Interpretation and Prediction of Properties of Transition Metal Coordination Compounds

Abstract

The discovery of transition metal complexes with novel properties is often based on serendipity, and the basis for the further development and optimization of such systems with specific properties is the careful analysis of experimental data. Important approaches in this process are classical methods derived from qualitative molecular orbital and ligand field theory, parameters related to donor-acceptor strengths, and concepts based on geometric and steric effects. The analysis of experimental data of novel systems, based on thorough electronic structure calculations, allows these novel systems to be interpreted and understood. As a result, new models and theories may emerge, possibly leading to rules on how the relevant properties of the new class of compounds may be further improved.There are also examples, where novel types of compounds or novel mechanistic ideas have emerged from theoretical studies; recent examples include the discovery of the first molecular Fe VI species [1], the experimental characterization of HgF 4 [2], the prediction and observation of multistate reactivity in iron-based oxygen activation [3,4], the discovery of an elusive, biologically relevant Cu-O 2 complex [5, 6], the investigation of copper-oxygen intermediates capable of hydroxylating arenes [7], and the search for the elusive high-spin Fe IV ¼O model system [8][9][10][11][12][13][14][15].Importantly, there is an increasing number of studies with a combination of preparative chemistry, the experimental investigation of molecular properties, theory, and modeling. In many areas, a thorough interpretation of experimental dataoften based on electronic structure calculations -has helped to create new models and rules, which then have inspired experimentalists to the synthesis and investigation of new compounds and reactions. The general approach described here, relies on the correlation of structures and properties, the possibility to enforce structures on transition metal centers by well-designed organic ligands and, specifically, a reliable structure prediction, leading to a combination of theory, structural modeling, and experiment [16,17].Modeling of Molecular Properties, First Edition. Edited by Peter Comba.

An Angular Overlap Model for Cu(II) Ion in the AMOEBA Polarizable Force Field

“…1-7 Being able to study these systems in silico can provide valuable insights to questions otherwise difficult to answer experimentally. 8,9 However, the quantum effects of d-shell have proved to be a challenge for computational models of TM ions. 10 Although TM ions can be treated as classical ions at long range, the local ligand field effect as a result of interactions between ligand and TM ion can dramatically affect the properties of TM complexes.…”

Insights into Excited State Intramolecular Proton Transfer: An Alternative Model for Excited State Proton Transfer of Green Fluorescence Protein

“…The Franck–Condon S 1 excited state to where electronic excitation takes place is described mostly by an excited Slater determinant where a molecular orbital (MO) 97–MO 98 excitation is considered. Hence, it is practically possible to understand the electronic structure of the Franck–Condon S 1 excited state at the MO level . Both MO 97 (highest occupied molecular orbital, HOMO) and MO 98 (lowest unoccupied molecular orbital, LUMO) are characterized by the uniform spread of electron density around the 4-benzylideneimidazolone moiety (Figure ), so the electronic vertical transition of o -TsABDI from its ground state (S 0 ) to its Franck–Condon S 1 excited state during electronic absorption does not involve CT (Scheme ).…”

“…The optimized S 1 excited state of the zwitterionic o -TsABDI from where fluorescence takes place is described mostly by an excited Slater determinant where an MO 97–MO 98 excitation is considered. Hence, it is practically possible to understand the electronic structure of the optimized S 1 excited state of the zwitterionic o -TsABDI at the MO level . Most of the electron density of the MO 98 is located on the π* orbital of the 4-benzylideneimidazolone moiety, while most of the electron density of the MO 97 is located on the n orbital of sulfonamide nitrogen (Figure ).…”

Automated Design of Realistic Organometallic Molecules from Fragments

“…Molecular mechanics, if properly trained and validated, can represent a good or even better compromise between accuracy and efficiency than DFT. 31,[199][200][201] In particular, while relative energies may not be accurate, 200,202 empirical force fields are particularly useful when conformational search is required. 201,203 Nevertheless, the varied chemistry of transition metals involves a wider range of coordination numbers and geometries than organic chemistry.…”