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In this work, based on density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, we theoretically investigate the excited-state process of the 2-(6'-hydroxy-2'-pyridyl)benzimidazole (2HPB) system in acetonitrile and water solvents. Since acetonitrile is an aprotic solvent, it has no effect on the solvent-assisted excited-state proton transfer (ESPT) process. Therefore, the 2HPB molecule cannot transfer the proton in acetonitrile, which is consistent with previous experimental observation. On the other hand, 2HPB can combine one water molecule (which is a protic solvent), forming the 2HPB–H2O complex in the S0 state. After photoexcitation, the intermolecular hydrogen bonds O1H2···O3 and O3H4···N5 both get strengthened in the S1 state, which leads to the possibility of a water-assisted ESPT process. Further, the charge redistribution reveals the tendency of ESPT. By exploring the potential energy curves for the 2HPB–H2O complex in water, we confirm that a stepwise double proton transfer process occurs in the S1 state. Water-assisted ESIPT can occur along O1H2···O3 or O3H4···N5 because of their similar potential barriers. Based on the stepwise ESPT mechanism, we reinterpret the absorption and fluorescence spectra mentioned in the experiments and confirm the rationality of the water-assisted ESPT process.

In this work, using density functional theory and time-dependent density functional theory methods, we theoretically studied the excited-state behaviors of 3 novel 2-(2-hydroxyphenyl)benzothiazole (HBT) derivatives (HBT-H-H, HBT-CN-H, and HBT-CN-CN). Analyses about primary chemical structures such as bond lengths and bond angles, we found that all the intramolecular hydrogen bonds in these 3 structures should be strengthened in the S1 state upon the photoexcitation. Exploring the infrared vibrational spectra at the hydrogen bonds groups, we confirmed that nonsubstitutional HBT-H-H structure might play more important roles in the excited-state intramolecular proton transfer (ESIPT) reaction than HBT-CN-H and HBT-CN-CN. Further, investigating vertical excitation process, it can be revealed that charge redistribution involved in hydrogen bonding moieties could facilitate the ESIPT reaction. Based on constructing potential energy curves of both S0 and S1 states, we confirmed that the substituents on HBT systems can reasonably regulate and control the ESIPT processes because of the different potential energy barriers. We deem that this present work not only elaborates the different excited-state behaviors of HBT-H-H, HBT-CN-H, and HBT-CN-CN but also may play important roles in designing and developing new materials and applications involved in HBT systems in future.

Fine-particle rare-earth metal zirconates Ln 2 Zr 2 O 7 (Ln = La, Nd, Sm, Dy, Er) with cubic structure were prepared by stearic acid method. Zirconium nitrate and rare-earth nitrate were as raw materials, and stearic acid was used as solvent and dispersant. The as-prepared Ln 2 Zr 2 O 7 nanocrystals were characterized by XRD, FT-IR, TEM and HRTEM. The results showed that the preparation temperature was lowered (from 1500 °C to 800 °C) and the reaction time was shortened (from at least 10 h to 5 h) by stearic acid method, compared with transitional solid-state method. The photocatalytic activity of Ln 2 Zr 2 O 7 nanocrystals was evaluated by the photocatalytic degradation of methyl orange. With the increase of the atomic number, the photocatalytic activity trend of obtained Ln 2 Zr 2 O 7 (Ln = La, Nd, Sm, Dy, Er) nanocrystals was in agreement with the change trend of magnetic moment of the rare-earth metal ion. The photoactivity of Ln 2 Zr 2 O 7 was strongly dependent on Ln, decreasing in the sequence of Dy > Nd > Er > Sm > La.