Partial charge transfer contribution to the solvent isotope effect and photosensitized generation of singlet oxygen, O2(1Δg), by substituted ruthenium(ii) bipyridyl complexes in aqueous media

Abstract

The efficiency of singlet oxygen photosensitized by some ruthenium(ii) bipyridyl complex ions in aqueous media is reported in this study. Measurements were carried out in H2O and D2O. The effect of the deuterium isotope on the lifetime of (3)MLCT excited states of these complexes is studied in H2O and D2O. The deuterium isotope effect was discussed in terms of the vibronic coupling to the solvent in addition to the charge transfer to the solvent mechanism due to their dependence on the oxidation potential of the sensitizer. Quenching rate constants, kq, for quenching of the (3)MLCT states of these ruthenium complex ions by molecular oxygen were found to be in the range of (2.08-3.84) × 10(9) M(-1) s(-1) in H2O and (1.69-3.48) × 10(9) M(-1) s(-1) in D2O. The efficiency of singlet oxygen, O2((1)Δg), production as a result of the (3)MLCT quenching by oxygen, f, is reported in D2O and found to be in the range 0.25-0.56. It has been found that the lifetime of the excited state is longer in D2O, τ, than in H2O, τ, which was related to partial charge transfer to the solvent in addition to the vibronic coupling mechanism. Mechanisms by which the excited states of these ruthenium complexes are quenched by molecular oxygen that shows the competition between charge transfer, non-charge transfer deactivation channels or energy transfer assisted charge transfer deactivation mechanisms are reported.

Singlet oxygen production by a polypyridine ruthenium (II) complex with a perylene monoimide derivative: A strategy for photodynamic inactivation of Candida albicans

“…Singlet oxygen ( 1 O 2 , 1 D g ), the lowest excited state of the dioxygen molecule, can be generated by photochemical and chemical processes [1][2][3][4][5][6]. The most common photochemical method involves energy transfer from a triplet excited photosensitizer ( 3 *PS).…”

“…The most common photochemical method involves energy transfer from a triplet excited photosensitizer ( 3 *PS). Many dyes, including some diimides [2][3][4] and metal complexes [3][4][5][6][7][8][9][10] can be used as photosensitizers for the production of 1…”

Surface Modification of Two‐Dimensional Metal–Organic Layers Creates Biomimetic Catalytic Microenvironments for Selective Oxidation

“…We studied the mechanism of the photocatalytic aerobic THF oxidation. Singlet oxygen was first ruled out as the oxidant, since Ru(bpy) 3 2+ , which is known to generate singlet oxygen, did not oxidize THF under the photocatalytic conditions.…”

Developments in PDT Sensitizers for Increased Selectivity and Singlet Oxygen Production

“…This is because of the relatively long lifetime of the triplet metal-to-ligand charge transfer states, 3 MLCT, of many Ru(II) coordination compounds that make these excited states susceptible to quenching by oxygen. It is been reported that the MLCT absorption mainly produces 1 MLCT that undergo ISC and populate 3 MLCT [127]. …”