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Reaction of Ni(ClO4)2 · 6H2O with 1-alkyl-2-(arylazo)imidazole (RaaiR/) and sodium azide (NaN3) or ammonium thiocyanate (NH4SCN) (1 : 2 : 2 molar ratio) in methanol gives [Ni(RaaiR/)2(X)2] (X=N3 (3, 4) and SCN (5, 6). All these complexes are characterized by elemental analyses, UV-Vis and IR spectral data, thermal and magnetic moment measurements. The X-ray structure is confirmed by single crystal measurement of [Ni(Pai-Me)2(N3)2] (3a). Cyclic voltammetry exhibits quasireversible response at >0.80 V corresponding to Ni(III)/Ni(II) couple along with ligand reductions at negative potential (<-0.5 V) to SCE reference. The electronic structure, spectral and redox properties are explained by DFT (Gaussian03) calculation. [ABSTRACT FROM AUTHOR]

The reaction of [Ru(OH2)2 (RaaiR')]2+ [RaaiR' = 1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N = N-C3H2-NN(1)-R', R = H (1), Me (2), Cl (3); R' = Me (a), Et (b), CH2Ph (c)] with 8-quinolinol (HQ) in acetone solution followed by the addition of NH4PF6 afforded violet, mixed ligand complexes of composition [Ru(Q)(RaaiR')2](PF6). The structure of [Ru(Q)(MeaaiMe)2](PF6) (2a) has been confirmed by X-ray diffraction studies.Solution electronic spectra exhibit a strong MLCT band at 560-580 nm in MeCN. Cyclic voltammogrames show a Ru(III)/Ru(II)couple at 1.0-1.1 V versus SCE along with three successive ligand reductions. The electronic properties are correlated with EHMO results. [ABSTRACT FROM AUTHOR]

1-Alkyl-2-(naphthyl-(α/β)-azo)imidazoles (α/β-NaiR; R = Me, Et and CH 2 Ph) react with (NH 4 ) 2 [OsCl 6 ] and complexes OsCl 2 (NaiR) 2 are isolated in two isomeric forms: blue-violet ( 3 , 4 ) and red-violet ( 5 , 6 ). The ligand is a bidentate N (N(imidazole)), N′ (N(azo)) donor type. With reference to the pairs of Cl, Cl; N, N and N′, N′ atoms the blue-violet and red-violet isomers are assigned to cis - trans - cis ( ctc ) and cis - cis - cis ( ccc ) configurations respectively. IR spectra of the complexes show two v (Os-Cl) bands and support the cis -OsCl 2 configuration. 1 H NMR spectra also support the ctc and ccc -configuration. The structure of the blue-violet complex OsCl 2 (α-NaiEt) 2 has been determined by X-ray crystallography and the ctc configuration has been confirmed. The structure shows an unusually long N=N bond length, 1.331(4) Å, which is elongated by 0.07 Å compared to the free ligand value. [ABSTRACT FROM AUTHOR]

1-Alkyl-2-(arylazo)imidazoles ( p -R-C 6 H 4 -N=N-C 3 H 2 N 2 X, abbreviated as RaaiX, R = H( a ), CH 3 ( b ), Cl( c ); X = N(1)-CH 3 ( 1 ), N(1)-CH 2 -C 6 H 5 ( 2 )) have been reacted with (NH 4 ) 2 [OsCl 6 ] and OsCl 2 (RaaiX) 2 species isolated in two isomeric forms, blue-violet ( 3 , 5 ) and red-violet ( 4 , 6 ). IR spectra show two ν(Os-Cl) modes and support a cis -OsCl 2 configuration. X-ray diffraction methods were used to determine structures of blue-violet isomers. In terms of the three coordination pairs around Os(II), Cl, Cl, N, N (N(imidazole), N) and N′, N′ (N(azo), N′) the blue-violet isomers have a cis-trans-cis ( ctc ) configuration. 1 H NMR data for the red-violet complexes (isomers B) and results concerning analogous ruthenium(II) complexes indicate isomer B to have cis-cis-cis ( ccc ) configuration. Absorption spectra show an intense MLCT band at ca 580 nm along with two weak bands at 800 and 1000 nm. Cyclic voltammetry shows quasi -reversible Os(III)/Os(II) and Os(IV)/Os(III) couples at 0.4-0.6 V and 1.3-1.5 V versus SCE and ill-defined azo reductions. The X-Ray structures show unusually long N=N bond lengths, 1.31-1.32 Â, elongated by some 0.06 Â compared to the free ligand value. Os(II) prefers to bind N(azo) (Os-N(azo), 1.98 Â) rather than N(imidazole) (Os-N(imidazole), 2.03 Â). EHMO calculations of ctc -OsCl 2 (MeaaiMe) and comparison with the ruthenium(II) complex account for the MLCT transitions in terms of a metal-dominated HOMO to a ligand-dominated LUMO shift. [ABSTRACT FROM AUTHOR]