Differential infrared absorption spectroscopy was used to study the formation of isocyanates and further photo-products in the oligonucleotides dG10, dC10 and dT10 and in their mononucleosides by ultraviolet light at 266 nm. We find that α-cleavage takes place in oligonucleotides and mononucleosides both in films and in solution. The very intense and spectrally isolated isocyanate (N=C=O) asymmetric stretch vibration at 2277 cm(-1) is used as a spectroscopic marker for detection of the photo-product. The band disappears upon reaction with small amounts of water vapour as expected for isocyanates. Quantum yields for isocyanate formation by nucleobase ring cleavage in the α-position to the carbonyl group are ∼5 × 10(-5) in the mononucleosides and up to 5 × 10(-4) in the oligonucleotides. In the mixed oligonucleotides dG10/dC10 and dA10/dT10 the quantum yield of α-cleavage drops by a factor of 10 compared to the single oligonucleotides. Implications for DNA repair and photo-induced DNA-protein cross-linking via isocyanate reaction with NH2 groups of amino acids are discussed.

Photocatalytic splitting of water was carried out in a two-phase system. The efficiencies of different types of nanocrystalline semiconductors were investigated and compared with commercialised TiO 2 nanopowder. Generated hydrogen was chemically stored by use of a quinoid system, which seems to be useable for fuel cells. Solar light sensitive nanocomposites of CdSe/TiO 2 and CdS x Se y /TiO 2 type were prepared and their good photocatalytic performance was demonstrated. In the visible range of 400 -600 nm CdS x Se y /TiO 2 composites show comparable good results as in the UV range, which is very promising for their use as solar light water splitters. The concept of sensitising TiO 2 with different kind of semiconductor nanoparticles, which is already known from quantum dot sensitised solar cells (QDSC), was demonstrated here for water splitting as well. Furthermore the kinetics of the storage reaction was investigated by UV-Vis spectroscopy and found to proceed via a consecutive reaction with an 1:1 charge transfer complex of quinone and hydroquinone as intermediate. The electron transfer process via a Fe 2+ /Fe 3+ redox couple was investigated by UV-Vis spectroscopy as well as by a dye reaction on the TiO 2 surface. A light microscopic view of the surface of larger aggregates of TiO 2 nanoparticles indicated different areas of photocatalytic activity with photocatalysis preferentially at catalyst edges. The global electron transfer process could be traced by following the dye colour in real time.

Rotationally resolved electronic spectra of seven vibrationally excited bands in the electronic spectrum of benzimidazole have been measured and analyzed. From the vibrational contributions to the rotational constants, an assignment of the hot bands could be made on the basis of anharmonic corrections to the harmonic normal modes and by using the information contained in the Duschinsky matrix calculated by second order coupled cluster (CC2) theory. Fluorescence emission and (hot) absorption spectra of benzimidazole from Jalviste and Treshchalov [Chem. Phys. 1993, 172, 325] have been simulated using Franck-Condon integrals obtained from CC2 optimized geometries and Hessians.