Journal of the American Chemical Society, Vol.139, No.25, 8412-8415, 2017
Engineering High-Potential Photo-oxidants with Panchromatic Absorption
Challenging photochemistry demands high-potential visible-light-absorbing photo-oxidants. We report (i) a highly electron-deficient Ru(II) complex (eDef-Rutpy) bearing an E-1/2(0/+) potential more than 300 mV more positive than that of any established Ru(II) bis(terpyridyl) derivative, and (ii) an ethyne-bridged eDef-Rutpy-(porphinato)Zn(II) (eDef-RuPZn) supermolecule that affords both panchromatic UV-vis spectral domain absorptivity and a high E-1/2(0/+) potential, comparable to that of Ce(NH4)(2)(NO3)(6) [E-1/2(Ce3+/(4+)) = 1.61 V vs NHE], a strong and versatile ground-state oxidant commonly used in organic functional group transformations. eDef-RuPZn exhibits similar to 8-fold greater absorptive oscillator strength over the 380-700 nm range relative to conventional Ru(II) polypyridyl complexes, and impressive excited-state reduction potentials (E-1(-/*) = 1.59 V; 3E(-/*) = 1.26 V). eDef-RuPZn manifests electronically excited singlet and triplet charge-transfer state lifetimes more than 2 orders of magnitude longer than those typical of conventional Ru(II) bis(terpyridyl) chromophores, suggesting new opportunities in light-driven oxidation reactions for energy conversion and photocatalysis.