RESUMEN
Phenazine-2,3-diol-based dyes, KY-1Na and KY-2Na bearing one and two carboxylic acid sodium salts, respectively, have been newly developed as water-soluble photosensitizers (PSs) possessing the ability to generate singlet oxygen (1O2). In order to evaluate the solubility of KY-1Na and KY-2Na in water, the hydrophobicity/hydrophilicity of the two PSs was investigated by experimental measurement of the logarithms (log Po/w) of the 1-octanol/water partition coefficient (Po/w) for the PS. The log Po/w values of both KY-1Na and KY-2Na were determined to be -0.9, indicating that both the PSs are more hydrophilic than Rose Bengal (-0.6) and have hydrophilicity equivalent to methylene blue (-0.9). Both the PSs in water show a broad photoabsorption band in the range of 500 to 600 nm. Thus, we estimated the 1O2 quantum yields (ΦΔ) of KY-1Na and KY-2Na in water by using 9,10-anthracenediyl-bis(methylene)dimalonic acid (ABDA) as a water-soluble 1O2 scavenger. It was found that in water the ΦΔ value (0.19) of KY-2Na is higher than that of KY-1Na (0.06). Density functional theory (DFT) calculations suggested that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) distributions for the molecular structure of KY-2Na are adequately separated, leading to a decrease in the energy gap (ΔEST) between the singlet state (S1) and the triplet state (T1) that causes efficient intersystem crossing (ISC), compared to that for the molecular structure of KY-1Na. Indeed, time-dependent DFT (TD-DFT) calculations demonstrated that the ΔEST(S1-T1) value (0.82 eV) of KY-2Na is smaller than that (0.98 eV) of KY-1Na, resulting in a relatively high ΦΔ value of KY-2Na. Consequently, we demonstrate that phenazine-2,3-diol-based PSs bearing carboxylic acid salts possess high solubility and moderate 1O2 generation ability in water.
RESUMEN
Active reaction centers for ammonia on titanium oxyhydroxide were explored to direct the search for an efficient sol-gel method for the synthesis of a titanium oxynitride (TiO2-xNx) sample with an efficient responsiveness to the visible light constituting a main part of the solar spectrum. The results lead to the conclusion that the site giving IR bands at around 2195 cm(-1) for the adsorbed CO molecules at 300 K is a reactive site and behaves as Lewis acid site in the coordination environment of distorted five-coordinate Ti4+ ions. Ammonia molecules are adsorbed on such a site to form -NH2 and -OH species during the heat treatments at a temperature above 373 K, and they are ultimately incorporated into the TiO2 lattice as nitride through the dehydration at higher temperatures of up to 723 K, resulting in the formation of an anatase type of TiO2-xNx.
