Synthesis, photophysical and electrochemical properties of a mixed bipyridyl-phenanthrolyl ligand Ru(II) heteroleptic complex having trans-2-Methyl-2-butenoic acid functionalities

Abstract

In this work, two ligands: 4-(trans-2-Methyl-2-butenoic acid)-2,2'-bipyridine) (L1) and 5-(trans-2-methyl-2-butenoic acid)-1,10-phenanthroline (L 2), with the corresponding mixed-ligand heteroleptic Ru(II) complex were synthesized and characterized by FT-IR, 1H-, 13C-NMR spectroscopy and elemental analysis. The influence of the mixed functionalized polypyridyl ruthenium(II) complex on the photophysical and electrochemical properties were investigated and compared to individual single-ligand homoleptic complexes. Interestingly, the mixed-ligand complex formulated as [RuL1L 2(NCS) 2] exhibits broad and intense metal-to-ligand charge transfer (MLCT) absorption with a high molar extinction coefficient (λ max = 514 nm, ε = 69,700 M -1 cm -1), better than those of individual single-ligand complexes, [Ru(L1) 2(NCS) 2] and [Ru(L 2) 2(NCS) 2], and a strong photoluminescence intensity ratio in the red region at λ em = 686 nm. The electrochemical properties of the complex indicated that the redox processes are ligand-based.