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采用密度泛函B3LYP在6-31G*基组下,对有机显色剂1-(4-硝基苯基)-3-(5,6-二甲基-1,2,4三氮唑)-三氮烯(NPDMTT)的各种可能结构进行质子迁移的3种可能途径:(a)分子内质子迁移,(b)水助质子迁移,(c)甲醇助质子转移的计算,得到了各种途径异构体的相对能,获得了它们的互变异构过程的活化能、活化吉布斯自由能和质子转移反应的速率常数等性质。计算结果表明,分子内质子转移形成的各种异构体相对能量较大,当水分子或甲醇分子参与反应时,异构体的相对能量明显减小,但无论是孤立分子、一水合物还是一甲醇合物,其最稳定的异构体都相同,均为A2。溶剂化效应对异构化能垒的影响较大。最稳定的异构体分子内质子转移在N11和N13间转移的速控步骤的活化能为130.9 kJ.mol-1,反应速度常数为2.172×10-11s-1;当水分子参与反应以双质子转移机理异构化时,活化能显著降低,有利于三氮异构化,其中异构体质子在N11和N13间转移的速控步骤的活化能为22.55 kJ.mol-1,反应速度常数为3.617×107s-1;当醇分子参与反应以双质子转移机理异构时,活化能减小得更多,其中异构体质子在N11和N13间转移的速控步骤的活化能为2.384 kJ.mol-1,反应速度常数为9.032×1011s-1。计算结果还表明,氢键作用在增大NPDMTT一水合物和NPDMTT一甲醇合物相对稳定性、降低质子转移异构化反应活化能等方面起着重要作用。
Under the 6-31G * basis set using density functional theory B3LYP, the organic color reagent 1- (4-nitrophenyl) -3- (5,6-dimethyl-1,2,4 triazole) (A) intramolecular proton migration, (b) water-assisted proton migration, (c) methanol-proton transfer calculations have been obtained for each of the possible structures of triazine (NPDMTT) The relative energy of the pathway isomers, the activation energy of their tautomerization process, the rate constant of activation Gibbs free energy and proton transfer reaction were obtained. The calculated results show that the relative energies of the various isomers formed by intramolecular proton transfer are relatively large, and the relative energies of the isomers are significantly reduced when the water molecules or the methanol molecules are involved in the reaction. However, whether the isolated molecule or the monohydrate is Monomethanol, the most stable isomers are the same, are A2. The effect of solvation on the isomerization barrier is greater. The activation energy of the most stable isomer intramolecular proton transfer in the step-by-step transfer of N11 and N13 is 130.9 kJ · mol-1 and the reaction rate constant is 2.172 × 10-11s-1. When the water molecule participates in the reaction of bis When the proton transfer mechanism isomerization, the activation energy is significantly reduced, which is in favor of tri-isomerization. The activation energy of the isokinetic step in the transfer of the isomeric protons between N11 and N13 is 22.55 kJ · mol-1, the reaction rate constant Was 3.617 × 107s-1. The activation energy decreased more when the alcohol molecule was involved in the bipyramidal mechanism isomerization, and the activation energy of the isokinetic step in the transfer of the isomeric protons between N11 and N13 was 2.384 kJ mol-1, the reaction rate constant is 9.032 × 1011s-1. The calculated results also show that the hydrogen bonding plays an important role in increasing the relative stability of NPDMTT monohydrate and NPDMTT monomethanol and reducing the activation energy of proton transfer isomerization reaction.