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).