Electronic Characterization of Vis –NIR Absorbing Noninnocent Ruthenium Oxyquinolate–merocyanine Complexes and their Photoacoustic Emission in Aqueous Micellar Solution

A series of bis-heteroleptic ruthenium(II) polypyridyl dyes incorporating π-accepting 5-(vinyl-cyanine)-8-oxyquinolate ligands are reported. Trends in the HOMO–LUMO bandgap exhibit an excellent correlation with increasing electron-acceptor strength of the terminal cyanine moiety. Intense vis–NIR molar extinction coefficients combined with rapid nonradiative decay, im parted by mixing of the Ru(dπ) − OQN(π) frontier orbitals, makes these complexes highly suited to photoacoustic applications. AbstractThe electronic and photophysical properties for a series of ruthenium(II) polypyridyl dyes are presented where a π-accepting 5-(vinyl-cyanine)-8-oxyquinolate class of ligand is incorporated to yield an improved vis–NIR absorption. A combination of computational, UV–vis–NIR absorption, phosphorescence emission and cyclic voltammetry studies are used to probe the influence of these ligands on complex elec tronic and photophysical properties. To assess their potential as vis–NIR photoacoustic contrast agents, select complexes were formulated in a PBS buffer/Tween® 20 solvent system. Thep-quinolin-1-ium, 1,3,3-trimethyl-3H-indol-1-ium and 1,1,3-trimethyl-1H-benzo[e]indol-3-ium acceptor groups each impart a strong 680  nm optical absorption and photoacoustic emission on par with the performance exhibited by both the methylene blue and cryptocyanine commercial dyes.

Source: Photochemistry and Photobiology - October 18, 2022 Category: Science Authors: Peter Catsoulis, Shengwei Wang, Chandra Yelleswarapu, Jonathan Rochford Tags: Special Issue Research Article Source Type: research