Tetranuclear Copper(II) and Nickel(II) Cluster Complexes Derived by Self-Assembly from a Series of Tetradentate Diazine Ligands: Structural and Magnetic Studies

A series of tetranuclear copper(II) and nickel(II) complexes is described, all of which form by a strict self-assembly process involving just a single ligand and the metal salt. The ligands POAP, POAPZ, PZOAP, and
6POAP contain terminal pyridine and pyrazine residues bound to a central flexible diazine subunit (N−N) and
contain two potentially bridging groups (alkoxo and diazine). In all cases but one the metals are linked by alkoxo
oxygens alone, forming essentially square [M4(μ2-O)4] clusters. A rectangular copper(II) complex [Cu4(μ2-N2)2(μ2-O)2] involves a mixture of two alkoxo and two diazine bridges. The square Cu4O4 clusters exhibit ferromagnetic
coupling between the metal centers, associated with the orthogonal arrangement of magnetic orbitals, while for
the Ni4O4 clusters the nickel(II) centers are coupled antiferromagnetically. The [Cu4(μ2-N2)2(μ2-O)2] cluster exhibits
strong antiferromagnetic coupling through a trans Cu(N-N)Cu bridging arrangement, typical for systems of this
sort. X-ray structures are reported for [Cu4 (POAP-H)4(H2O)2](NO3)4·4H2O (2), [Cu4(POAPZ-H)4(H2O)](NO3)4·3H2O (3), [Cu4(6POAP-H)4](ClO4)4 (4), [Cu4(PZOAP-H)4](NO3)4·3H2O (5), [Ni4(POAP-H)4 (H2O)4](NO3)4·8H2O
(6), and [Ni4(PZOAP-H)4(H2O)4](ClO4)4·5H2O (9). 2 crystallized in the monoclinic system, space group C2/c,
with a = 20.479(3) Å, b = 14.920(2) Å, c = 19.671(3) Å, β = 90.591(4)°, and Z = 8. 3 crystallized in the
monoclinic system, space group P21/c, with a = 14.12(1) Å, b = 14.116(3) Å, c = 29.043(4) Å, β = 94.50(3)°,
and Z = 4. 4 crystallized in the monoclinic system, space group C2/c, with a = 22.646(4) Å, b = 25.842(5) Å,
c = 12.349(5) Å, β = 110.34(2)°, and Z = 4. 5 crystallized in the monoclinic system, space group P2/n, with a
= 14.3573(4) Å, b = 10.8910(6) Å, c = 20.5360(10) Å, β = 96.975(4)°, and Z = 4. 6 crystallized in the triclinic
system, space group P1̄, with a = 12.0509(6) Å, b = 12.7498(6) Å, c = 23.1208 Å, α = 93.1050(10)°, β =
100.1500(10)°, γ = 108.5050(11)°, and Z = 2. 9 crystallized in the orthorhombic system, space group Pbcn, with
a = 14.368(4) Å, b = 25.469(7) Å, c = 18.479(5) Å, and Z = 4.

本文报道了一系列四核铜(II)与镍(II)配合物，所有配合物均通过仅涉及单一配体与金属盐的严格自组装过程生成。配体POAP、POAPZ、PZOAP及6POAP均带有末端吡啶与吡嗪残基，这些残基与中心柔性二嗪亚基（N−N）相连，且包含两个潜在桥联基团（烷氧基与二嗪）。除一例外，所有配合物中的金属离子仅通过烷氧基氧原子相连，形成近似正方形的[M4(μ2-O)4]簇合物。一例矩形铜(II)配合物[Cu4(μ2-N2)2(μ2-O)2]则同时采用两条烷氧基桥与两条二嗪桥进行连接。正方形Cu4O4簇合物的金属中心间存在铁磁耦合作用，该作用与磁轨道的正交排布相关；而Ni4O4簇合物中的镍(II)中心则表现为反铁磁耦合。该[Cu4(μ2-N2)2(μ2-O)2]簇合物通过反式Cu(N-N)Cu桥联结构表现出强反铁磁耦合，这是此类体系的典型特征。本文报道了以下配合物的X射线晶体结构：[Cu4(POAP-H)4(H2O)2](NO3)4·4H2O（2）、[Cu4(POAPZ-H)4(H2O)](NO3)4·3H2O（3）、[Cu4(6POAP-H)4](ClO4)4（4）、[Cu4(PZOAP-H)4](NO3)4·3H2O（5）、[Ni4(POAP-H)4(H2O)4](NO3)4·8H2O（6）以及[Ni4(PZOAP-H)4(H2O)4](ClO4)4·5H2O（9）。配合物2属单斜晶系，空间群为C2/c，晶胞参数：a=20.479(3) Å，b=14.920(2) Å，c=19.671(3) Å，β=90.591(4)°，Z=8。配合物3属单斜晶系，空间群为P21/c，晶胞参数：a=14.12(1) Å，b=14.116(3) Å，c=29.043(4) Å，β=94.50(3)°，Z=4。配合物4属单斜晶系，空间群为C2/c，晶胞参数：a=22.646(4) Å，b=25.842(5) Å，c=12.349(5) Å，β=110.34(2)°，Z=4。配合物5属单斜晶系，空间群为P2/n，晶胞参数：a=14.3573(4) Å，b=10.8910(6) Å，c=20.5360(10) Å，β=96.975(4)°，Z=4。配合物6属三斜晶系，空间群为P1̄，晶胞参数：a=12.0509(6) Å，b=12.7498(6) Å，c=23.1208 Å，α=93.1050(10)°，β=100.1500(10)°，γ=108.5050(11)°，Z=2。配合物9属正交晶系，空间群为Pbcn，晶胞参数：a=14.368(4) Å，b=25.469(7) Å，c=18.479(5) Å，Z=4。