Synthesis, structure, redox and spectra of green iridium complexes of tridentate azo-aromatic ligands |
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Authors: | Manashi Panda Chayan Das Chen-Hsiung Hung and Sreebrata Goswami |
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Institution: | (1) Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, 700 032, India;(2) Institute of Chemistry, Academia Sinica, Nankong, Taipei 115, Taiwan |
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Abstract: | Reactions of IrCl3·xH2O with the ligands, 2-(phenylamino)phenylazo]pyridine (HL1a) and 2-(p-tolylamino)phenylazo]pyridine (HL1b) produce Ir(L1)2]Cl (L1 = L1a, 1]Cl and L1 = L1b, 2]Cl) along with many unidentified products. The iridium complexes have been characterized by various techniques such as X-ray
crystallography, mass spectrometry, 1H and 13C NMR, cyclic voltammetry and absorption studies. The complex 1]ClO4 crystallises in triclinic space group. The crystallographic data have been determined. Notably, the Ir-N (azo) lengths are
short (av. 1·9875(4) ?) as compared to the remaining four Ir-N lengths (av. 2·052(5) ?). There is significant degree of ligand
backbone conjugation in the coordinated ligands, which result in shortening of the C-N lengths on the other side of the middle
phenyl ring and also in lengthening of the diazo (N=N) lengths. The complexes display multiple low energy transitions ranging
between 1010 and 450 nm. These are electro active and show three reversible redox responses in the potential range, +1·5 V
to −1·5 V. The cathodic potential responses are ascribed as ligand reductions, while the redox process at the anodic potential
occurs at a mixed metal-ligand (HOMO) orbital. |
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Keywords: | Iridium complexes azo-aromatic ligands synthesis X-ray structure redox and spectral properties |
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