Microscopic origins of the ferromagnetic exchange coupling in oxoverdazyl-based Cu(II) complex

摘要

The exchange channels governing the experimentally reported coupling constant Jexpt=6 cm−1 value in the verdazyl-ligand based Cu II complex Cu hfac 2 imvdz are inspected using wavefunction-based difference dedicated configuration interaction calculations. The interaction betweenthe two spin 1/2 holders is summed up in a unique coupling constant J. Nevertheless, by graduallyincreasing the level of calculation, different mechanisms of interaction are turned on step by step.In the present system, the calculated exchange interaction then appears alternatively ferromagnetic/antiferromagnetic/ferromagnetic. Our analysis demonstrates the tremendously importance of somespecific exchange mechanisms. It is actually shown that both parts of the imvdz ligandsimultaneously influence the ferromagnetic behavior which ultimately reaches Jcalc=6.3 cm−1, invery good agreement with the experimental value. In accordance with the alternation of J, it isshown that the nature of the magnetic behavior results from competing channels. First, anantiferromagnetic contribution can be essentially attributed to single excitations involving the network localized on the verdazyl part. In contrast, the ligand-to-metal charge transfer LMCT involving the imidazole moiety affords a ferromagnetic contribution. The distinct nature / of themechanisms is responsible for the net ferromagnetic behavior. The intuitively innocent part of theverdazyl-based ligands is deeply reconsidered and opens new routes into the rational design ofmagnetic objects