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Article

Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}

1
Department of Chemistry, School of Science, Azzahra University, P.O.Box 1993891176, Tehran, Iran
2
Institute and Outpatient Clinic for Occupation and Social Medicine of the Justus-Liebig-University of Giessen, Aulweg 129 III, 35392 Giessen, Federal Republic of Germany
*
Author to whom correspondence should be addressed.
Molecules 2007, 12(7), 1410-1419; https://doi.org/10.3390/12071410
Submission received: 6 June 2007 / Revised: 9 July 2007 / Accepted: 10 July 2007 / Published: 12 July 2007

Abstract

:
A novel, mixed-valent copper(I)-copper(II) complex, {[bis(ethylene-diamine)copper(II)] bis[diiodocuprate(I)]} (1), has been prepared by electrochemical dissolution of a sacrificial copper anode in a solution of ethylenediamine (en), I2 and tetraethylammoniumperchlorate (TEAP) as supporting electrolyte in acetonitrile (AcN) and characterized by single-crystal X-ray structure determination. The crystal structure of the complex 1 shows that it consists of a CuI2 polymer formed from I-  ligands bridging Cu(I) ions, with a nearly square planar geometry of bivalente Cu(II) atoms chelated by two ethylenediamine ligands. The results also show that direct electrosynthesis of the complex had high current efficiency, purity and electrolysis yield.

Introduction

The design of complex molecular architectures based on transition metal atoms and organic ligands is an important goal for synthetic chemistry as it provides the opportunity to control or encode the properties of a material at the molecular level [1]. Suitable organic ligands favoring structure-specific self-assembly are the bases for the construction of coordination architectures. On the other hand, copper halides have been successfully used for the synthesis of uncharged coordination polymer arrays [2,3,4]. Various factors, such as the stiochiometric metal-to-ligand ratio, the halide and the nature and substitution of the ligand have been shown to influence the form of the copper-halide motifs and the structures of the resulting coordination polymer [2,3]. Recently, increasing attention has been paid to the use of flexible bridging units in the construction of supramolecular architectures [5,6] and this approach is attractive because the flexibility and conformation freedoms of such ligands offer the possibility for the construction of unprecedented frameworks with tailored properties and functions [7].
Although to date remarkable Cu(I) complexes [8,9,10,11] and examples of Cu(I) complexes with halocuprate anion [12,13,14] have been reported, there is no report on diiodocuprate (I) anion polymeric complex with ethylenediamine. Thus, we report herein the electrosynthesis and crystal structure of a novel Cu(I) polymeric complex with potentiostatic dissolution of copper anode in a solution of ethylendiamine and iodine in AcN.

Results and Discussion

Electrosynthesis

Direct anodic dissolution of copper metal and cathodic reduction of iodine in AcN proved to be a simple and efficient one-step route to new copper(I) iodide ligand polymeric complex, {[Cu(en)2][CuI2]2}n (1) in an undivided cell. The dark brown air-stable crystalline complex is obtained by dissolving in DMF. The complex is insoluble in water and most common organic solvents except DMF. The electrochemical cell for this system could be presented as follows:
Cu / en + CH3CN + TBAP+ I2 / Pt
The electron transfer reaction mechanism involves the anodic oxidation of copper to Cu+, which in the presence of I- (resulting from the reduction of I2 at the cathode) forms the CuI2- complex. However, since en is a stronger ligand than I-, some of Cu+ participates in a disproportionation reaction to form Cu+2 as Cu (en)2.
Cathode:½ I2 +e → I
Anode:Cu → Cu+ + e
2Cu+ → Cu2+ + Cu
Cu+ + 2I- → CuI2
Cu+2 + 2en + 2 CuI2 → [Cu(en)2][ CuI2]2

