The crystal and molecular structures of bis(2,2-bis(5-phenyl-2-imidazolyl)propane)copper(II) diperchlorate tetramethanolate (1) and bis(l,3-bis(5-phenyl-2-imidazolyl)-2-thiopropane)copper(II) diperchlorate pentamethanolate (2) have been determined from single-crystal, three-dimensional X-ray data collected by counter methods. Complex 1 crystallized from CH3OH as light brown prisms in space group PI with Z = 1, a = 11.064 (5) Å, b = 13.469 (7) Å, c = 9.018 (3) Å, a = 105.85 (4)°, β = 104.85 (4)°, = 85.58 (4)°, dcalcd = 1.393 g/cm3, and dobsd = 1.43 (5) g/cm3. Least-squares refinement of 2411 reflections having Fo 2 > 3σ(Fo 2) gave a conventional R factor of 0.064. The structure contains discrete Cu(II) monomers having planar N4 ligand donor sets with Cu-N bond distances of 1.979 (5) and 1.960 (4) Å. The ClO4 - and CH3OH groups are lattice species well removed from the copper atoms. Complex 2 crystallized from CH3OH as orange-brown prisms in space group P21/c with Z = 2, a = 12.08 (2) Å, b = 11.98 (2) Å, c = 18.93 (3) Å, β = 96.19 (4)°, dcalcd = 1.360 g/cm3, and dobsd = 1.43 (5) g/cm3. Least-squares refinement of 2351 reflections having Fo 2 > 3σ(Fo 2) gave a conventional R factor of 0.089. The structure contains discrete Cu(II) monomers having tetragonal N4S2 ligand donor sets with equatorial Cu-N bond distances of 2.020 (9) and 2.019 (7) Å and apical Cu-S bond distances of 2.824 (5) Å. Electronic and ESR spectra are reported for 1 and 2. Electronic spectra also are reported for bis(1,2-bis(5-phenyl-2-imidazolyl)ethane)copper(II) diperchlorate (3) and bis(1,3-bis(5-tert-butyl-2-imidazolyl)-2-thiopropane)copper(lI) diperchlorate (4). In contrast to the prominant (c > 1000) ligand to metal charge-transfer (LMCT) absorption at ~25 000 cm-1 exhibited by equatorial thioether-Cu(II) units (Cu-S = ~2.3 Å), the corresponding absorptions anticipated for complexes 2 and 4 were too weak to detect. Complexes 1-4 all exhibit a weak (ε = 200) absorption at ~25000 cm-1 attributable to poorly resolved π(imidazole) → Cu(II) LMCT. The assignments of thioether → Cu(II) LMCT proposed for plastocyanin and other type 1 copper proteins are reconsidered in view of the above spectroscopic results and the available protein crystallographic data.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry