups, as well as the distortions of the geometries of the Zn(II) centers.

3.4. IR Spectra

The FT-IR spectra of H2L1 and H3L2 and their corresponding complexes 1 and 2 exhibit various bands in the 4000–400 cm−1 region. Figure 4 shows the most important FT-IR bands for H2L1 and H3L2 and complexes 1 and 2.
In general, the O-H stretching frequency of Salen-type ligand appears at approximately 3433 cm−1 owing to the intramolecuar OH···N=C hydrogen bonding [59], the absorption commonly appears in the FT-IR spectrum as a broad or double band and occasionally, the band seems to be undetectable. Disappearance of the band is expected for the metal complexes as a result of the substitution reaction when the OH hydrogen is substituted or replaced by the metal ions, thus leading to the complex formation [60].
At 1613 and 1612 cm−1, the free ligands H2L1 and H3L2 show typical C=N stretching bands, while complexes 1 and 2 exhibit the characteristic C=N bands at 1609 and 1604 cm−1, respectively. Upon complexation, shifts to lower frequencies by ca. 4 and 8 cm−1 [52] are observed in the C=N stretching frequencies for complexes 1 and 2, respectively, indicating a decrease in the C=N bond order owing to the effects of the coordinated bonds of Co(II) and Zn(II) ions with the lone pair of oxime nitrogen electrons [61]. As reported, the Ar-O stretching frequency in the 1216–1213 cm−1 range appears as a strong band [60]. These bands occur at 1270 and 1264 cm−1 for the ligands H2L1 and H3L2, and at 1209 and 1203 cm−1 for complexes 1 and 2, respectively. The Ar-O stretching frequencies are shifted to a lower frequency, indicating that the Co(II)-O and Zn(II)-O bonds were formed between the Co(II) and Zn(II) ions and oxygen of phenolic group [61].
The typical absorption bands at 3413, 1643, and 519 cm−1 in complex 1 are assigned to the coordinated water molecules as are substantiated by crystal structure. The IR spectrum of complex 2 shows the expected strong absorption band due to νO-H at ca. 3450 cm−1, which is evident for the existence of n-propanol molecule.

3.5. UV-Vis Spectra

The absorption spectra of ligands H2L1 and H3L2 and their corresponding complexes 1 and 2 were determined in 5 × 10−5 mol·L−1 ethanolic solution (Figure 5). Obviously, the absorption peaks of the ligands H2L1 and H3L2 differ from those of complexes 1 and 2 upon complexation. The electronic absorption spectrum of the Salamo-type ligand H2L1 consists of three relatively intense bands centered at 225, 268 and 325 nm (for H3L2, 219, 270 and 321 nm), which may be assigned to the π–π* transitions of the phenyl of salicylaldehyde and the oxime group [58]. The absorption bands at 268 and 325 nm (for H3L2, 270 nm) disappear from the UV-vis spectrum upon complexation of the ligand with the metal ions, and indicates that the oxime nitrogen atoms are involved in coordination. The phenyl of salicylaldehyde intraligand π–π transition is a little shifted to 236 and 214 nm in the corresponding complexes 1 and 2, respectively. Besides, the newly emerged band observed at 377 nm for complex 1 is assigned to the L→M charge-transfer transition, which is typical of the transition metal complexes with N2O2 coordination spheres [68].

3.6. Thermal Properties

Thermal stability studies were performed for complexes 1 and 2. The TG curve of complex 1 occurs in two stages. The first stage is between 132 and 176 °C. The TG curve shows a 6.0% weight loss in this temperature range, which is roughly similar to the 5.8% value calculated for the loss of two coordinated water molecule from the outer coordination sphere of complex 1. Then, the remaining solid residue was stable up to around 207 °C, after which the compound begins to decompose. At 800 °C, the TG curve shows an approximately 88.3% total mass loss, indicating the complete removal of the (L1)2− unit. The main residual product was CoO, with a value of 11.7% (theoretical residual value was 12.1%).
The TG curve of complex 2 occurred in three stages. The first stage occurs in the 187–215 °C range. The TG curve indicates that the weight loss corresponding to this temperature range is 10.4%, which is roughly similar to the 10.1% value estimated for the loss of two coordinated n-PrOH molecules from the inner coordination sphere of complex 2. The second stage starts from 256 °C with a weight loss of 9.7%, which corresponds to the loss of two μ-acetate (theoretical mass loss, 9.9%) ions. Finally, the third weight loss starts at around 283 °C, leading to the full decomposition of the compound. At 650 °C, the TG curve shows about 92.8% total mass loss, indicating the complete removal of the (L2)3− unit. The main residual product was ZnO, with a value of 7.2% (theoretical residual value was 6.8%).

