Copper(II) complexes of sterically hindered schiff base ligands: synthesis, structure, spectra and electrochemistry

Balamurugan, Ramalingam ; Palaniandavar, Mallayan ; Halcrow, Malcolm A. (2006) Copper(II) complexes of sterically hindered schiff base ligands: synthesis, structure, spectra and electrochemistry Polyhedron, 25 (5). pp. 1077-1088. ISSN 0277-5387

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S02775...

Related URL: http://dx.doi.org/10.1016/j.poly.2005.07.047

Abstract

The synthesis, structure and spectral and redox behaviour of copper(II) complexes of sterically constrained N3, N3S2 and N2S2 ligands are described. The ligands 2,6-bis(2,4,6-trimethylphenyliminomethyl)pyridine (L1), 2,6-bis(2,6-diisopropylphenyliminomethyl)pyridine (L2), 2,6-bis(2-methylthiophenyliminomethyl)pyridine (L3), 1,3-bis(2-methylthiophenyliminomethyl)benzene (L4), 1,3-bis(2,4,6-trimethylphenyliminomethyl)benzene (L5) and 1,3-bis(2,6-diisopropyl-phenyliminomethyl)benzene (L6) have been synthesized. The 1:1 copper(II) complexes of L1-L5 have been isolated and characterized by spectral and electrochemical techniques. The X-ray crystal structure of the complex [Cu(L2)Cl2] (2) has been successfully determined and is found to possess a distorted square pyramidal coordination geometry. The replacement of isopropyl groups in this complex by the less sterically demanding methyl groups as in [Cu(L1)Cl2] leads to a decreased geometric distortion. The complexes show relatively high positive redox potentials with a low reorganizational energy barrier for electron transfer involving the Cu(II)/Cu(I) couple. The redox cycle of the complexes 1 and 2 has been explained by assuming a square scheme. The spectral and electrochemical properties of CuN3S2 and CuN2S2 complexes generated by the incorporation of thioether sulfurs into L1/L2 and L4/L5, respectively, are also discussed. Both the complexes show positive redox potentials suggesting the coordination of at least one thioether sulfur to copper(II). The incorporation of a pyridine nitrogen donor into the CuN2S2 complexes leads to higher LF field strengths but with lower absorptivities. The coordination of Cl- ions to the CuN3S2 and CuN2S2 complexes significantly alter the spectral and redox properties of the complexes.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Copper(II) Complexes; X-ray Structure; Tri- and Pentadentate Ligands; EPR Spectra; Redox Properties
ID Code:30917
Deposited On:27 Dec 2010 07:00
Last Modified:05 Mar 2011 05:43

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