Electrochemistry

A sweep for complex from +0.4 to +1.2 V shows only one quasi-reversible anodic peak (EA1= 0.98 V) and the backwards cathodic sweep (+1.2 to 0.0 V) shows two cathodic peaks at EC1= 0.74 V and EC2= 0.09 V (Figure 1). In a second reversing anodic sweep another anodic peak (EA2= 0.61 V) corresponding to the reoxidation of the product of cathodic peak at EC2= 0.09 V appeared. If the studied range is limited from +1.2 to +0.6 V (Figure 1, inset, right) a quasi-reversible wave at EC1= 0.74 V and EA1= 0.98 V was observed and assigned to the Cu(II)/Cu(I) redox couple, while a potential sweep in the limited range of +0.8 to 0.0 V shows the second redox couple (EC2= 0.09 V, EA2= 0.61 V) corresponding to Cu(I)/Cu(0). The latter redox assignment is further supported by recording the cyclic voltammogram of CuI under the same experimental conditions. As it can be seen from Figure 1 (inset, left) the Cu(I) in CuI cyclic voltammogram is reduced to Cu(0) at EC2= 0.09 V and its anodic compartment wave is observed at EA2= 0.61 V, which is a good indication of the presence of a Cu(I)/Cu(0) redox couple in the complex.
Since the cyclic voltammogram of ethylenediamine didn’t show any wave in the potential range of 0.0 to 1.2 V (data not shown), thus the redox couples in the complex have been assigned to the metal center in the complex. Therefore, the observed cyclic voltammogram was consistent and characteristic of two Cu (II)/Cu (I) and Cu (I)/Cu (0) redox couples in the structure of the complex.
Figure 1. Cyclic voltammogram of 1 at the glassy carbon electrode in DMF. Initial anodic scan from 0.6 V to 1.2 V and reversing scan up to 0.0 V. Inset right: cyclic voltammogram of 1 in the 1.2 V to 0.6 V range. Inset left: cyclic voltammogram of CuI in the 0.8 V to 0.0 V range. Scan rate 50 mVs-1.
Figure 1. Cyclic voltammogram of 1 at the glassy carbon electrode in DMF. Initial anodic scan from 0.6 V to 1.2 V and reversing scan up to 0.0 V. Inset right: cyclic voltammogram of 1 in the 1.2 V to 0.6 V range. Inset left: cyclic voltammogram of CuI in the 0.8 V to 0.0 V range. Scan rate 50 mVs-1.
Molecules 12 01410 g001

