First Principles Investigation of Electronic Structure, Ligand Field and Magnetism of Re(III) Compounds
摘要
Transition metal complexes are widely used in the industry as catalysts and dyes. Predicting their properties includes calculating low-lying energy states, which is computationally intensive. Hence, we aim to provide a simple ligand field model of two Re(III) molecules, [ReCl \(_{6}\) ] \(^{3-}\) and ReCl \(_{3}\) (tppz) to accurately predict its low-lying energy states. Ab initio calculations were done with CASSCF and CASPT2. Two different model Hamiltonians were constructed with five different ligand field parameters: energy gap (J), spin-orbit coupling ( \(\lambda \) ), axial ( \(\varDelta \) ), and rhombic distortion ( \(\epsilon \) ), and orbital reduction factor ( \(\kappa \) ). A nine-by-nine matrix for the \(^{3}T_{1}\) configuration, and a fifteen-by-fifteen matrix for the \(t_{2g}^{4}\) configuration were obtained. The eigenvalues of the Hamiltonian were then fitted to the calculated energy states using a minimization function. The values for the \(^{3}T_{1}\) model fit extremely well, whereas the \(t_{2g}^{4}\) model has standard deviations ranging from 13 to 192. We obtained parameter values matching our predictions. The value of \(\lambda \) and \(\epsilon \) are close to 0 for [ReCl \(_{6}\) ] \(^{3-}\) , representing a perfect octahedral compound, and large for ReCl \(_{3}\) (tppz), which is not a perfect octahedral and will have some axial and rhombic splitting. We can expand our research by fitting the five parameters to other 5d \(^4\) transition metal complexes and including more states in the Hamiltonian.