Synthesis,electrochemical and e.p.r. spectral studies of binuclear copper(II) complexes with new pentadentate L-proline-based binucleating ligands |
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| Authors: | Sougandi Ilango Mahalakshmi Rajaram Kannappan Ramu Rajendiran Thekkelnayackanpatti M Venkatesan Rangarajan Sambasiva Rao Pillutla |
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| Institution: | (1) Department of Chemistry, Pondicherry University, R.V. Nagar, Kalapet, Pondicherry, 605 014, India |
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| Abstract: | The synthesis, reduction, optical and e.p.r. spectral properties of a series of new binuclear copper(II) complexes, containing bridging moieties (OH–, MeCO2
–, NO2
–, and N3
–), with new proline-based binuclear pentadentate Mannich base ligands is described. The ligands are: 2,6-bis(prolin-1-yl)methyl]4-bromophenol H3L1], 2,6-bis(prolin-1-yl)methyl]4-t-butylphenol H3L2] and 2,6-bis(prolin-1-yl)methyl]4-methoxyphenol H3L3]. The exogenous bridging complexes thus prepared were hydroxo: Cu2L1(OH)(H2O)2] · H2O (1a), Cu2L2(OH)(H2O)2] · H2O (1b), Cu2L3(OH)(H2O)2] · H2O (1c), acetato Cu2L1(OAc)] · H2O (2a), Cu2L2(OAc)] · H2O (2b), Cu2L3(OAc)] · H2O (2c), nitrito Cu2L1(NO2)(H2O)2] · H2O (3a), Cu2L2(NO2)(H2O)2] · H2O (3b), Cu2L3(NO2)(H2O)2] · H2O (3c) and azido Cu2L1(N3)(H2O)2] · H2O (4a), Cu2L2(N3)(H2O)2] · H2O (4b) and Cu2L3(N3)(H2O)2] · H2O (4c). The complexes were characterized by elemental analysis and by spectroscopy. They exhibit resolved copper hyperfine e.p.r. spectra at room temperature, indicating the presence of weak antiferromagnetic coupling between the copper atoms. The strength of the antiferromagnetic coupling lies in the order: NO2  N3  OH OAc. Cyclic voltammetry revealed the presence of two redox couples CuIICuII  CuIICuI CuICuI. The conproportionality constant K
con for the mixed valent CuIICuI species for all the complexes have been determined electrochemically. |
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