Theoretical insights into the magneto-structural correlation: Comparison between series of copper(I) and silver(I) metal complexes with nitronyl nitroxide radicals

Abstract

Using nitronyl nitroxide radicals, we presented a comparative study of magneto-structural correlations between series of CuI and AgI models (Cu(a) ∼ Cu(d) and Ag(a) ∼ Ag(d), modified from [CuI(immepy)2]PF6 and [AgI(impy)2]PF6 (Oshio et al., 1997). Cu(a) ∼ Cu(d) possess three characteristics that are significantly different from Ag(a) ∼ Ag(d) for the more utilization of CuI than that of AgI in the ferromagnetic joints of radical networks. (1) Structural shorter Cu-N length in Cu(a) ∼ Cu(d) than corresponding Ag-N length in Ag(a) ∼ Ag(d) leads to the quite larger Wiberg bond index (WBI), ∇2ρ(r) values, and metal atomic spin densities between triplet (T) and broken-symmetry (BS) states (ΔρT-BS) of the former than that of the latter. (2) From each of AgI (Ag(a) ∼ Ag(d)) to the corresponding one of CuI (Cu(a) ∼ Cu(d)), the spin density increases up to one or two order of magnitudes, which indicates the more notable spin delocalization from ONCN groups (paramagnetic centers) to CuI than that to AgI. Changing the dihedral angle (θ) between two radical components, the variation of the magnetic coupling constants (Jab) is directly proportional to the spin density of CuI but inversely proportional to that of one ONCN group. (3) Due to the larger d orbital distributions of CuI than that of AgI in the SOMOs, large metal-ligand charge transfer (MLCT) occurs in Cu(a) ∼ Cu(d) but little in Ag(a) ∼ Ag(d). The broken orthogonality is not evidently associated with the significantly different magnetic coupling interactions between CuI and AgI models.