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Anbarasan Kalaiselvan Ponnambalam Venuvanalingam Jordi Poater Miquel Sol 《International journal of quantum chemistry》2005,102(2):139-146
The stereochemical course of the deamination of cis‐2,3‐dimethylaziridine by nitrosyl chloride was investigated at the QCISD/6‐31G(d) level. Calculations reveal that the reaction takes place in two steps. In the first step, the reactants form a pre‐reactive complex, followed by a spiro‐type bicyclic transition state, which on dissociative cycloelimination gives the N‐nitrosoaziridine intermediate. In the second step, this intermediate undergoes cycloreversion through a slightly asynchronous concerted transition state to form an alkene with the same stereochemistry, which is in total agreement with experiment. In the whole reaction, the denitrosation step is found to be rate‐determining. For comparison, geometry optimizations and energies were also obtained at the B3LYP/6‐31G(d) level. It was found that the B3LYP energy results differed significantly from the QCISD ones. To analyze the reason for this difference, B3LYP calculations were repeated by varying the contribution of exact exchange in the Becke functional. With respect to the QCISD results, it has been shown that the functional with 0% exact exchange yields the best activation barriers, whereas the functional with 30% exact exchange is the most suitable one to carry out the complexation and reaction energy calculations. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 相似文献
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Kalaiselvan A Ammal SC Venuvanalingam P Yamataka H 《The journal of physical chemistry. A》2005,109(21):4829-4835
cis-2,3-Dimethylaziridine reacts with difluoroamine to give the corresponding alkene and nitrogen with retention of configuration. We have carried out a DFT study of this reaction to clarify the reaction mechanism by considering a multistep reaction pathway with possible intermediacy of several three- and four-membered cyclic intermediates and transition states (TSs). The energetics of this reaction shows that the reaction takes place in four steps including a three-membered azamine intermediate. Both the energetics and the stereochemical outcome of this reaction rule out the formation of a four-membered diazetine intermediate during the reaction. Although the first N-N bond formation step is rate determining, the final step, asynchronous concerted cleavage of the azamine intermediate, explains the stereochemistry of this reaction. The asynchronous nature of the final step makes the reaction Woodward-Hoffmann allowed, as reported by Yamabe and Minato (J. Phys. Chem. A 2001, 105, 7281). Computations at HF and MP2 levels confirm the same trends in energetics. Single point energy computations at B3LYP, MP2, and QCISD levels with the 6-311++G(d,p) and cc-pVTZ basis sets show that the larger basis sets predict higher free energies of activation and less negative free energies of reaction. Intrinsic reaction coordinate (IRC) analyses reveal the asynchronous nature of the first and the last steps of the reaction. The deamination of trans-2,3-dimethylaziridine was shown to follow a course of reaction similar to that of the cis isomer. 相似文献
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Arunkumar Ammasi Shanavas Shajahan Acevedo Roberto Anbarasan Ponnusamy Munusamy 《Structural chemistry》2020,31(3):1029-1042
Structural Chemistry - A new series of triphenylamine (TPA)-based organic dyes (A1-A4) are characterized and implemented as photosensitizers for dye-sensitized solar cells (DSSCs). In the... 相似文献
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R. Anbarasan V. Sangeeth M. Saravanan R. Rajkumar M. Anandhaalaguraja V. Dhanalakshmi 《Journal of Macromolecular Science: Physics》2013,52(4):704-719
Effects of substituents and dopants on the structure–property relationships of poly(aniline) (PANI)-type homopolymers are analyzed. The gravimetric method was used for the estimation of rate of polymerization (Rp). FTIR spectroscopy was used for the calculation of relative intensities (RI) of benzenoid (RI[B/CH]), quinonoid (RI[Q/CH]), and their internal conversion (RI[B/Q]). Thermogravimetric analysis (TGA) characterized the thermal stability of PANIs. A standard four probe method was employed for the conductivity measurements. The results are analyzed and critically compared. 相似文献
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The palladium-catalyzed cyanation of Ar-X (X = I, Br, Cl, OTf, and H) allows for an efficient access towards benzonitriles. After its discovery in 1973 and following significant improvements in recent decades, this methodology has become nowadays the most popular for preparation of substituted aromatic nitriles. In this critical review, we summarize the important developments in this area from 2000 until 2010 (151 references). 相似文献
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A series of novel organic dyes (ICZA1, ICZA2, ICZA3, ICZA4) with D-π-A structural configuration incorporating indolo[3,2,1-jk]carbazole moiety as donor (D) unit, thiophene as π-linker and 2-cyanoacrylic acid as acceptor unit were investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT) methods. Indolo[3,2,1-jk]carbazole-based D-π-A dyes composed of different acceptor groups were designed. By modulating acceptor unit, the efficiency of D-π-A dye-based dye-sensitized solar cells (DSSCs) can be further improved. In the present work, four novel push-pull organic dyes only differing in electron acceptor, have been designed based on the experimental literature value of IC-2. In order to further improve the light harvesting capability of indolo[3,2,1-jk]carbazole dyes, the acceptor influence on the dye performance were examined. The NLO property of the designed dye molecules can be derived as polarizability and hyperpolarizability. The calculated value of ICZA2 dye is the best candidate for NLO properties. Furthermore, the designed organic dyes exhibit good photovoltaic performance of charge transfer characteristics, driving force of electron injection, dye regeneration, global reactivity, and light harvesting efficiency (LHE). From the calculated value of ICZA4 dye, it has been identified as a good candidate for DSSCs applications. Finally, it is concluded that the both ICZA2 and ICZA4 dyes theoretically agrees well with the experimental value of IC-2 dye. Hence, the dyes ICZA2 and ICZA4 can serve as an excellent electron withdrawing groups for NLO and DSSCs applications. 相似文献