Structures and spectral properties of iron(II), cobalt(II), and copper(II) complexes involving 2-(dimethylamino)-4(3H)-pteridinone

With a view to understanding the pterin cofactor-metal ion interactions, some divalent transition metal complexes containing 2-(dimethylamino)-4(3H)-pteridinone (NDMP), M(NDMP)(2)(CH3OH)(2) (M = Fe(II) (1), Co(II) (2), Cu(II) (3)) and Fe(NDMP)(2)Cl-2 (4), have been prepared and investigated by magnetic, spectroscopic, and X-ray diffraction methods. Complexes 1, 2, and 4 were found to be in a typical high-spin state, and complex 3 was found to be in a d(x2-y2) ground state. Complexes 1-3 were structurally determined. [Fe(NDMP)2(CH3OH)(2)]. 2CH(3)OH (1) crystallizes in the triclinic system, space group <P(1)over bar>, with a = 8.54(1) Angstrom, b = 9.353(10) Angstrom, c = 8.45(2) Angstrom, alpha = 96.5(1)degrees, beta = 98.3(2)degrees, gamma = 79.13(9)degrees, V = 653 Angstrom(3), and Z = 2. [Co(NDMP)(2)(CH3OH)(2)]. 2CH(3)OH (2) is isomorphous with 1 with a = 8.4753(6) Angstrom, b = 9.430(1) Angstrom, c = 8.3695(5) Angstrom, alpha = 95.885(7)degrees, beta = 98.412(6)degrees, gamma = 79.421(8)degrees, V = 648.48 Angstrom(3), and Z = 2. [Cu(NDMP)(2)(CH3OH)(2)] (3) crystallizes in the monoclinic system, space group P2(1)/a, with a = 8.428(1) Angstrom, b = 14.3857(8) Angstrom, c = 8.9570(8) Angstrom, beta = 95.225(8)degrees, V = 1081.5 Angstrom(3), and Z = 4. The final R and R-W values are 0.042 and 0.033 fbr 1, 0.056 and 0.040 for 2, and 0.040 and 0.018 for 3, respectively. The geometries around the metal ions are essentially the same, and each metal ion is octahedrally coordinated with 4-carbonyl oxygens and fi-nitrogens of NDMP molecules in the equatorial positions and two methanol molecules in the axial positions. The Fe(II) complexes 1 and 4 exhibited an absorption band centered at 568 nm (epsilon = 1900 M-1 cm(-1)) in DMF and a peak at 674 nm in the reflectance spectrum, respectively, both of which are assigned to a charge transfer. This and other spectroscopic and structural properties have been comparatively discussed.