S-酮洛芬电子结构及手性光谱性质的理论研究

Theoretical study on electronic structures and chirospectra of S-ketoprofen

采用DFT及TD-DFT方法在B3LYP/6-311++G**水平对S-酮洛芬电子结构及手性光学性质进行了理论研究.研究发现,羰基与两个苯环发生共轭;由于C(20)与C(11)上H原子之间存在空间位阻,羰基与环A及环B之间均存在一定的二面角.VCD谱中,标题化合物在1216和1712 cm^(-1)处存在负性康登效应;在733、1803、1465和3751 cm^(-1)处存在正性康登效应.C(14)=O(21)和C(4)=O(5)伸缩振动的空间方向相反,在VCD谱上的康登效应符号也刚好相反.甲醇溶液中,S-酮洛芬在214、334 nm处存在负性康登效应,在226、274 nm处存在正性康登效应.214和226 nm、274和334 nm处的电子转移方向分别相反,在ECD谱上呈现出符号相反的康登效应.

The electronic structures of S-ketoprofen （S-KT） and chirospectra were calculated by using density functional theory （DFT） and time-dependent density function theory （TD-DFT） at the B3LYP/6-311＋＋G＊＊ level. The calculation results demonstrate that the conjugated effect is observed between C（24）=O（21） and two benzene rings, but dihedral angles are formed because of the steric effect of H atoms bonded with C（20） and C（11）. Detailed analyses of Vibrational Circular Dichroism （VCD） spectra reveals that negative Cotton effects could be observed at 1216 and 1712 cm-1, and positive Cotton effects could be appeared at 733、1803、1465 and 3751 cm-1. Opposite Cotton effects produced at 1712 and 1803 nm may due to the contrary vibration direction of C（14）=O（21） and C（4）=O（5）. In methanol, Electronic Circular Dichroism （ECD） of S-KT has negative Cotton effects at 214 and 334 nm and positive Cotton effects at 226 and 274 nm. Opposite Cotton effects at 214 and 226 nm is also found, because the direction of intramolecular electron transfer is opposite. A similar case is exist at 274 and 234 nm.