Synthesis, structure, and photophysical and electrochemical properties of Ru(II) complexes of arylene-vinylene terpyridyl conjugates

A series of arylene-vinylene pi-conjugated terpyridyl ruthenium(II) complexes, [Ru(PPh3)(2)Cl(tpy-C6H4-CH=CH- Ar)][PF6] (1-4; tpy = 2,2': 6', 2 ''-terpyridyl, where Ar = phenyl, tolyl, 1-naphthyl and 9-anthracenyl as substituents at the 4' position of tpy), have been synthesized and characterized by multinuclear NMR, IR, HRMS and single crystal X-ray crystallography. The influence of the electronic nature of arylene groups on their photophysical and electrochemical properties has been investigated to understand the electronic interaction between the metal-organic redox centers. Furthermore, a sigma-donor phenylacetylide group has been incorporated to accomplish [Ph-C equivalent to C-Ru(PPh3)(2)(tpy-C6H4-CH=CH-Ar)][PF6] (5-8) complexes by the substitution of a coordinated chloride ligand and to investigate the change in their redox and photophysical properties. DFT studies have been performed to gain an insight into their electronic properties by determining the HOMO-LUMO energy levels and frontier molecular orbitals of all the synthesized Ru(II) complexes.