摘要
本文用ＭＮＤＯ（ＲＨＦ，ＵＨＦ）方法计算了对苯醌和氢醌形成的分子络合物醌氨醌中的氢原子转移（双氢转移：Ｈ２Ｑ＋Ｑ＋Ｑ＋Ｈ２Ｑ；单氢转移：ＨＺＱ＋Ｑ→２ＨＱ），这些转移和电荷转移，生成热以及优化的转移中间态几何构型的关系，模型之一是：氢原子在平行的分子平面之间转移（ｐｐ）；模型之二是：氢原子通过氢键在同一平面内转移（ｚｚ）．单氢转移时（可能产生顺磁性），ＵＨＦ计算出（ｚｚ）方式的势垒比（ｐｐ）方式的高一倍．ＲＨＦ计算得出（ｐｐ）方式，在基态转移时的势垒比在激发态时高一倍．计算得出：（ｐｐ）方式转移时，醌和氢醌的二对氧原子的间距会协调地缩短，以配合氢原子的转移，而且，在基态作（ｐｐ）方式单氢原子转移的势垒比较小，这和晶态醌氢配在１００℃以上出现由抗磁性向顺磁性转变的现象是一致的．
Abstract The transfer of hydrogen atoms between molecules in the molecular complexesquinhydrone (Q-H_2Q) which consisted of benzoquinone(Q) and hydroquinone (H_2Q), is studiedwith MNDO(RHF, UHF). The first model (pp)is the hydrogen atoms transfers take place between the two parallel molecular planes; the second model(zz) is the transfers being through thehydrogen bond from H_2Q to Q which are keeping co-plane. The charge transfers, heat of formation and transicntstate configurations are optimized for two processes: (A). 2H-transfer:Q-H_2Q+Q→ Q+H_2Q, (B). 1H-transfer: H_2Q+Q→ 2HQ (semiquinone, have diamagneticparamagnetic). The 1H-transfer potential barrier of (zz) is 5.2eV(ground state) and 5.5eV (triplet); bat for (pp), it is 2.5 and 3.0 rcspechvely, the comparahvely lower barrier is the fact thatconsistent with phenomenon that crystal quinhydronc from diamagnetic converted toparamagnetic when temperature above 100℃. The barriers of 2H-transfer of (pp) in groundstate are 5.3eV(90°) and 7.9eV(112°), but in excited state they are 3.0eV(112°, singlet) and3.5eV(112°,triplct). The cooperation effects have been obtained by calculations; in (pp) model,when 1H-OR 2H-transfer from H_2Q to Q, the distances between the oxygen atoms canharmoniously shortened, then it is profit to the hydrogen transfer.
基金
中国科学技术大学基金
