Synthesis, Spectroscopic and Electrochemical Studies of Isomeric Dichloro-bis-[ N (1)-Alkyl-2-(Arylazo)Imidazole]-Osmium(II). Single Crystal X-ray Structures of Blue-Violet Dichloro-Bis-[ N (1)-Methyl-2-(Arylazo)Imidazole]-Osmium(II) Species

Ruthenium(II) bipyridine complexes bearing quinoline-azoimine (NN'N″) tridentate ligands: synthesis, spectral characterization, electrochemical properties and single-crystal X-ray structure analysis

Four octahedral ruthenium(II) azoimine-quinoline complexes having the general molecular formula [Ru(II)(L-Y)(bpy)Cl](PF6) {L-Y=YC6H4N=NC(COCH3)=NC9H6N, Y=H (1), CH3 (2), Br (3), NO2 (4) and bpy=2,2'-bipyrdine} were synthesized. The azoimine-quinoline based ligands behave as NN'N″ tridentate donors and coordinated to ruthenium via azo-N', imine-N' and quinolone-N″ nitrogen atoms. The composition of the complexes has been established by elemental analysis, spectral methods (FT-IR, electronic, (1)H NMR, UV/Vis and electrochemical (cyclic voltammetry) techniques. The crystal structure of complex 1 is reported. The Ru(II) oxidation state is greatly stabilized by the novel tridentate ligands, showing Ru(III/II) couples ranging from 0.93-1.27 V vs. Cp2Fe/Cp2Fe(+). The absorption spectrum of 1 in dichloromethane was modeled by time-dependent density functional theory (TD-DFT).

Syntheses, crystal structures, MMCT and magnetic properties of four one-dimensional cyanide-bridged complexes comprised of MII–CN–FeIII (M = Fe, Ru, Os)

Four 1D cyanide-bridged complexes [cis-M^II(L)₂(CN)₂Fe^III(salen)](PF₆) (3–6) have been synthesized, of which 3 and 4 are Class II mixed-valence complexes.

Heteroleptic tris-chelates of ruthenium(II): synthesis, spectral characterisation and electrochemical properties

A facile reaction of cis-trans-cis-RuCl(2)(RaaiR')(2) [RaaiR'=1-alkyl-2-(arylazo)imidazole, m-R-C(6)H(4)-NN-C(3)H(2)-NN-1-R', where R=H (a), OMe (b), NO(2) (c) and R'=Me (1), Et (2) and CH(2)Ph (3)] either with 2,2'-bipyridine (bpy) and AgNO(3) followed by NaClO(4) or [Ag(bpy)(2)](ClO(4)) in boiling acetone has isolated red-brown [Ru(bpy)(RaaiR')(2)](ClO(4))(2) (1a-c, 2a-c, 3a-c). The maximum molecular peak of [Ru(bpy)(OMeaaiMe)(2)](ClO(4))(2) (1b) is observed at m/z 888.01 (100%) in the FAB mass spectrum. IR spectra of the complexes show CN and NN stretching at 1590 and 1370cm(-1) which is red shifted by 40 and 90cm(-1) from the free ligand value supports Ru-azo nitrogen pi bonding interaction. The emission spectra in frozen glass (77K) are sharper and considerably more intense than the room temperature spectra. The (1)H NMR spectral measurements suggest methylene, -CH(2)-, in RaaiEt gives a complex AB type multiplet while in RaaiCH(2)Ph it shows AB type quartets. Considering two arylazoimidazole moieties there are 20 different carbon atoms in the molecule which gives a total of 20 different peaks in the (13)C NMR spectrum. In the (1)H-(1)H COSY spectrum of the present complexes, absence of any off-diagonal peaks extending from delta=14.12 and 9.55ppm confirm their assignment of no proton on N(1) and N(3), respectively. Contour peaks in the (1)H-(13)C HMQC spectrum in the present complexes, the absence of any contours at delta=147.12, 160.76, 155.67 and 157.68 ppm assign them to the C(2), C(6), C(8) and C(e and e'') carbon atoms, respectively. Cyclic voltammogram shows Ru(III)/Ru(II) redox couple along with three successive ligand reductions. The plot of difference in potential of first oxidation and reduction versus energy of main MLCT band (nu(CT)) is linear. Electrochemical parametrisation of Ru(III)/Ru(II) redox couple determines ligand potential E(L)(L).