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

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, μ 2 -SO 4 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 [Cu 2 (PAHAP)(NCS) 4 (DMF) 2 ]·2DMF ( 1 ) and [Cu 2 (PAHAP)(bipy) 2 (NO 3 ) 2 ](NO 3 ) 2 ·4H 2 O ( 2 ), and full structures are reported for [Cu 2 (PAHAP)(aln) 2 (H 2 O) 2 ](NO 3 ) 2 ·3H 2 O ( 3 ), [Cu 2 (PAHAP)(gly) 2 (NO 3 )(H 2 O)](NO 3 )·3H 2 O ( 4 ), [Cu 2 (PHMAP-H)(NO 3 ) 3 (H 2 O)(MeOH)] ( 6 ), [Cu 2 (PAHOX-H) 2 ](ClO 4 ) 2 ( 7 ), and [Cu(PAHOX)(SO 4 )] 2 ·2H 2 O ( 8 ). Complex 3 crystallized in the triclinic system, space group P 1̄ (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 P 1̄, 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 P 1̄, 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 C 2/ 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 P 2 1 / 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 (−2 J = 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 2 J 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 (2 J = 27 cm - 1 ).