Synthesis, Crystal Structures and Magnetic Properties of Two Heterobridged μ-Phenoxo-μ1,1-Azide/Isocyanate Dinickel(II) Compounds: Experimental and Theoretical Exploration

This investigation deals with the syntheses, crystal structures and experimental and density functional theoretical magnetic properties of two heterobridged and isomorphous mu-phenoxo-mu(1,1)-azide/isocyanate dinickel(II) compounds of composition [Ni-2(II)(L)(2)(mu(1,1)-N-3)(CH3CN)(CH3OH)](ClO4)center dot CH3CN (1) and [Ni-2(II)(L)(2)(mu(1,1)-NCO)(CH3CN)(CH3OH)](ClO4)center dot CH3CN (2), where HL is the 1:1 condensation product of 3-ethoxysalicylaldehyde and 4-(2-aminoethyl)-morpholine. The two compounds are isostructural as well, except that 1 contains end-on azide and 2 contains end-on isocyanate. One metal ion is surrounded by O(mu-phenoxo), N(mu(1,1)-azide/mu(1,1)-isocyanate), N(imine), N(amine), O(ethoxy) and O(phenoxide, monodentate) atoms, while the second metal ion is surrounded by O(mu-phenoxo), N(mu(1,1)-azide/mu(1,1)-isocyanate), N(imine), N(amine), O(methanol) and N(acetonitrile) atoms. Variable-temperature (2-300 K) magnetic susceptibility and variable-field (up to 5 T) magnetization data reveal ferromagnetic exchange interaction with J = 18.0 cm(-1) for 1 and J = 11.4 cm(-1) for 2. Broken symmetry density functional calculations of exchange interaction have been performed on both complexes and the DFT-computed J values are nicely matched with the experimental J values [J(exp) = 18.0 cm(-1) and J(DFT) = 17.2 cm(-1) for 1; J(exp) = 11.4 cm(-1) and J(DFT) = 8.9 cm(-1) for 2]. The magnetic properties have been nicely rationalized in terms of spin density, magnetic orbitals and breakdown approach.