Structure, photophysics, electrochemistry and DFT calculations of [RuH(CO)(PPh3)2(coumarinyl-azo-imidazole)]

2-(Coumarinyl-6-azo)-4-R-imidazole (4-R-LH, 1) and 4-(coumarinyl-6-azo)-5-R-imidazole (5-R-LH, 2) (R = H, Me, Ph) are two classes of –NN–CN– ligands used to synthesize [RuH(CO)(PPh3)2(4-R-L)] (3) and [RuH(CO)(PPh3)2(5-R-LH)Cl] (4). The characterization of the complexes has been done by elemental analysis and spectroscopic methods, and X-ray characterization is reported for one representative complex. The redox properties of the complexes were studied by cyclic voltammetry. They are emissive at room temperature. DFT and time dependent-DFT calculations were performed to explain the electronic structure, spectral and redox properties of the complexes.

Graphical abstract[RuH(CO)(PPh3)2(coumarinyl-NN-imidazole)]0/+ complexes have been spectroscopically characterized and confirmed by X-ray structure determination. The cyclic voltammetry shows Ru(III)/Ru(II) and Ru(IV)/Ru(III) redox couples along with azoimine reduction. They are emissive at room temperature. Theoretical calculations explain the electronic structure, spectral and redox properties of the complexes.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Coumarinyl-azo-imidazole complexes of {RuH(CO)(PPh3)2} unit are reported. ► The X-ray diffraction measurement confirms the structure. ► The cyclic voltammetry shows metal oxidation and azoimine redox couples. ► The compounds are emissive. ► Theoretical calculation explains the spectral and redox properties.