Transition metal complexes with heteroscorpionate chelates, which are tridendate chelates where one of the three N-donor groups is unique, can exhibit temperature-dependent magnetism due to spin-crossover (SCO) behavior. This “on and off” magnetism may be useful in developing tunable nanoscale materials. However, not all transition metal heteroscorpionate complexes exhibit temperature-dependent magnetism. In order to predict SCO behavior of this class of complexes, we use density functional theory (DFT) to compare the electronic structure of MII(Tp’)2 complexes, where M = Fe, Co, Ni, and Zn and Tp’ is a heteroscorpionate chelate with two 3,5-dimethylpyrazole and one 1,2,3-benzotriazole N-donor rings. DFT functionals and basis sets are validated against experimental crystal structures and ΔHSCO values for FeII(Tp’)2. DFT predicts that the high-spin state of FeII(Tp’)2 is hyperopenshell, which indicates a multiconfigurational wavefunction. Natural bond order (NBO) analysis is used to compare metal-N bond order in relevant spin states of MII(Tp’)2 complexes and the gauge-independent atomic orbital method is used to compute NMR shielding tensors. Results are compared to experimental data to identify key characteristics of transition metal heteroscorpionate complexes that exhibit spin-crossover behavior and explain their predictable 11B NMR shifts.

Predicting spin-crossover behavior in transition metal heteroscorpionate complexes

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.