CAJ | 학술논문

理论计算有助于复杂的有机和生物系统光谱的鉴定.对于核磁共振光谱,固体结晶中的化学位移和四极耦合常数(QCC)受到邻近的分子和晶格的氢键和范德华作用较大的影响,从而显示出与气态单体分子不同的NMR参数.因此,在固体晶体NMR参数的理论计算中有必要将氢键和范德华作用这两个因素考虑进来.基于周期性方法,本文采用L-Ala-Gly二肽和硝基苯晶体作为模型体系来考察该方法计算NMR参数的精度.研究结果显示周期结构模型能够将分子间的氢键和范德华作用考虑进来,得到的化学位移和QCC值明显优于传统的单分子模型和超分子模型得到的结果,采用该方法计算的结果能够重现NMR实验结果.
이론계산유조우복잡적유궤화생물계통광보적감정.대우핵자공진광보,고체결정중적화학위이화사겁우합상수(QCC)수도린근적분자화정격적경건화범덕화작용교대적영향,종이현시출여기태단체분자불동적NMR삼수.인차,재고체정체NMR삼수적이론계산중유필요장경건화범덕화작용저량개인소고필진래.기우주기성방법,본문채용L-Ala-Gly이태화초기분정체작위모형체계래고찰해방법계산NMR삼수적정도.연구결과현시주기결구모형능구장분자간적경건화범덕화작용고필진래,득도적화학위이화QCC치명현우우전통적단분자모형화초분자모형득도적결과,채용해방법계산적결과능구중현NMR실험결과.
Theoretical predictions are helpful for the spectroscopic identification of complicated organic and biological systems.For nuclear magnetic resonance (NMR) parameters,however,the chemical shift and quadrupole coupling constant (QCC) of the solid crystals are considerably affected by hydrogen bonding and van der Waals interactions from neighboring molecules and the crystal lattice leading to significant spectroscopic differences compared to isolated monomer molecules.Therefore,it is necessary to take these two factors into account for the precise predictions of chemical shifts and QCCs of solid crystals.L-alanylglycine dipeptide and nitrobenzene were selected as model crystals to demonstrate these effects.Here,the chemical shielding (CS) and QCC data were calculated based on the periodic structure model.The incorporation of intermolecular hydrogen bonding and crystal lattice effects by periodic models was found to be crucial in obtaining reliable predictions of CS and QCC values and rendering more explicit spectroscopic assignments for solid organic and biological systems.