4. Conclusions

In conclusion, according to the confirmed data, two new complexes with the chemical formulae [Co(L1)(H2O)2] (1) and [{Zn(L2)(μ-OAc)Zn(n-PrOH)}2] (2) were synthesized and structurally characterized by IR, UV-Vis spectra, TG-DTA and X-ray crystallography analyses, where H2L1 and H3L2 are 4,6-dibromo-4′,6′-dichloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol and 6-hydroxy-4′-chloro-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol, respectively. The asymmetric unit of complex 1 contains a [CoL1] unit with 2 axially coordinated water ligands completing the coordination sphere, showing slightly distorted octahedral coordination geometry, and form a 2D layered supramolecular structureby molecular hydrogen bond and π–π stacking interactions. Complex 2 is made up of four Zn(II)ions, two coordinated OAc− ions, two completely deprotonated (L2)3− moieties and two coordinatedn-propanol molecules, while the Zn(II)ions have slightly distorted trigonal bipyramidal and square pyramidal geometries.

Supplementary Materials

Supplementary File 1

Acknowledgments

This work was supported by the National Natural Science Foundation of China (Grant No. 21361015), which is gratefully acknowledged.

Author Contributions

Wen-Kui Dong and Jing Hao conceived and designed the experiments; Ling-Zhi Liu performed the experiments; Wei-Min Zhou analyzed the data; Gang Li contributed reagents/materials/analysis tools; Wen-Kui Dong wrote the paper.

Conflicts of Interest

The authors declare no competing financial interests.

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Crystals 07 00217 sch001 550
Scheme 1. Syntheses route to H2L1 and H3L2.
Scheme 1. Syntheses route to H2L1 and H3L2.
Crystals 07 00217 sch001
Crystals 07 00217 g001 550
Figure 1. (a) Molecular structure and atom numberings of complex 1 with 30% probability displacement ellipsoids(hydrogen atoms are omitted for clarity); (b) Coordination polyhedron for Co(II) ion of complex 1.
Figure 1. (a) Molecular structure and atom numberings of complex 1 with 30% probability displacement ellipsoids(hydrogen atoms are omitted for clarity); (b) Coordination polyhedron for Co(II) ion of complex 1.
Crystals 07 00217 g001
Crystals 07 00217 g002 550
Figure 2. View of the 2D supramolecular structure of complex 1 showing the O–H···O, O–H···Cl hydrogen bonding and π–π stacking interactions.
Figure 2. View of the 2D supramolecular structure of complex 1 showing the O–H···O, O–H···Cl hydrogen bonding and π–π stacking interactions.
Crystals 07 00217 g002
Crystals 07 00217 g003 550
Figure 3. (a) Molecular structure and atom numberings of complex 2 with 30% probability displacement ellipsoids (hydrogen atoms are omitted for clarity). (b) Coordination polyhedra for Zn1 and Zn2 ions of complex 2.
Figure 3. (a) Molecular structure and atom numberings of complex 2 with 30% probability displacement ellipsoids (hydrogen atoms are omitted for clarity). (b) Coordination polyhedra for Zn1 and Zn2 ions of complex 2.
Crystals 07 00217 g003
Crystals 07 00217 g004 550
Figure 4. Infrared spectra of: (a) H2L1; and (b) H3L2, and their corresponding complexes 1 and 2.
Figure 4. Infrared spectra of: (a) H2L1; and (b) H3L2, and their corresponding complexes 1 and 2.
Crystals 07 00217 g004
Crystals 07 00217 g005 550
Figure 5. UV-vis spectra of: (a) H2L1; and (b) H3L2, and their corresponding complexes 1 and 2.
Figure 5. UV-vis spectra of: (a) H2L1; and (b) H3L2, and their corresponding complexes 1 and 2.
Crystals 07 00217 g005
Table
Table 1. Crystal data and structure refinement parameters for complexes 1 and 2.
Table 1. Crystal data and structure refinement parameters for complexes 1 and 2.
Complex12
FormulaC16H14Br2Cl2CoN2O6C42H46Cl2N4O16Zn4
Formula weight619.941195.21
Temperature (K)293(2)228(1)
Wavelength (Å)0.710730.71073
Crystal systemMonoclinicTriclinic
Space groupP2(1)/cP-1
Unit cell dimensions
a (Å)24.8201(9)9.067(1)
b (Å)10.1475(4)11.72(1)
c (Å)7.8671(3)12.437(1)
α (°)9091.649(9)
β (°)91.459(3)108.56(1)
γ (°)90104.51(1)
V (Å3)1980.8(1)1204.4(2)
Z41
Dc (g cm−3)2.0791.648
μ (mm−1)5.2092.151
F (000)1212.0608.0
Crystal size (mm)0.21 × 0.06 × 0.040.24 × 0.21 × 0.19
θ Range (°)3.36–26.023.43–26.02
Index ranges−30 ≤ h ≤ 2411 ≤ h ≤ 7
−12 ≤ k ≤ 10−14 ≤ k ≤ 13
−9 ≤ l ≤ 8−15 ≤ l ≤ 14
Reflections collected80238045
Independent reflections38914729
Rint0.04120.0414
Completeness to θ = 26.3299.8%99.6%
Data/restraints/parameters3891/0/2644729/4/312
GOF1.0381.044
Final R1, wR2 indices [I > 2σ(I)]0.0480/0.07630.0441/0.0988
R1, wR2 indices (all data)0.0816/0.08900.0664/0.1167
ⓐ111111
Largest differences0.513/−0.5590.412/−0.480
peak and hole (e Å−3)
Table
Table 2. Selected bond distances (Å) and bond angles (°) for complexes 1 and 2.
Table 2. Selected bond distances (Å) and bond angles (°) for complexes 1 and 2.
Complex 1
Co1–O12.083(3)Co1–O62.123(2)
Co1–O42.061(3)Co1–N12.087(4)
Co1–O52.141(2)Co1–N22.123(4)
O4–Co1–O693.3(1)O4–Co1–N1176.4(1)
O4–Co1–N285.5(1)O5–Co1–O6175.3(1)
O5–Co1–N187.6(1)O5–Co1–N287.6(1)
O6–Co1–N187.7(1)O6–Co1–N292.9(1)
N1–Co1–N297.9(1)
Complex 2
Zn1–O11.957(3)Zn1–O52.004(3)
Zn1–O61.977(3)Zn1–N12.122(4)
Zn1–N22.086(4)Zn2–O42.029(3)
Zn2–O52.047(3)Zn2–O71.972(3)
Zn2–O82.037(4)Zn2–O4i2.003(3)
O1–Zn1–O595.8(1)O1–Zn1–O6111.4(2)
O1–Zn1–N188.8(1)O1–Zn1–N2118.6(2)
O5–Zn1–O693.0(1)O5–Zn1–N1172.2(1)
O5–Zn1–N284.5(1)O6–Zn1–N191.1(1)
O6–Zn1–N2130.0(2)N1–Zn1–N287.9(1)
O4–Zn2–O579.3(1)O4–Zn2–O7145.4(1)
O4–Zn2–O8107.9(1)O4–Zn2–O4i77.8(1)
O5–Zn2–O797.1(1)O5–Zn2–O891.5(1)
O5–Zn2–O4i156.1(1)O7–Zn2–O8106.7(2)
O7–Zn2–O4i97.9(1)O8–Zn2–O4i101.9(1)
Symmetry transformations used to generate equivalent atoms: i: 2 − x, 1 − y, −z.
Table
Table 3. Hydrogen bonding interactions (Å, °) for complexes 1 and 2.
Table 3. Hydrogen bonding interactions (Å, °) for complexes 1 and 2.
D–H⋅⋅⋅AD–HH⋅⋅⋅AD⋅⋅⋅AD–H⋅⋅⋅A
1
O5–H5B–O40.862.062.797(4)145
O6–H6A–O10.872.002.746(4)143
O6–H6B–O40.872.072.853(4)151
C8–H8B–O20.972.343.069(5)131
C9–H9A–O60.972.353.272(6)159
C9–H9B–O30.972.543.420(5)150
2
O8–H8–O10.87(4)1.85(5)2.666(5)156(4)
C8–H8B–O60.972.483.308(6)143
Table
Table 4. π–π stacking interactions (Å, °) for complex 1.
Table 4. π–π stacking interactions (Å, °) for complex 1.
Ring 1 Ring 2αDCC(Å)CgI-prep(Å)CgJ-prep(Å)
Cg3 Cg31.7(2)3.999(2)3.734(2)−3.756(2)
Cg4 Cg42.25(19)3.936(2)3.663(2)−3.657(2)
Symmetry codes: Cg3 and Cg4 for complex 1 are the centroids of atoms C1–C6 and C11–C16, respectively; α = dihedral angle between planes I and J; DCC = distance between ring centroids; CgI-perp = perpendicular distance of Cg(I) from ring J; CgJ-perp = perpendicular distance of Cg(J) from ring I.

