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Protonation, charging, and field effects on the thermal isomerization of a nitrospiropyran (SP) modified by a thiolated etheroxide chain into merocyanine (MC) are computationally studied at the DFT level. The ring opening leads to cis-MC conformers that then isomerize to the more stable trans forms. While the closed neutral spiropyran is more stable than the conjugated open forms, the merocyanine conformers are significantly stabilized by protonation, electron attachment, and ionization. For protonation on the pyran oxygen atom and electron attachment, the MC conformers are more stable than SP, and unlike for the neutral species, the ring opening is spontaneous at room temperature. Moreover, for the pyran oxygen-protonated form, the ring opening to the cis-merocyanine becomes barrierless. On the other hand, barriers comparable to the neutral remain along the thermal pathway to the cis-merocyanine conformer for ionization or electron attachment, and the barrier for isomerization is significantly higher for the N-protonated SP form. External field effects on the neutral reaction path show that ring opening to the cis-merocyanine is favored when the field reduces the electron density on the pyran part, as also induced by the local field due to O protonation. 相似文献
64.
In Chan Baek Muga Vithal Jeong Ah Chang Jun-Ho Yum Md.K. Nazeeruddin Michael Grätzel Yong-Chae Chung Sang Il Seok 《Electrochemistry communications》2009,11(4):909-912
A simple one-step heat-treatment of peroxotitanate complex aqueous solution at around 100 °C was resulted in the formation of ellipsoidal anatase TiO2 nanoparticles having a high aspect ratio with no branches. The length of these ellipsoidal TiO2 falls in the range of 200–350 nm, depending on mole ratio of Ti4+/H2O2. Dye-sensitized solar cell based on these ellipsoidal nanocrystalline TiO2 as photoanode was fabricated and characterized. 相似文献
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The luminescence properties of K(1/2)Bi(1/2)TiO(3):Pr(3+) and Na(1/2)Bi(1/2)TiO(3):Pr(3+) powders are investigated in the temperature range 10-600 K. The experimental data are interpreted on the basis of metal-to-metal charge transfer processes and by considering Bi(3+)-to-Pr(3+) sensitization effects. 相似文献
67.
Ujashkumar A. Shah Hemantkumar S. Deokar Shivajirao S. Kadam Vithal M. Kulkarni 《Molecular diversity》2010,14(3):559-568
Cyclooxygenase-2 (COX-2) inhibitors are widely used for the treatment of pain and inflammatory disorders such as rheumatoid
arthritis and osteoarthritis. A series of novel 2-(4-methylsulfonylphenyl)pyrimidine derivatives has been reported as COX-2
inhibitors. In order to understand the structural requirement of these COX-2 inhibitors, a ligand-based pharmacophore and
atom-based 3D-QSAR model have been developed. A five-point pharmacophore with four hydrogen bond acceptors (A) and one hydrogen
bond donor (D) was obtained. The pharmacophore hypothesis yielded a 3D-QSAR model with good partial least-square (PLS) statistics
results. The training set correlation is characterized by PLS factors (r
2 = 0.642, SD = 0.65, F = 82.7, P = 7.617 e − 12). The test set correlation is characterized by PLS factors (Q
2
ext = 0.841, RMSE = 0.24,Pearson−R = 0.91). A docking study revealed the binding orientations of these inhibitors at active site amino acid residues (Arg513,
Val523, Phe518, Ser530, Tyr355, His90) of COX-2 enzyme. The results of ligand-based pharmacophore hypothesis and atom-based
3D-QSAR give detailed structural insights as well as highlights important binding features of novel 2-(4-methylsulfonylphenyl)pyrimidine
derivatives as COX-2 inhibitors which can provide guidance for the rational design of novel potent COX-2 inhibitors. 相似文献
68.
Summary We characterize codense and completely codense ideals. 相似文献
69.
One pot green synthesis of 1‐(1,2,4‐triazol‐4‐yl)spiro[azetidine‐2,3′‐(3H)‐indole]‐2′,4′(1′H)‐diones was carried out by the reaction of indole‐2,3‐diones,4‐amino‐4H‐1,2,4‐triazole and acetyl chloride/chloroacetyl chloride in ionic liquid [bmim]PF6 with/without using a catalyst. It was also prepared by conventional method via Schiff's bases, 3‐[4H‐1,2,4‐triazol‐4‐yl]imino‐indol‐2‐one. Further, the corresponding phenoxy derivatives were obtained by the reaction of chloro group attached to azetidine ring with phenols. The synthesized compounds were characterized by analytical and spectral (IR, 1H NMR, 13C NMR, and FAB mass) data. Evaluation for insecticidal activity against Periplaneta americana exhibited promising results. 相似文献
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