Structural studies

The crystallographic data are summarized in Table 1 and selected bond distances and angles are given in Table 2. Views of the [Cu (en)2][CuI2]2 complex 1 shown in Figure 2 and Figure 3 reveal that it crystallized in the monoclinic crystal system with space group C2/m. Complex 1 is mixed-valence. The asymmetric unit of 1 contains two crystallographically independent metal centers in the crystal structure. The bivalent Cu (1) atom has a nearly square planar geometry and was chelated by two ethylenediamine ligands. The two inter and intraligand N–Cu–N angles differ only slightly from 90° (85.51(27)°–94.49(27)°), and the two N–Cu–N angles are close to 180°. The Cu–N distance 2.003(10)Å is similar to those found in other Cu(II) complexes [15,16,17]. The structure of 1 consisted of a chain of alternatively perpendicular planes Cu4I4 running along the c axis of CuI2- formed from I- ligands bridging Cu (I) ions. The monovalent Cu(2) atom ion in this complex is distorted tetrahedral. The I1i—Cu2—I1 angle is much less than 109.5°, being only 96.72(0)°. On the contrary, the I2—Cu2—I1 angle (112.25(0)°,) is much larger than those of a tetrahedral complex. The average Cu–I bond distance (2.6752 Å) is similar to that found in other Cu (I) (diimine) pseudotetrahedral complexes [18,19,20]. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters are reported in Table 3.
Figure 2. ORTEP view of the crystal structure of [Cu(C)2]+, showing the atom labeling scheme. The thermal ellipsoids enclose 50% of the electronic density.
Figure 2. ORTEP view of the crystal structure of [Cu(C)2]+, showing the atom labeling scheme. The thermal ellipsoids enclose 50% of the electronic density.
Molecules 12 01410 g002
Figure 3. A view of the overall network slightly offset from directly down the c axis.
Figure 3. A view of the overall network slightly offset from directly down the c axis.
Molecules 12 01410 g003
Table 1. Crystal data and structure refinement for 1.
Table 1. Crystal data and structure refinement for 1.
1
T/K293(2)
Crystal SystemMonoclinic
Space groupC 2/m
a10.3632(11)
b/Å13.2843(13)
c/Å6.5115(7)
β/o117.339(11)
V3796.30(16)
Z, Dcalc./Mg.m-32, 3.346
μ/mm-111.700
F(000)702.0
Crystal size/mm3
θ/o2.69 to 28.050
h/k/l-12,13/-17,17/-8, 8
Refl. unique996
Refl. Observed [I>2σ(I)]915
R(int)0.040
Data /restraints/parameters996/ 0 /40
Goodness-of-fit on F21.280
Final R indices [I>2σ(I)]R1 =0.0614, wR2 = 0.1632
R indices for all dataR1 = 0.0649, wR2 = 0.1661
Largest difference Peak and hole (e. Å–3)0.799 and -0.740
[*] R1 = Σ ||Fo|-|Fc|| / Σ|Fo|, wR2 = {Σ[w(Fo2-Fc2)2] / Σ[w(Fo2)2]}½
Table 2. Selected geometric parameters (Å, °) for 1.
Table 2. Selected geometric parameters (Å, °) for 1.
I1—Cu2i2.696(1)Cu1—N1iv2.003(10)
I1—Cu22.696(1)Cu1—N12.003(10)
I2—Cu22.642(24)Cu1—N1iii2.003(10)
I2—Cu2ii2.671(3)Cu1—N1v2.003(10)
Cu2—I2ii2.671(3)N1—C11.477(11)
Cu2—Cu2ii2.930(2)C1—C1v1.506(16)
 
Cu2i—I1—Cu283.28(0)N1iii—Cu1—N1179.99(27)
Cu2—I2—Cu2ii66.93(5)N1iii—Cu1—N1iv85.51(27)
I2—Cu2—I1112.25(0)N1—Cu1—N1iv94.49(27)
I2ii—Cu2—I1110.73(0)N1iii—Cu1—N1v94.49(27)
I1i—Cu2—I196.72(0)N1—Cu1—N1v85.51(27)
I2—Cu2—Cu2ii57.01(4)N1iv—Cu1—N1v179.99(27)
I2ii—Cu2—Cu2ii56.06(4)C1—N1—Cu1107.34(49)
I1i—Cu2—Cu2ii131.61(0)N1—C1—C1v107.20(69)
I2—Cu2—I2ii113.07(6)
Symmetry codes:
(i) -x, 1-y, 1-z; (ii) -x, 1-y, -z; (iii) -1-x, 1-y, -z; (iv) x, 1-y, z;
(v) -1-x, y, -z.
Table 3. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)
Table 3. Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)
xyzUiso*/Ueq
I10.00000.34835 (5)0.50000.0159 (3)
I2−0.24076 (7)0.5000−0.17764 (10)0.0145 (3)
Cu1−0.50000.50000.00000.0127 (4)
Cu2−0.00269 (160.50000.2230 (2)0.0227 (4)
N1−0.3879 (8)0.6107 (5)0.2179 (11)0.0174 (13)
C1−0.4199 (10)0.7046 (6)0.0819 (15)0.0208 (16)

Conclusions

The utility of direct and uncomplicated electrosynthesis to obtain this type of copper complex of ethylenediamine with high yield and high purity has been demonstrated. Comparing with the usual chemically copper complexes of ethylenediamine prepared over the years [21], the resulting complex is a new and unusual member of an interesting class of mixed-valence one-dimensional supramolecular copper complexes.

