Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060 Kraków, Poland.
J Phys Chem B. 2010 Jan 28;114(3):1518-28. doi: 10.1021/jp910220r.
The multiconfigurational CASSCF/CASPT2 approach, along with various functionals of density functional theory, is applied to selected iron(II)-nitrosyl ({FeNO}(7)) complexes, both with heme and nonheme groups. The energetics of the lowest doublet and quartet spin states at the correlated ab initio (CASPT2) level is presented for the first time. Comparison of the CASSCF and (unrestricted) DFT spin densities indicates that the nonhybrid functionals yield the spin densities most closely to the ab initio ones. The analysis of the multiconfigurational CASSCF wave function in terms of the localized active orbitals allows one to resolve the nature of Fe-NO bonding as a mixture of Fe(II)-NO(0) and Fe(III)-NO(-) resonance structures (in comparable contributions) for both spin states and various ligands.
本文采用多组态 CASSCF/CASPT2 方法和各种密度泛函理论泛函，对具有血红素和非血红素基团的选定的铁(II)-亚硝酰基({FeNO}(7))配合物进行了研究。首次在相关从头算（CASPT2）水平上呈现了最低双重态和四重态自旋态的能量。CASSCF 和（非限制）DFT 自旋密度的比较表明，非混合泛函产生的自旋密度最接近从头算的自旋密度。根据局域活性轨道对多组态 CASSCF 波函数进行分析，使得人们能够解析 Fe-NO 键的性质，两种自旋态和各种配体的 Fe(II)-NO(0)和 Fe(III)-NO(-)共振结构（以相当的贡献混合存在）。
