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Structural and Magnetic Properties of Dicopper(II) Complexes of Polydentate Diazine Ligands

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journal contribution
posted on 30.05.1998 by Laurence K. Thompson, Zhiqiang Xu, Andrés E. Goeta, Judith A. K. Howard, Howard J. Clase, David O. Miller
A series of dinuclear copper(II) complexes of three polydentate diazine ligands (PAHAP, PHMAP, and PAHOX) is reported. The PAHAP and PHMAP complexes involve tetradentate ligand coordination with an N−N bridge between the metal centers. For PAHOX, one case involves oxime (N−O) bridges, while, in another, μ2-SO4 bridges are present. Free rotation of the copper magnetic planes around the N−N bond occurs for the PAHAP complexes and is influenced by secondary ligand steric effects (cis), but, for PHMAP, additional coordination fixes the complex in a trans configuration. Preliminary structures are reported for [Cu2(PAHAP)(NCS)4(DMF)2]·2DMF (1) and [Cu2(PAHAP)(bipy)2(NO3)2](NO3)2·4H2O (2), and full structures are reported for [Cu2(PAHAP)(aln)2(H2O)2](NO3)2·3H2O (3), [Cu2(PAHAP)(gly)2(NO3)(H2O)](NO3)·3H2O (4), [Cu2(PHMAP-H)(NO3)3(H2O)(MeOH)] (6), [Cu2(PAHOX-H)2](ClO4)2 (7), and [Cu(PAHOX)(SO4)]2·2H2O (8). Complex 3 crystallized in the triclinic system, space group P1̄ (No. 2), with a = 17.503(4) Å, b = 18.378(4) Å, c = 10.742(4) Å, α = 93.44(3)°, β = 93.19(3)°, γ = 62.98(2)°, and Z = 4. Complex 4 crystallized in the triclinic system, space group P1̄, with a = 11.506(12) Å, b = 12.525(18) Å, c = 10.319(4) Å, α = 94.47(7)°, β = 106.58(5)°, γ = 114.55(9)°, and Z = 2. Complex 6 crystallized in the triclinic system, space group P1̄, with a = 7.4754(1) Å, b = 8.7430(1) Å, c = 17.9942(2) Å, α = 84.690(1)°, β = 83.190(1)°, γ = 66.885(1)°, and Z = 2. Complex 7 crystallized in the monoclinic system, space group C2/c, with a = 33.5849(6) Å, b = 7.6016(1) Å, c = 22.6654(3) Å, β = 106.949(1)°, and Z = 8. Complex 8 crystallized in the monoclinic system, space group P21/n, with a = 9.866(2) Å, b = 10.128(2) Å, c = 15.418(1) Å, β = 108.051(8)°, and Z = 4. Antiferromagnetic exchange for 1, 3, 4, and 6 (−2J = 51.1, 45.6, 1.5, and 208 cm-1, respectively) is consistent with the angle of rotation (α) of the copper magnetic planes about the N−N bond. A linear relationship is found between α and 2J for a combined series of nine related complexes over an angle range of 105°. An estimate of the inherent ferromagnetism in the system is obtained from magnetic measurements close to the calculated angle of accidental orthogonality (2J = 27 cm-1).

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