Benzotriazole based 1-D, 2-D and 3-D metal dicyanamide and tricyanomethanide coordination networks

The 1-methylbenzotriazole ligand (1-Mebta) has been successfully incorporated into four new 1-D coordination polymers of general formula [MII(dca)2(1-Mebta)2] (M = Mn (1), Fe (2) and Cu (3)) and [CuII(tcm)2(1-Mebta)2] (4) containing the dicyanamide (N(CN)2-,dca-) or tricyanamide (C(CN)3-,tcm-) μ1,5-bridging ligands. Magnetic susceptibility measurements reveal weak antiferromagnetic interactions between the MII centres without any long-range order. Spin-Hamiltonian parameters (g = ±0.01, J = ±0.01) were obtained using a chain model; [MII(dca)2(1-Mebta)2] (Mn (1): g = 1.94, J = −0.15 cm−1, Fe (2): g = 2.17, J = −0.38 cm−1, and g = 2.18, J = −0.01 cm−1) in [CuII(tcm)2(1-Mebta)2] (4). To increase the dimensionality of these benzotriazole-based networks, two benzotriazole molecules were linked together via alkyl chains in the form of the 1,3-di(benzotriazol-1-yl)propane (dbtp) and 1,4-di(benzotriazol-1-yl)butane (dbtb) ligands and these have produced 1-D, 2-D and 3-D networks. The dbtp ligand yields a 1-D ‘step-like’ chain coordination polymer in [CuII(dca)2(dbtp)](5), where the dbtp ligands propagate the 1-D chains; a role normally carried out by bridging dca− ions. Reaction of the dbtp ligand with CoII increases the dimensionality by producing the α-Po related 3-D [CoII(dca)2(dbtp)] (7) network. Compound 7 consists of 2-D (4,4) connecting sheets, linked together by the bridging dbtp ligand. The NiII analogue [NiII(dca)2(dbtp)] (8) has also been synthesized in polycrystalline form and characterized by powder X-ray diffraction. Magnetic measurements on 7 indicate extremely weak antiferromagnetic exchange interactions between the CoII ions while [NiII(dca)2(dbtp)] (8) exhibits short range ferromagnetic coupling with best-fit parameters g = 2.13 and J = +0.24 cm−1. The synthesis of a 2-D (4,4) connected sheet [CuII(dca)2(dbtb)] (9) (where dbtb is 1,4-di(benzotriazol-1-yl)butane) illustrates how increasing the alkyl chain by one carbon length has dramatically changed the topology and dimensionality of the network. Magnetic susceptibility measurements reveal weak antiferromagnetic exchange coupling.

The synthesis, structure and magnetism of benzotriazole based 1-D, 2-D and 3-D metal dicyanamide and tricyanomethanide coordination networks are described.Figure optionsDownload as PowerPoint slide