title: Photosensitization of nanoparticulate TiO2 using a Re(I)-polypyridyl complex: studies on interfacial electron transfer in the ultrafast time domain.
abstract: We have synthesized a new photoactive rhenium(i)-complex having a pendant catechol functionality [Re(CO)(3)Cl(L)] (1) (L is 4-[2-(4'-methyl-2,2'-bipyridinyl-4-yl)vinyl]benzene-1,2-diol) for studying the dynamics of the interfacial electron transfer between nanoparticulate TiO(2) and the photoexcited states of this Re(i)-complex using femtosecond transient absorption spectroscopy. Our steady state absorption studies revealed that complex 1 can bind strongly to TiO(2) surfaces through the catechol functionality with the formation of a charge transfer (CT) complex, which has been confirmed by the appearance of a new red-shifted CT band. The longer wavelength absorption band for 1, bound to TiO(2) through the proposed catecholate functionality, could also be explained based on the DFT calculations. Dynamics of the interfacial electron transfer between 1 and TiO(2) nanoparticles was investigated by studying kinetics at various wavelengths in the visible and near infrared regions. Electron injection into the conduction band of the nanoparticulate TiO(2) was confirmed by detection of the conduction band electron in TiO(2) ([e(-)](TiO(2)(CB))) and the cation radical of the adsorbed dye (1˙(+)) in real time as monitored by transient absorption spectroscopy. A single exponential and pulse-width limited (<100 fs) electron injection was observed. Back electron transfer dynamics was determined by monitoring the decay kinetics of 1˙(+) and .
authors.affiliation: Central Salt and Marine Chemicals Research Institute (CSIR), Bhavnagar 364002, Gujarat, India.
authors.forename: Prasenjit
authors.initials: P
authors.lastname: Kar
authors.forename: Tanmay
authors.initials: T
authors.lastname: Banerjee
authors.forename: Sandeep
authors.initials: S
authors.lastname: Verma
authors.forename: Anik
authors.initials: A
authors.lastname: Sen
authors.forename: Amitava
authors.initials: A
authors.lastname: Das
authors.forename: Bishwajit
authors.initials: B
authors.lastname: Ganguly
authors.forename: Hirendra N
authors.initials: HN
authors.lastname: Ghosh