The magneto-structural correlation between a Mn(II) ion, coordinated in an octahe-dral environment, and two nitronyl nitroxide radical ligands in trans- and cis-metal-radical com-plexes is investigated by the broken s...The magneto-structural correlation between a Mn(II) ion, coordinated in an octahe-dral environment, and two nitronyl nitroxide radical ligands in trans- and cis-metal-radical com-plexes is investigated by the broken symmetry (BS) approach within density functional theory (DFT). The dependences of coupling constants J on three structural parameters: (i) bond angle θ (Mn-O-N (nitroxide)); (ii) rotating angle ψ, defined by the nitronyl nitroxide radical plane rotating around the axial Mn-O (nitroxide); (iii) bond distance R (Mn-O (nitroxide)) are directly calculated. Our calculations showed that both trans- and cis-Mn(II)-radical complexes behave a stronger antiferromagnetic interaction, consistent with experiments. In view of molecular orbital theory, the direct exchanges, including σ-type and π-type exchanges, are responsible for the magnetic ex-change pathways. There is a preferable linear correlation between the calculated coupling con-stants J and the overlap integral squares Sa2b between the local magnetic orbitals at the various rotating angle ψ at the fixed bond angle θ and bond distance R, in both trans- and cis-Mn(II)- radical complexes.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.20273005,20490210,NSFC/RGC 20318001)the Doctoral Program Foundation of the Ministry of Education(Grant No.20030001066).
文摘The magneto-structural correlation between a Mn(II) ion, coordinated in an octahe-dral environment, and two nitronyl nitroxide radical ligands in trans- and cis-metal-radical com-plexes is investigated by the broken symmetry (BS) approach within density functional theory (DFT). The dependences of coupling constants J on three structural parameters: (i) bond angle θ (Mn-O-N (nitroxide)); (ii) rotating angle ψ, defined by the nitronyl nitroxide radical plane rotating around the axial Mn-O (nitroxide); (iii) bond distance R (Mn-O (nitroxide)) are directly calculated. Our calculations showed that both trans- and cis-Mn(II)-radical complexes behave a stronger antiferromagnetic interaction, consistent with experiments. In view of molecular orbital theory, the direct exchanges, including σ-type and π-type exchanges, are responsible for the magnetic ex-change pathways. There is a preferable linear correlation between the calculated coupling con-stants J and the overlap integral squares Sa2b between the local magnetic orbitals at the various rotating angle ψ at the fixed bond angle θ and bond distance R, in both trans- and cis-Mn(II)- radical complexes.
