Wirelike dinuclear ruthenium(II)polyterpyridine complexes based on D–P–A architecture: Experimental and theoretical investigation

Abstract

Abstract To accomplish the goal of prolonged excited state, efficient for interfacial electron injection and low electron-hole recombination (LUMO → HOMO of complex) we have synthesized a heteroleptic complexes 1 and 2 based on D–P–A architecture (where P = Photosensitizer, A = Acceptor and D = Donor). The complexes 1 and 2 show the average excited state lifetimes (τavg) of 25 ns and 12.67 ns respectively compared to 0.25 ns for [Ru(tpy)2]2PF6. The τavg of such an order is sufficient for performing the interfacial electron transfer into the conduction band of TiO2 and redox chemistry of excited state. The electrochemical studies exhibit the oxidation potential (Eox) of 1.23 V and 1.27 V vs SCE with associated excited-state redox potentials ( E o x * = − 0.95 V and −0.85 V and E r e d * = 1.0 V and 0.88 V for complexes 1 and 2 respectively) have evidence for stronger reductant and oxidant behaviour in 1MLCT excited state. Subsequent interfacial study with TiO2 nanocrystal is in good agreement with photo induced electron injection from LUMO of complex to conduction band (CB) of TiO2 as LUMO level (−3.22 eV and 3.16 eV for complexes 1 and 2 respectively) of complexes is above the CB of TiO2 (−3.65 eV). The experimental photophysical results of both the complexes are well supported by time dependent density functional theory.