ABSTRACT
A high yield synthetic route for the preparation of N6 coordinated heteroleptic Ir(III) complexes using bidentate polypyridyl type ligands is described. The complexes are near-blue emitters and show microsecond emission lifetimes, high emission quantum yields and have two quasi-reversible reduction processes between -1.0 and -1.3 V vs. Ag/AgCl.
Subject(s)
Coordination Complexes/chemical synthesis , Iridium/chemistry , Coordination Complexes/chemistry , Crystallography, X-Ray , Electrochemical Techniques , Electrodes , Ligands , Molecular Conformation , Quantum Theory , Silver/chemistry , Spectrophotometry , Time FactorsABSTRACT
Resonance Raman microspectroscopy is used to investigate dye-sensitized NiO(x) nanoparticle films to be used as photocathodes in tandem dye-sensitized solar cells. It is shown that rR microspectroscopy has potential for applications in quality assurance in such systems and also in integrated dye-sensitized solar cell modules. Here, ruthenium dye-sensitized NiO(x) nanoparticle layers were produced both as single and double NiO(x) films using a one or two-step deposition process, respectively. The distribution of the sensitizer on the surfaces was investigated by rR microspectroscopy. The chemical images obtained from rR microspectroscopy yield complementary information to bright field microscope pictures and provide detailed insight into the sensitization pattern e.g. in the vicinity of surface vacancies and other inhomogeneities. Furthermore, based on the mapping results the dye desorption kinetics upon addition of water has been analysed. Desorption on the single NiO(x) film is faster and more efficient than on the double film. These changes are attributed to binding sites on the NiO(x) surface that are passivated with regard to water penetration. This passivation is introduced by the second synthesis step in building the second film of NiO(x) on the glass substrate. Both findings highlight the potential of rR microspectroscopy for quality assurance of dye-sensitized solar cell electrodes.
ABSTRACT
The synthesis and characterisation of two terpyridine based ruthenium/palladium heteronuclear compounds are presented. The photocatalytic behaviour of the Ru/Pd complex containing the linear 2,2':5',2''-terpyridine bridge (1a) and its analogue the non-linear 2,2':6',2''-terpyridine bridge (2a) are compared together with the respective mononuclear complexes 1 and 2. Irradiation of 1a with visible light (e.g., 470 nm) results in the photocatalytic generation of dihydrogen gas. Photocatalysis was not observed with complex 2a by contrast. A comparison with the photocatalytic behaviour of the precursors 1 and 2 indicates, that while for 1a the photocatalysis is an intramolecular process, for the mononuclear precursors it is intermolecular. The photophysical and electrochemical properties of the mono- and heterobinuclear compounds are compared. Raman spectroscopy and DFT calculations indicate that there are substantial differences in the nature of the lowest energy (3)MLCT states of 1a and 2a, from which the contrasting photocatalytic activities of the complexes can be understood.
Subject(s)
Hydrogen/chemistry , Palladium/chemistry , Ruthenium/chemistry , Catalysis , Ligands , Photochemical ProcessesABSTRACT
A pyrazine bridged ruthenium/palladium bimetallic photocatalyst with peripheral 4,4'-dicarboxyethyl-2,2'-bipyridine ligands, EtOOC-RuPd, is reported, together with its 2,2'-bipyridine analogue. Upon irradiation with visible light, EtOOC-RuPd catalyses the production of hydrogen gas whereas the complex RuPd does not.
