Ab Initio Studies on the Photophysics of Uric Acid and Its Monohydrates : Role of the Water Molecule
Ab Initio Studies on the Photophysics of Uric Acid and Its Monohydrates : Role of the Water Molecule
复制标题
尿酸及其一水合物光物理学的从头算研究：水分子的作用
DOI：
10.1021/jp411880z
复制
发表时间：
2014
期刊：
影响因子：
2.9
通讯作者：
T. Taketsugu
中科院分区：
文献类型：
--
作者：
S. Yamazaki;S. Urashima;H. Saigusa;T. Taketsugu
采用从头算方法，对尿酸的三种最低能量互变异构体和尿酸一水合物的七种最稳定异构体的热力学行为进行了全面的研究。基态能量的CCSD（T）方法计算，而激发能和电离能以及激发态势能曲线的光诱导过程中的CC2方法计算。对于1 ππ* 态，当水分子与特定的羰基发生氢键时，一水分子簇的激发能明显低于尿酸的激发能.计算的激发态势能曲线表明，某些一水合物异构体可以在1 ππ* 态下发生水分子从一个位置向另一个位置的迁移，其能垒很小。对于尿酸及其一水合物，在较高的激发能下，可能发生1 πσ* 态NH键离解的非辐射衰变。计算结果的基础上，尿酸一水合物的共振双光子电离光谱的具体异构体的情况下，可能的机制进行了讨论。
The photophysical behavior of three lowest-energy tautomers of uric acid and seven most stable isomers of uric acid monohydrate is comprehensively studied by ab initio calculations. Ground-state energies are calculated with the CCSD(T) method, while excitation and ionization energies as well as excited-state potential energy profiles of photoinduced processes are calculated with the CC2 method. For the1ππ* state, it is found that the excitation energy of the monohydrate cluster is significantly lower than that of isolated uric acid when the water molecule is hydrogen-bonded at a specific carbonyl group. The calculated excited-state potential energy profiles suggest that some monohydrate isomers can undergo a migration of the water molecule from one site to another site in the1ππ* state with a small energy barrier. It is also found for both uric acid and its monohydrate that nonradiative decay via the NH bond dissociation in the1πσ* state is likely to occur at higher excitation energies. On the basis of the computational results, possible mechanisms for the absence of specific isomers of uric acid monohydrate from the resonant two-photon ionization spectrum are discussed.