Preparation and Characterization of [rac-5, 7, 7, 12, 14, 14, -Hexamethyl-1, 4, 8, 11-Tetraazocyclotetradecane]Copper(II) o-Mercaptobenzoate Hydrate, [Cu(tet b)(o-SC₆H₄CO₂)].H₂O, a Complex with a CuN₄S (Mercaptide) Chromophore

The synthesis, crystal structure, electronic spectra, magnetic susceptibility, and ESR data are reported for the title complex. Dark green crystals were obtained in the monoclinic space group P2_1/n with a = 8.387 (3) Å, b = 21.16 (1) Å, c =14.677 (5) Å, β = 90.92 (3)°, _d0bsd = 1.32 (1) g/cm³, d_Calcd = 1.322 g/cm³, Z = 4. Least-squares refinement of 1870 reflections having F2 ≥ 2σ gave a conventional R factor of 0.079 and R_wF = 0.095. The structure consists of Cu(II) monomers with distorted trigonal bipyramidal N₄S ligand donor sets. Structural parameters within the triangular fragment include Cu-S, 2.359 (4) Å Cu-N, 2.193 (10) and 2.132 (9) Å S-Cu-N, 120.8 (3) and 135.4 (3)° and N-Cu-N, 103.5 (4)°. The coordination geometry is completed by two apical Cu-N bonds (2.028 (9), 1.997 (10) Å). Both the X-band ESR spectra (g1 = 2.074, g2 = 2.086 (poorly resolved), g3 = 2.117) and the measured magnetic moment (2.02 (5) μ_B at 293 K) of the polycrystalline complex support its formulation as a Cu(II) N₄S(mercaptide) species. Structural and electronic-spectral data are compared with those reported for analogous CuN₄X (X = Cl, CN) species. The title complex exhibits absorptions at ~590 (poorly resolved), 730 (ε ~900), and ~920 nm (shoulder), which are assigned as ligand field transitions. Additional spectral features at 360, 418, and 430 nm which are not exhibited by either free -SC₆H₄CO₂-or a reference Zn(tet b)(o-^-SC₆H₄CO₂-)•H₂O complex are attributed to S → Cu(II) charge transfer.