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Theoretical Study of Remote Substituent Effects on X-H (X=CH2, NH,O) Bond Dissociation Energies of Azulene 总被引:1,自引:0,他引:1
In the study, the X-H (X=CH2, NH, O) bond dissociation energies (BDE) of para-substituted azulene (Y-C10H8X-H) were predicted theoretically for the first time using Density Functronal Theory (DFT) methods at UB3LYP/6-311 + +g(2df,2p)//UB3LYP/6-31 +g(d) level. It was found that the substituents exerted similar effects on the X-H BDE of azulene as those on benzene, except for 6-substituted 2-methylazulene. Owing to the substituent-dipole interaction, the reaction constants (ρ^+) of 2- and 6-Y-CIoHsX-H (X=NH and O only) varied violently. The origin of the substituent effects on the X-H BDE of azulene was found, by both GE/RE and SIE theory, to be directly associated with variation of the radical effects, although the ground effects also played a modest role in determining the net. substituent effects. 相似文献
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通过荧光猝灭实验和测定二聚体裂解程度的辐照实验,研究色氨酸(Trp)及 其二肽色氨酰苯丙氨酸(Trp-Phe)对cis-syn型1,3-二甲基胸腺嘧啶二聚体( DMTD)的光敏化裂解作用。结果表明,色氨酸及其二肽在较强光(λ > 290 nm) 辐照下,主要通过双光子电离生成的光合电子(e_(aq)~-)导致二聚体裂解,其次 ,通过激发单重态与二聚体间的电子转移导致二聚体裂解。另外一导致二聚体裂解 的可能途径:色氨酸残基激发三重态与二聚体间的电子转移光敏化二聚体裂解。 相似文献
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The exact structure of an arginine-carboxylate salt bridge in different chemical environments remains a controversial problem.In the present work,the zwitterionic and neutral forms of arginine-carboxylate salt bridge were studied by the B3LYP/6-311G(d,p)//PM3 method.It turns out that the neutral forms are more stable than the zwitterionic coumterparts in gas phase.However,whnen bound by α-cyclodextrin,the zwitterionic forms become more stable than the corresponding neutral ones.It is suggested that the hydrophobic environment provided by the cyclodextrin cavity leads to such behavior.Therefore,the salt bridge still could be in a zwitterionic form in the hydrophobic interior of the real proteins. 相似文献
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合成了一系列的N-10位取代的吩噻嗪给体受体化合物,这些受体包括苯、苯甲醚、吡啶、萘、苯乙酮和苯乙腈.研究了不同极性溶剂中这些化合物的分子内的光诱导电荷转移现象.稳态荧光的溶剂化效应和较大的Stokes位移清楚表明,仅仅后四种吩噻嗪衍生物的激发态存在着分子内的电荷转移,而苯和苯甲醚取代吩噻嗪因为受体部分氧化电势低,所以不具有这种特性.修正过的Lippert-Mataga公式被用来分析Stokes位移值,从而获得激发态偶极矩.较大的激发态偶极矩说明在激发态时这四种给体受体化合物体系内发生了完全的电子转移.氧化还原电势的数据表明基态时这四种衍生物给体受体部分的作用比较弱.分析荧光光谱获得的结果说明伴随着电荷转移这四种衍生物的激发态构型变化比较小,给体和受体间的扭转角在电荷转移后的激发态与在基态时相似. 相似文献
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