Photoreactions of spirophenanthrooxazine dispersed in polystyrene film at room temperature

Spectroscopic and optical properties of 1,2,4-triazolo[4,3-a]pyridin-3(2H)-one as a component of herbicides

The herbicides azafenidin [(2-(2,4-dichloro-5-prop-2-ynoxyphenyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyridin-3-one)] and flumetsulam [(N-(2,6-difluorophenyl)-5-methyl-[1,2,4]triazolo[1,5-a]pyrimidine-2-sulfonamide)] were subjected to IR, Raman, UV-Vis and emission studies. As triazolopyridine is the most prominent and active component of these herbicides, this molecule was characterised by XRD studies, FTIR, Raman, UV-Vis and emission spectra. The experimental data were compared to the results of the DFT quantum chemical calculations carried out for its optimised structure, IR intensities and Raman activities, HOMO-LUMO transitions, and energies of the singlet and triplet states. The characteristics for triazolopyridine quantities were used in the analysis of the studied herbicides.

Photocontrol of ion permeation in lipid vesicles with (bola)amphiphilic spirooxazines

(Bola)amphiphilic spirooxazines have been prepared and photocontrol of ion permeation was observed in lipid vesicles.

THEORETICAL INVESTIGATION OF SUBSTITUTION EFFECT ON THE PROTON TRANSFER MECHANISM IN 3-MERCAPTO-PROPENETHIAL

We present detailed theoretical studies of the proton transfer (PT) in the 3-Mercapto-propenethial (MP) and in some of its derivatives. The effect of substitution on the transition state structures corresponding to the PT in R2 or R1(3) positions is studied by using B3LYP/6-311++G** level of theory in gas phase and water solution. The following substituents have been taken into consideration: Cl, F, OH, SH, OCH3, SCH3, CHO, NO2, CCH and OCF3 . For the different derivatives of 3-MP, we have computed geometries and potential energy curves for the intramolecular PT in their ground. Also, the excited-state properties of intramolecular hydrogen bonding in substituted systems have been investigated theoretically using the time-dependent density functional theory method. The π-electron delocalization parameter (Q) and HOMA index as a geometrical indicator of a local aromaticity are investigated. Natural bond orbital (NBO) analysis was also performed for better understanding the nature of intramolecular interactions. The results of analysis by Quantum theory of "Atoms in Molecules" and NBO method fairly support the DFT results. Correlations between the PT reaction barrier versus topological parameters, ν(S–H) and γ(S–H) are also probed. The obtained results showed a strong influence of the R substituent on the PT reaction barrier changes. Numerous correlations between topological, geometrical, thermodynamic properties and energetic parameters were also found.

Time-dependent density functional theory (TD-DFT) study on the excited-state intramolecular proton transfer (ESIPT) in 2-hydroxybenzoyl compounds: significance of the intramolecular hydrogen bonding

The excited-state properties of intramolecular hydrogen bonding (IMHB) in methyl salicylate (MS) and its effects on the excited-state intramolecular proton transfer (ESIPT) have been investigated using theoretical methods. From the geometric optimization and IR spectra in the ground and excited states calculated by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods respectively, the IMHB is demonstrated to be significantly strengthened upon excitation to excited state S(1). Thereby, the ESIPT is facilitated by the excited-state IMHB strengthening since ESIPT takes place through IMHB. In addition, the absorption and fluorescence peaks of the S(1) state are also calculated using the TD-DFT method. It is noted that the calculated spectra are in good agreement with the experimental results, which has confirmed the ESIPT mechanism of MS first proposed by Weller. Moreover, other four 2-hydroxybenzoyl compounds forming strong IMHB are investigated to understand the effect of substituent R on the ESIPT process. We find that the hydrogen bond strength can be controlled by the inductive field effect of the substituent. Thus it is inferred that the ESIPT reaction can be facilitated by the inductive effect of electron-donating substituent.

Photochromism of a spirooxazine in the single crystalline phase

The single crystals of a closed form spirooxazine spiro[azahomoadamantane-isoquinolinoxazine] were found for the first time to undergo photocoloration processes consistent with photochromism in the single crystalline phase.