Experimental

Apparatus

Electrochemical experiments were performed using a Metrohm model 746 VA trace analyzer connected a 747 VA stand. A glassy carbon electrode (0.2 mm diameter) was used as the working electrode. A platinum wire and a commercial KCl saturated Ag/AgCl electrode from Metrohm were used as the auxiliary and reference electrodes, respectively. The solutions were purged with 99.999% argon for 10 min before the start of the experiments. Electrosynthesis was performed using a Zahner electrik PP200 potentiostat/galvanostat. The electrochemical cell consists of a tall-form beaker (100 mL) with three cross sectional openings. The potential of copper anode was held 0.5 V with respect to an Ag/AgCl reference electrode and a platinum sheet was used as a cathode counter electrode. A magnet stirring system was also used.

Reagents

Acetonitrile (AcN, Merck), ethylenediamine (en, Merck), iodine (Merck), dimethylformamide (DMF, Merck) and tetrabutylammonium perchlorate (TBAP, Fluka) as supporting electrolyte were used as received.

Characterization of the Complex [22]

Diffraction data for 1 were collected on a STOE-IPDSII diffractometer using graphite-monochromated Mo-Ka radiation (¼0.71073Å). Data were collected and integrated using the stoe X-AREA software package [23]. A numerical absorption correction was applied using X-RED and X-SHAPE software [24]. The structure was 100 solved by direct methods (SHELXS-97 [25]). The structure refinement was performed by a full-matrix least-squares method against F2 (SHELXL-97 [25]). All non-H-atoms were refined anisotropically, all H-atoms were inserted in the calculated positions.

Electrosynthesis

Electrosynthesis was carried out in an undivided cell. The copper anode and platinum cathode were inserted in a solution of ethylenediamine (0.030 g, 0.5 mmol), iodine (0.126 g, 0.5 mmol) and 0.10 M TBAP as supporting electrolyte in can (50 mL). Potentiostatic oxidation of the copper anode at 0.5 V resulting in colorless solution initially. Electrolysis was stopped after 30 minutes and brown product was filtered off, washed with AcN and dried. The final brown precipitate was dissolved in DMF and allowed to stand over several days to deposit the complex as dark brown prisms suitable for X-ray crystallography. The IR spectra of both, brown precipitate and its crystalline complex showed the same bands, indicating that DMF did not engaged in the resulted crystalline complex.

Microanalysis

Found: C, 5.86; H, 1.95; N, 6.84. C4H16Cu3I4N4 required C, 5.87; H, 1.97; N, 6.85 %; Crystal data: C4H16Cu3I4N4, 802.30, monoclinic, space group C2/m, a=10.3632(11), b=13.2843(13), c=6.5115(7) Å, β=117.339(11), U = 2713 Å3, Z = 2, µ(Mo-Ka) = 3.346 cm-1, T = 293(2) K, N = 996, No [[I>2σ(I)]] = 915; R = 0.0614, Rw = 0.1632.

Acknowledgments

The authors express their gratitude for financial support from Azzahra University Research Council.

