MAGNETOSTRUCTURAL CORRELATIONS OF DIMERIC COPPER(II) TRICHLOROACETATES

Sixteen crystal structures of dimeric copper(II) trichloroacetates, (I)-(XVI), have been deter-mined by single-crystal X-ray diffraction. In crystals of the compounds which have small -2J values, less than 200 cm-1, the coordination geometry around the Cu atom is deformed from square pyramidal (SP) to trigonal bipyramidal (TBP), and the Cu...Cu interatomic distance is elongated. The longer the Cu...Cu distance, the smaller the -2J value, indicating that the spin super exchange interaction is weaker in the TBP than in the SP structure. The magnetic orbitals in the TBP structure may consist mainly of copper d(z2) orbitals (z along the axial direction of the TBP), which are perpendicular to each other at the two Cu atoms, and overlap only slightly with each other on the bridging carboxylate ligands. (I): Tetrakis(mu-trichloroacetato-O,O')-bis(2-ethylpyridine)dicopper(II), [Cu(C2Cl3O2)2C7H9N]2, -2J = 79 cm-1. (II); Tetrakis(mu-trichloroacetato-O,O')-bis(2,3-dimethylpyridine)dicopper(II) monotoluene solvate, [Cu-(C2Cl3O2)2C7H9N]2.C7H8, -2J = 95 cm-1. (III): Tetrakis(mu-trichloroacetato-O,O')-bis(2,5-dimethylpyridine) dicopper(II) monotoluene solvate, [Cu(C2Cl3O2)2C7H9N]2.C7H8, -2J = 102 cm-1. (IV): Tetrakis(mu-trichloroacetato-O,O')-bis(3,4-dimethylpyridine)dicopper(II), [Cu(C2Cl3O2)2C7H9N]2, -2J = 107 cm-1. (V): Tetrakis(mu-trichloroacetato-O,O')bis(2-chloro-5-nitropyridine(dicopper(II), [Cu(C2Cl3O2) 2C5H3ClN2O2]2, -2J = 131 cm-1. (VI): Tetrakis(mu-trichloroacetato-O,O')-bis(caffeine)dicopper(II), [Cu(C2Cl3O2)2C8H10N4O2]2, -2J = 136 cm-1. (VII): Tetrakis(mu-trichloroacetato-O,O')-bis(3-cyanopyridine) dicopper(II), [Cu(C2ClO2)2C6H4N2]2 -2J = 138 cm-1. (VIII): Tetrakis(mu-trichloroacetato-O, O')-bis(2,5-dichloropyridine)dicopper(II) monobenzene solvate, [Cu(C2Cl3O2)2C5H3Cl2N]2.C6H6, -2J = 141 cm-1. (IX): Tetrakis(mu-trichloroacetato-O,O')-bis(2,5-dichloropyridine)dicopper(II), [Cu(C2Cl3O2)2C5H3Cl2N]2 -2J = 191 cm-1. (X): Tetrakis(mu-trichloroacetato-O,O')-bis(3-chloropyridine)dicopper(II), [Cu(C2Cl3O2)2C5H4ClN]2, -2J = 193 cm-1. (XI): Tetrakis(mu-trichloroacetato-O,O')-caffeine)dicopper(II) ditoluene solvate, Cu2(C2Cl3O2)4C8H10N4O2].2C7H8, -2J = 220 cm-1. (XII): Tetrakis(mu-trichloroacetato-O,O')bis(4-cyanopyridine-dicopper(II), [Cu(C2Cl3O2)2C6H4N2]2, -2J = 229 cm-1. (XIII): Tetrakis(mu-trichloroacetato-O,O')bis(4,7-dichloroquinoline)dicopper(II) [Cu(C2Cl3O2)2C9H5Cl2N]2, -2J = 237 cm-1. (XIV): Tetrakis(mu-trichloroacetato-O,O')-bis(2-fluorobenzothiazole)dicopper(II), [Cu(C2Cl3O2)2C7H4FNS]2, -2J = 240 cm-1. (XV): Tetrakis(mu-trichloroacetato-O,O)-bis(3,5-dichloropyridine)dicopper(II) monotoluene solvate, [Cu(C2Cl3O2)2C5H3Cl2N]2.C7H8. (XVI): Tetrakis(mu-trichloroacetato-O,O')-bis(3,5-dimethylpyridine) dicopper(II) dibenzene solvate, [Cu(C2Cl3O2)2C7H9N]2.2C6H6. The -2J values of (XV) and (XVI) after removal of solvent molecules from the crystals are 92 and 74 cm-1, respectively.