Single‐Strand Molecular Wheels and Coordination Polymers in Copper(II) Benzoate Chemistry by the Employment of α‐Benzoin Oxime and Azides: Synthesis, Structures, and Magnetic Characterization

Abstract

AbstractThe use of α‐benzoin oxime (bzoxH2) in copper(II) benzoate chemistry, in the absence or presence of ancillary azido ligands, is reported. The reaction of Cu(O2CPh)2·2H2O with one equivalent of bzoxH2 in N,N‐dimethylformamide (DMF) affords the decanuclear complex [Cu10(bzox)10(DMF)4] (1) in good yield. Dissolution of 1 in CH2Cl2 leads to the subsequent isolation of the solvent‐free complex [Cu10(bzox)10] (2) in moderate yields. Complexes 1 and 2 are isostructural and possess a loop or single‐strand molecular wheel topology. The bzox2– dianions behave as η1:η1:η2:μ3 ligands, which give rise to an overall [Cu10(μ‐ONR)10(μ‐OR′)10] core. Both 1 and 2 stack to form nanotubular columns with beautiful supramolecular architectures. The reaction of Cu(O2CPh)2·2H2O with bzoxH2 and NaN3 in a 1:1:1 molar ratio in MeOH gives the bzoxH2‐free complex [Cu(N3)(O2CPh)(MeOH)]n (3), which is a 1D chain. The CuII atoms in 3 are linked by a single, end‐on N3– group, a syn,syn‐η1:η1:μ PhCO2– ion, and an oxygen atom from the bridging MeOH ligand. The 1D chains are hydrogen bonded into 2D sheets through Nazide···H(OMeOH) interactions. Variable‐temperature, solid‐state direct‐current magnetic studies were carried out on 1–3. The data for 1 and 2 indicate very strong antiferromagnetic exchange interactions and a S = 0 ground state, which is expected for even‐membered loop arrays of CuII atoms. In contrast, 3 exhibits ferromagnetic exchange interactions; the data were fitted to the appropriate equation derived from the Hamiltonian H = –JΣ(Si·Si+1), which includes a zJ′ interchain interaction term. The best‐fit parameters were J = +49.6(4) cm–1, g = 2.067(3), and zJ′ = 2.3(1) K. The combined results demonstrate the ligating flexibility of both the bzoxH2 and azido groups and their usefulness in the synthesis of polynuclear CuII clusters and coordination polymers.