Synthesis, characterization and photovoltaic studies of 2,2′;6′,2ʺ-terpyridine-based ruthenium complexes with phenylamino, anthranyl and furfuryl substitutions at the 4′-position

A series of two heteroleptic ruthenium complexes of the type [Ru(X-tpy)(bpy-COOH)(NCS)](PF6) (where X-tpy = 4′-(4-N,N-dimethylaminophenyl)-2,2′:6′,2ʺ-terpyridine for complex 1 and 4′-(9-anthryl)-2,2′:6′,2ʺ-terpyridine for complex 2, bpy-COOH = 4,4′-dicarboxy-2,2′-bipyridine) and another heteroleptic ruthenium complex of the type [Ru(X-tpy)(bpy-COOH)(NCS)]Cl (where X-tpy = 4′-(furan-2-yl)-2,2′:6′,2ʺ-terpyridine for complex 3, bpy-COOH = 4,4′-dicarboxy-2,2′-bipyridine) have been synthesized and fully characterized. The effects of these substitutions with varying electronic properties on the resulting ruthenium dyes were studied in relation to their electronic structure and consequent redox chemistry and photovoltaic performance in a DSSC setup. Complex 1 registers a better photovoltaic performance with photon to conversion efficiency (PCE) of (η = 1.41%) with a Jsc value of 2.1 mA cm−2 and Voc 0.58 V followed by 2 (η = 0.44%) and 3 (η = 0.13%). The pattern for the photovoltaic performance has been justified with a theoretical analysis of the directionality of the most intense charge transfers taking place in the dyes upon light irradiation.