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

Abstract

The 1-methylbenzotriazole ligand (1-Mebta) has been successfully incorporated into four new 1-D coordination polymers of general formula [M II(dca) 2(1-Mebta) 2] (M = Mn ( 1), Fe ( 2) and Cu ( 3)) and [Cu II(tcm) 2(1-Mebta) 2] ( 4) containing the dicyanamide ( N ( CN ) 2 - , dca - ) or tricyanamide ( C ( CN ) 3 - , tcm - ) μ 1,5-bridging ligands. Magnetic susceptibility measurements reveal weak antiferromagnetic interactions between the M II centres without any long-range order. Spin-Hamiltonian parameters ( g = ±0.01, J = ±0.01) were obtained using a chain model; [M II(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 [Cu II(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 [Cu II(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 Co II increases the dimensionality by producing the α-Po related 3-D [Co II(dca) 2(dbtp)] ( 7) network. Compound 7 consists of 2-D (4,4) connecting sheets, linked together by the bridging dbtp ligand. The Ni II analogue [Ni II(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 Co II ions while [Ni II(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 [Cu II(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.