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

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