Nickel(II) and copper(II) complexes of Schiff base ligands containing N4O2 and N4S2 donors with pyrrole terminal binding groups: Synthesis, characterization, X-ray structures, DFT and electrochemical studies |
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Authors: | Ali Akbar Khandar Christine Cardin John McGrady Seyed Amir Zarei |
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Institution: | a Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 51666-14766, Iran b Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK c Department of Chemistry, University of Oxford, OX1 3QR, UK |
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Abstract: | A series of hexadentate ligands, H2Lm (m = 1−4), 1H-pyrrol-2-ylmethylene]{2-2-(2-{1H-pyrrol-2-ylmethylene]amino}phenoxy)ethoxy]phenyl}amine (H2L1), 1H-pyrrol-2-ylmethylene]{2-4-(2-{1H-pyrrol-2-ylmethylene]amino}phenoxy)butoxy]phenyl}amine (H2L2), 1H-pyrrol-2-ylmethylene]2-({2-(2-{1H-pyrrol-2-ylmethylene]amino}phenyl)thio]ethyl}thio)phenyl]amine (H2L3) and 1H-pyrrol-2-ylmethylene]2-({4-(2-{1H-pyrrol-2-lmethylene]amino}phenyl)thio]butyl}thio) phenyl]amine (H2L4) were prepared by condensation reaction of pyrrol-2-carboxaldehyde with {2-2-(2-aminophenoxy)ethoxy]phenyl}amine, {2-4-(2-aminophenoxy)butoxy]phenyl}amine, 2-({2-(2-aminophenyl)thio]ethyl}thio)phenyl]amine and 2-({4-(2-aminophenyl)thio]butyl}thio)phenyl]amine respectively. Reaction of these ligands with nickel(II) and copper(II) acetate gave complexes of the form MLm (m = 1−4), and the synthesized ligands and their complexes have been characterized by a variety of physico-chemical techniques. The solid and solution states investigations show that the complexes are neutral. The molecular structures of NiL3 and CuL2, which have been determined by single crystal X-ray diffraction, indicate that the NiL3 complex has a distorted octahedral coordination environment around the metal while the CuL2 complex has a seesaw coordination geometry. DFT calculations were used to analyse the electronic structure and simulation of the electronic absorption spectrum of the CuL2 complex using TDDFT gives results that are consistent with the measured spectroscopic behavior of the complex. Cyclic voltammetry indicates that all copper complexes are electrochemically inactive but the nickel complexes with softer thioethers are more easily oxidized than their oxygen analogs. |
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Keywords: | Copper(II) complexes Nickel(II) complexes X-ray structure Pyrrol-2-carboxaldehyde Cyclic voltammetry DFT calculations |
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