References and Notes

  1. Hannon, M. J.; Painting, C. L.; Plummer, E. A.; Childs, L. J.; Alcock, N. W. Competing Supramolecular Interactions Give a New Twist to Terpyridyl Chemistry: Anion- and Solvent-Induced Formation of Spiral Arrays in Silver (I) Complexes of a Simple Terpyridine. Chem. Eur. J. 2002, 8, 2226–2238. [Google Scholar] [CrossRef]
  2. Nather, C.; Jess, I. Synthesis, Crystal Structure and Thermal Reactivity of New Copper (I) Halide Pyrimidine-Containing Coordination Polymers. Eur. J. Inorg. Chem. 2004, 14, 2868–2876. [Google Scholar]
  3. Graham, P. M.; Pike, R. D.; Sabat, M.; Bailey, R. D.; Pennington, W. T. Coordination Polymers of Copper (I) Halides. Inorg. Chem. 2000, 39, 5121–5132. [Google Scholar] [CrossRef] [PubMed]
  4. Blake, A. J.; Brooks, N. R.; Champness, N. R.; Hanton, L. R.; Hubberstey, P.; Schroder, M. Copper (I) Halide Supramolecular Networks Linked by N-Heterocyclic Donor Bridging Ligands. Pure Appl. Chem. 1998, 70, 2351–2357. [Google Scholar] [CrossRef]
  5. Zheng, Y.; Du, M.; Li, J. R.; Zhang, R. H.; Bu, X. H. Tuning the Framework Formation of Silver(I) Coordination Architectures with Heterocyclic Thioethers. Dalton Trans. 2003, 8, 1509–1514. [Google Scholar]
  6. Long, L. S.; Cai, J. W.; Ren, Y. P.; Tong, Y. X.; Chen, X. M.; Ji, L. N.; Huang, R. B.; Zheng, L. S. Hydrogen Bond Induced Change of Geometry and Crystallized Form of Copper(II)Complexes: Syntheses and Crystal Structure of Complexes with Schiff-Base Ligands Containing Two Imidazolyl Groups. J. Chem. Soc. Dalton Trans. 2001, 6, 845–849. [Google Scholar] [CrossRef]
  7. Su, C. Y.; Cai, Y. P.; Chen, C. L.; Smith, M. D.; Kaim, W.; Zoye, H. C. Z. Ligand-Directed Molecular Architectures: Self-Assembly of Two-Dimensional Rectangular Metallacycles and Three-Dimensional Trigonal or Tetragonal Prisms. J. Am. Chem. Soc. 2003, 125, 8595–8613. [Google Scholar]
  8. Battaglia, L. P.; Corradi, A. B.; Menabue, L. Structure Magnetism Correlation in Dimeric Copper (II) Carboxylates-Crystal and Molecular-Structure of Tetra-Mu-(Propanoato-O,O’)-bis[aquacopper (II)]. J. Chem. Soc. Dalton Trans. 1986, 1653–1657. [Google Scholar] [CrossRef]
  9. Harcourt, R. D.; Skrezenek, F. L.; Maclagan, R. Nonempirical Valence Bond Studies of the Origin of the Antiferromagnetism of Copper (II) Carboxylate Dimers. J. Am. Chem. Soc. 1986, 108, 5403–5408. [Google Scholar] [CrossRef]
  10. Gonzalez-Alvarez, M.; Alzuet, G.; Borras, J.; Macias, B.; Castineiras, A. Oxidative Cleavage of DNA by a New Ferromagnetic Linear Trinuclear Copper (II) Complex in the Presence of H2O2/Sodium Ascorbate. Inorg. Chem. 2003, 42, 2992–2998. [Google Scholar]
  11. Chung, Y. H.; Wei, H. H.; Liu, Y. H.; Lee, G. H.; Wang, Y. Reinvestigation of the Crystal Structure and Cryomagnetic Behaviour of Copper (II) Propionates. Polyhedron 1998, 17, 449–455. [Google Scholar] [CrossRef]
  12. Mirkhani, V.; Harkema, S.; Kia, R. Bis[N,N '-bis(diphenylmethylene)ethylenediamine-kappa N-2,N ']copper(I) Dichlorocuprate(I). Acta Cryst. C 2004, 60, m343–344. [Google Scholar] [CrossRef]
  13. Goreshnik, E.; Schollmeyer, D.; Mys’kiv, M. Bis(2-methylbenzimidazole-kappa N-1)copper(I)Dichlorocuprate (I). Acta Cryst. E 2004, 60, m279–281. [Google Scholar] [CrossRef]
  14. Su, C. Y.; Kang, B. S.; Sun, J. Synthesis and Crystal Structure of the Tetranuclear Copper(I) Complex [Cu4I4(MPTQ)(2)] with a N,S,N'-Tridentate Ligand (MPTQ=8-((2-pyridylmethyl)thio)-quinoline). Chem. Lett. 1997, 8, 821–822. [Google Scholar]
