Loops, Chains, Sheets, and Networks from Variable Coordination of Cu(hfac)2 with a Flexibly Hinged Aminoxyl Radical Ligand

One pair of reactants, Cu(hfac)2 = M and the hinge-flexible radical ligand 5-(3-N-tert-butyl-N-aminoxylphenyl)pyrimidine (3PPN = L), yields a diverse set of five coordination complexes: a cyclic loop M2L2 dimer; a 1:1 cocrystal between an M2L2 loop and an ML2 fragment; a 1D chain of M2L2 loops linked by M; two 2D M3L2 networks of (M–L)n chains cross-linked by M with different repeat length pitches; a 3D M3L2 network of M2L2 loops cross-linking (M–L)n-type chains with connectivity different from those in the 2D networks. Most of the higher dimensional complexes exhibit reversible, temperature-dependent spin-state conversion of high-temperature paramagnetic states to lower magnetic moment states having antiferromagnetic exchange within Cu–ON bonds upon cooling, with accompanying bond contraction. The 3D complex also exhibited antiferromagnetic exchange between CuII ions linked in chains through pyrimidine rings.