Vectorial Electron Transfer in Donor–Photosensitizer–Acceptor Triads Based on Novel Bis‐tridentate Ruthenium Polypyridyl Complexes

Abstract

The first examples of rodlike donor-photosensitizer-acceptor arrays based on bis-2,6-di(quinolin-8-yl)pyridine Ru(II) complexes 1a and 3a for photoinduced electron transfer have been synthesized and investigated. The complexes are synthesized in a convergent manner and are isolated as linear, single isomers. Time-resolved absorption spectroscopy reveals long-lived, photoinduced charge-separated states (tau(CSS) (1a)=140 ns, tau(CSS) (3a)=200 ns) formed by stepwise electron transfer. The overall yields of charge separation (> or = 50% for complex 1a and > or = 95% for complex 3a) are unprecedented for bis-tridentate Ru(II) polypyridyl complexes. This is attributed to the long-lived excited state of the [Ru(dqp)(2)](2+) complex combined with fast electron transfer from the donor moiety following the initial charge separation. The rodlike arrangement of donor and acceptor gives controlled, vectorial electron transfer, free from the complications of stereoisomeric diversity. Thus, such arrays provide an excellent system for the study of photoinduced electron transfer and, ultimately, the harvesting of solar energy.

Crystalline Non‐Equilibrium Phase of a Cobalt(II) Complex with Tridentate Ligands

“…With ruthenium(II) as metal center and flexible chelate ligands such as ddpd (ddpd, N , N′ ‐dimethyl‐ N , N′ ‐dipyridine‐2‐yl‐pyridine‐2,6‐diamine)3e–3g or dqp {dqp = 2,6‐di(quinolin‐8‐yl)pyridine},3a–3d several substitutionally inert stereoisomers are formed, which have to be separated (Scheme ). An exception seems to be the dcpp ligand [dcpp, 2,6‐bis(2‐carboxypyridyl)pyridine], which has only shown meridional coordination in M(dcpp) 2 complexes so far 3h,5,6.…”

Thermal and Photoinduced Electron Transfer in Directional Bis(terpyridine)ruthenium(II)–(Bipyridine)platinum(II) Complexes

“…[9,10] Low-emission quantum yields and low excited-state lifetimes at room temperature in fluid solution result in less useful complexes within the field of photoinduced electron transfer (PET) or energy transfer. [11][12][13] Efforts to improve the photophysical properties of Ru II complexes with tridentate ligands were made by increasing the bite angles of the chelate ligands [14][15][16][17][18] and by tuning HOMO and LUMO energies by adding push-pull substituents to the ligand periphery. [19][20][21][22][23][24] Employing heteroleptic [Ru(bpy)(bpy-X)(bpy-Y)] 2+ complexes with two (or more) differently substituted bpy to ruthenium is observed in 2 but not in 1 (light harvesting).…”

Zn(II)‐Protoporphyrin IX‐Based Photosensitizer‐Imprinted Au‐Nanoparticle‐Modified Electrodes for Photoelectrochemical Applications

“…The successful generation of high‐affinity molecular‐imprinted sites for Zn(II)‐PP‐IX in the bis aniline‐crosslinked Au NPs matrix, and the enhanced photocurrents observed upon binding the photosensitizer Zn(II)‐PP‐IX to the imprinted sites, suggest that by the appropriate structural modification of the photosensitizer, the resulting photocurrents could be improved. Numerous studies have implemented photosensitizer‐electron acceptor dyads, triads, tetrads, or electron donor/photosensitizer/electron acceptor triads, as supra­molecular nanostructures that mimic the electron transfer reactions of the native photosynthetic apparatus. The stepwise electron transfer processes in these systems lead to the spatial separation of the photogenerated reduced and oxidized species, thus retarding the destructive back electron transfer reactions, and enhancing the yields of photocurrent efficiencies.…”