  15. Xu, Y. Q.; Luo, J. H.; Yuan, D. Q.; Xu, Y.; Cao, R.; Hong, M. C. [Cu(dca)(2)(en)](n): A Two-Dimensional Copper (II) Coordination Polymer with Both Mu (1,5)-dca and Pseudo-mu(1,3)-dca Bridges. J. Mol. Struct. 2003, 658, 223–228. [Google Scholar]
  16. Cavicchioli, M.; Massabni, A. C.; Ferreira, A. M. D.; Castellano, E. E.; Crespi, M. S. Synthesis, Structure and Redox Properties of an Unexpected Trinuclear Copper(II) Complex with Aspartame: [Cu(apm)(2)Cu(mu-N,O : O '-apm)(2)(H2O)Cu(apm)(2)(H2O)]center Dot 5H(2)O. Inorg. Chem. Acta 2005, 358, 4431–4436. [Google Scholar] [CrossRef]
  17. Beloso, I.; Borras, J.; Castro, J.; Garcia-Vazquez, J. A.; Perez-Lourido, P.; Romero, J.; Sousa, A. Flexidentate Behaviour of 2-Pyridylsulfonamides - Direct Electrochemical Synthesis and Spectroscopic and X-Ray Characterization of Neutral Copper (II) Complexes of N-(2-Pyridyl) Sulfonamides. Eur. J. Inorg. Chem. 2004, 3, 635–645. [Google Scholar] [CrossRef]
  18. Hanton, L.R.; Hellyer, R. M.; Spicer, M. D. Structural Variations in Copper(I) Iodide Coordination Polymers of Sulfide and Disulfide Containing Flexible 3-Substituted Pyridine Ligands. Inorg. Chem. Acta 2006, 359, 3659–3665. [Google Scholar]
  19. Goher, M. A. S.; Hafez, A. K.; Mak, T. C. W. A Copper(I) Complex Containing a New Structure of the [Cu2I3](-) Anion. Reaction of CuI with Quinaldic Acid and the Crystal Structure of Tris-(2-carboxyquinoline) triiododicopper(I) Monohydrate. Polyhedron 2001, 20, 2583–2587. [Google Scholar]
  20. Feng, H.; Zhou, X. P.; Wu, T.; Li, D.; Yin, Y. G.; Ng, S. W. Hydrothermal Synthesis of Copper Complexes of 4 '-Pyridyl Terpyridine: From Discrete Monomer to Zigzag Chain olymer. Inorg. Chem. Acta 2006, 359, 4027–4035. [Google Scholar] [CrossRef]
  21. Romano, V.; Pizzino, T.; Gianguzza, A.; Maggio, F. Studies on Complex-Formation of Bis-(ethylenediamine)-copper (II) with Chloride, Bromide, Iodide, and Azide Ions. Inorg. Nucl. Chem. Lett. 1975, 11, 177–183. [Google Scholar] [CrossRef]
  22. CCDC No: 637522 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif."
  23. Stoe & Cie. X–RED, version 1.28b, Program for Data Reduction and Absorption Correction; Stoe & Cie GmbH: Darmatadt, Germany, 2005. [Google Scholar]
  24. Stoe & Cie. X–SHAPE, vesion 2.05: Program for Crystal Optimization for Numerical Absorption Correction; Stoe & Cie GmbH: Darmatadt, Germany, 2004. [Google Scholar]
  25. Sheldrick, G. M. SHELX97. Program for Crystal Structure Solution and Refinement; University of Göttingen: Göttingen, Germany, 1997. [Google Scholar]
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MDPI and ACS Style

Fotouhi, L.; Dehghanpour, S.; Heravi, M.M.; Ardakani, M.D. Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}. Molecules 2007, 12, 1410-1419. https://doi.org/10.3390/12071410

AMA Style

Fotouhi L, Dehghanpour S, Heravi MM, Ardakani MD. Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}. Molecules. 2007; 12(7):1410-1419. https://doi.org/10.3390/12071410

Chicago/Turabian Style

Fotouhi, Lida, Saeed Dehghanpour, Majid M Heravi, and Mahboobeh Dashti Ardakani. 2007. "Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}" Molecules 12, no. 7: 1410-1419. https://doi.org/10.3390/12071410

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