含轴向咪唑配体的手性SalenCo(川)配合物ECD谱的理论解析  

Theoretical Analysis of the ECD Spectra of SalenCo(Ⅲ) Complexes Containing Axial Imidazole Ligands

作　　者：苏晓玲[1] 王越奎[1] 王炎[2] 贾杰[1] 高小丽[1] 

机构地区：[1]山西大学分子科学研究所,化学生物学与分子工程教育部重点实验室,太原030006 [2]吕梁学院化学化工系,山西吕梁033000

出　　处：《物理化学学报》2011年第7期1633-1639,共7页Acta Physico-Chimica Sinica

基　　金：国家自然科学基金(20673069);山西省自然科学基金(2007011021)资助项目~~

摘　　要：用密度泛函理论(DFT)方法,在B3LYP和混合基组(C,H原子用6-31 G*;Co,N,O用6-31 1+G(2d,p))水平上,对含轴向配体的三种Co(Ⅲ)席夫碱配合物[Co(MeO-salen)(国m)_2]^+、[Co(MeO-salen)(2-Melm)_2]^+和[Co(MeO-salen)(Melm)_2]^+(lm=咪唑,Melm=1-甲基咪唑,2-Melm=2-甲基咪唑,MeO-salenH2=salen型席夫碱,即(R,R)-N,N'-双(5-甲氧基亚水杨基)-1,2-二亚胺基环己烷)在二氯甲烷溶液中的基态结构进行了优化,并用含时密度泛函理论(TDDFT)方法,在相同泛函和基组水平上计算了其激发能、振子强度和旋转强度.这些计算中均用极化连续介质模型(PCM)考虑了溶剂效应.计算的电子圆二色(ECD)谱与实验谱吻合较好.通过对有关跃迁性质的分析,对实验电子圆二色光谱进行了解析与指认.结果表明,长波区的第一个园二色(CD)吸收带主要是由π→d荷移跃迁(LMCT)引起的,而不是通常认为的d→d跃迁.轴向配体的加入对配合物前两个CD吸收带的符号没有影响,但会影响带形和强度.手性salen配合物的绝对构型为λ(RR)时,第一个CD吸收带为正,第二个为负.这些结论对于深入理解该类配合物的电子结构和手征光学性质具有重要的科学意义.The geometries of the cobalt complexes [Co（MeO-salen）（Im）2]＋, [Co（MeO-salen）（2-Melm）2]＋, and [Co（MeO-salen）（Melm）2]＋ （Im=imidazole; Melm=l-methylimidazole, 2-Melm=2-methyiimidazole, MeO- salenH2=salen type Schiff base： （R,R）-N,N＇-bis（5-methoxy-salicylidene）-l,2-diiminocyclohexane） in dichloromethane solution were optimized using density functional theory （DFT） at the B3LYP level of theory with the mixed basis set： 6-31G＊ for C and H, and 6-311 ＋G（2d,p） for Co, N, and O atoms. Based on the optimized geometries the excitation energies, oscillator and rotational strengths, and the electronic circular dichroism （ECD） spectra of the complexes were calculated using time-dependent density functional theory （TDDFT） with the same functional and basis sets. In these calculations solvent effects were included using the polarized continuum model （PCM）. The calculated ECD spectra are in good agreement with the observed ones. Detailed analyses of the dominant transitions reveal that the first circular dichroism （CD） band in the long wavelength region is dominated by the ligand-to-metal charge transfer transition π→ d,which was wrongly assigned to a d→d transition in the literature. The introduction of imidazole ligands to the axial positions has no influence on the sign of the first two CD bands, but it does have a significant influence on the shape and intensity of the CD spectra. For complexes with the λ（RR） chiral configuration the first CD absorption band is positive and the second is negative. These findings provide a deep insight into the electronic structures and chiroptical properties of the chelates.

关 键 词：钴席夫碱配合物 轴向咪唑配体 圆二色谱 TDDFT计算 手征光学性质 

分 类 号：O621.13[理学—有机化学]