Electronic reorganization: origin of sigma trans promotion effect.

摘要: Binding of two ligands trans to each other by some transition metal complexes may be cooperative [Khoroshun et al., Mol Phys 2002, 100, 523]. Several interesting consequent effects include (i) inverse relationship between bond strength and binding affinity; (ii) smaller coordination barriers formation weaker bonds; (iii) enhancement Lewis acidity with increased number ligands. We describe a simple model, σ promotion effect (TPE), which considers electronic reorganization structures, predicts the above-mentioned effects. The applied result present study is unified perspective on several facts heme chemistry. Particularly, we reiterate an important but often overlooked notion, developed previously within spin pairing model [Drago Corden, Acc Chem Res 1980, 13, 353], that, in hemoproteins, proximal histidine distal ligand such as O2 or CO cooperate promoting reorganization. As result, depopulation d orbital upon contributes phenomenon hemoglobin cooperativity. presented density functional (B3LYP) calculations realistic models, processes carbon monoxide Fe(II) porphyrins dinitrogen triamido/triamidoamine Mo(III) complexes, particularly evaluation due spin-state change location minima seams crossing, support TPE predictions. From broader theoretical perspective, would hopefully stimulate development much needed frameworks tools for facile comparisons wave functions their properties different geometries, species, states. Advancement practical function yield fresh qualitative perspectives chemical reactivity, promote better understanding related concepts © 2006 Wiley Periodicals, Inc. J Comput 28: 423–441, 2007