New mononuclear, cyclic tetranuclear, and 1-D helical-chain Cu(II) complexes formed by metal-assisted hydrolysis of 3,6-di-2-pyridyl-1,2,4,5-tetrazine (DPTZ): Crystal structures and magnetic properties

The reactions of 3,6-di-2-pyridyl-1,2,4,5-tetrazine (DPTZ) with different Cu-II salts generate two new ligands, 2,5-bis(2-pyridyl)-1,3,4-oxodiazole (L-1) and N,N'-bis(alpha-hydroxyl-2-pyridyl)ketazine (H2L2), from the metal-assisted hydrolysis of DPTZ, and form three new complexes: a mononuclear complex [Cu(L-1)(2)(H2O)(2)].2ClO(4) (1), a linear coordination polymer [Cu(L-1)(NO3)(2)](8) (2), and a cyclic tetranuclear complex [Cu-4(L-2)(2)(Im)(2)(NO3)(4)(H2O)(2)] (3) (Im = imidazole). Crystal data for 1: space group P2(1)/n with a = 10.339(3) Angstrom, b = 10.974(2) Angstrom, c = 13.618(4) Angstrom, beta = 103.24(1)degrees, and Z = 2. Crystal data for 2: space group C2/c with a = 13.9299(14) Angstrom, b 9.2275(g) Angstrom, c 12.1865(13) Angstrom, beta = 111.248(2)degrees, and Z = 4. Crystal data for 3: space group P2(1)/n with a 9.3422(14) Angstrom, b 15.987(2) Angstrom, c 13.963(2) Angstrom, beta = 108.587(3)degrees, and Z = 2. L-1 acts as a bidentate chelating ligand in 1 and as a bis-bidentate chelating ligand in 2 with the shortest intramolecular (CuCu)-Cu-... distance of 6.093 Angstrom. L-2 is a hexacentate ligand to bridge four Cu-II ions, forming an interesting neutral cyclic tetranudear complex 3 with (CuCu)-Cu-... distances varying from 4.484 to 9.370 Angstrom. The mechanism of the metal assisted hydrolysis of DPTZ is discussed in detail. Magnetic susceptibility measurements indicate that 2 shows weak ferromagnetic interaction (J = 2.85 cm(-1)) along the 1-D helical chain, and that 3 displays weak antiferromagnetic interaction (J = -1.19 cm(-1) for the N-N bridge) and ferromagnetic interaction (j = 0.11 cm(-1) for the O-C=N bridge) between the adjacent Cu-II ions.