La3+ and N co-doped TiO2, which contained paramagnetic N species, decomposed acetaldehyde under visible light irradiation. The number of the paramagnetic N species seemed to control the absorption of visible light and the activity.
Powders of TiO2 doped with a metal ion and N species were prepared by a polymerized complex method and the visible-light photocatalytic activities of the products are investigated. Of the metal ions studied (K+, Ca2+, Sr2+, Ba2+, Nb5+, Fe3+, Zn2+, and Al3+), the photocatalyst prepared with Sr2+ exhibits the highest activity for acetaldehyde decomposition under visible-light irradiation. Results obtained from x-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analyses suggest that the doped N species reside at interstitial lattice positions in the catalyst. It was also found by XPS and ESR measurements that the doped N species combine with lattice oxygen to give rise to a paramagnetic property. The visible-light response of the catalyst is driven by the formation of paramagnetic N species at interstitial positions in the TiO2 lattice.
A room-temperature reaction of Co(CH3CO2)2·4H2O with pyrimidine-2-thione (Hpymt), or eight kinds of their derivatives (mole ratio = 1 : 2.8—3.0) in methanol, was carried out in air. It was found that the substituent group at a 4-position in the pymt skeleton governs the product. The pymt and its derivatives, having an alkyl or an amino group as the 4-substituent, gave tris-type cobalt(III) complexes mer-[Co(N-S)3] in good yields. On the other hand, the 2-thiouracil derivatives, having an oxygen or a sulfur atom as the 4-substituent, produced only bis-type cobalt(II) complexes [Co(N-S)2]. Such different ligand behavior concerns the different electronic structures of the pyrimidine rings. The presence of three linkage isomers in mer-[Co(4-methyl-pymt)3] has been confirmed by 59Co NMR spectroscopy, and an important role of the CH···π attractive interaction has been found.
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