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

The 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 electronic 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. The p-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.