Abstract
1-Benzyl-2-(arylazo)imidazoles, p-RC6H4N=NC3H2-N21-CH2Ph [RaaiBz (2); R=H(a), Me(b), Cl(c)], react with K2PtCl4 in boiling MeCN–H2O (1:1 v/v) to give brownish-red Pt(RaaiBz)Cl2 (3) complexes. Addition of dioxolene in the presence of Et3N to a CHCl3–MeOH solution of Pt(RaaiBz)Cl2 yields green mixed complexes of composition [Pt(RaaiBz)(O,O)] [O,O = catecholate (cat) (4); 4-tert-butylcatecholate (tbcat), (5); 3,5-di-tert-butylcatecholate (dtbcat), (6); tetracholorocatecholate (tccat), (7)] which were characterised by elemental analyses, i.r., u.v.–vis.–near i.r. and 1H-n.m.r. spectral data. The solution electronic spectra exhibit ligand-to-ligand charge-transfer (l.l.c.t) transitions in the red to near i.r. region; the position and symmetry of the band depend upon the substituent on the dioxolene and arylazoimidazole. This effect is qualitatively assigned as HOMO(dioxolene) → LUMO(RaaiBz). A cyclic voltammogram of the dioxolene complex reveals two consecutive oxidative couples corresponding to catechols to semiquinones and semiquinone to quinone, respectively and the reductive couples represent azo reductions.
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Rauth, G.K., Pal, S., Das, D. et al. Synthesis, spectral characterisation and electrochemical studies of dichloro-{1-benzyl-2-(arylazo)imidazole}platinum(II) complexes and their dioxolene derivatives. Transition Metal Chemistry 26, 679–684 (2001). https://doi.org/10.1023/A:1012035714276
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DOI: https://doi.org/10.1023/A:1012035714276