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Li, G.; Hao, J.; Liu, L.-Z.; Zhou, W.-M.; Dong, W.-K. Syntheses, Crystal Structures and Thermal Behaviors of Two Supramolecular Salamo-Type Cobalt(II) and Zinc(II) Complexes. Crystals 2017, 7, 217. https://doi.org/10.3390/cryst7070217

AMA Style

Li G, Hao J, Liu L-Z, Zhou W-M, Dong W-K. Syntheses, Crystal Structures and Thermal Behaviors of Two Supramolecular Salamo-Type Cobalt(II) and Zinc(II) Complexes. Crystals. 2017; 7(7):217. https://doi.org/10.3390/cryst7070217

Chicago/Turabian Style

Li, Gang, Jing Hao, Ling-Zhi Liu, Wei-Min Zhou, and Wen-Kui Dong. 2017. "Syntheses, Crystal Structures and Thermal Behaviors of Two Supramolecular Salamo-Type Cobalt(II) and Zinc(II) Complexes" Crystals 7, no. 7: 217. https://doi.org/10.3390/cryst7070217

APA Style

Li, G., Hao, J., Liu, L. -Z., Zhou, W. -M., & Dong, W. -K. (2017). Syntheses, Crystal Structures and Thermal Behaviors of Two Supramolecular Salamo-Type Cobalt(II) and Zinc(II) Complexes. Crystals, 7(7), 217. https://doi.org/10.3390/cryst7070217

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