Counter-anions and their coordination behavior with Cu(II) complexes of thiophen-3-yl-dipicolylamine

A new ligand, 1-(pyridin-2-yl)-N-(pyridin-2-ylmethyl)-N-(thiophen-3-ylmethyl)methanamine, ThDPA, was synthesized, as a new example of an N3S donor. Cu(II) complexes of this ligand were isolated. When Cu(NO3)2 was used as the metal source, a homobinuclear complex with the formula [CuThDPA(NO3)2]2·H2O, 1, with two different types of nitro coordination was isolated. 1 crystallizes in the monoclinic P21/n space group with a = 15.193, b = 8.181, c = 32.827 Å, β = 103.3° and V = 3971.9 Å3. In the case of CuSO4 as the source of copper(II), uncommon sulfato-bridged structures were isolated. The homobinuclear complex crystallized in two different lattices, depending on the solvent evaporation rate. Compound 2, with the formula [CuThDPA(SO4)]2·3H2O, crystallizes with 3 water molecules per binuclear structure in the monoclinic space group P21/c with a = 10.143, b = 17.013, c = 11.793 Å, β = 97.18° and V = 2019.1 Å3, and 3, [CuThDPA(SO4)]2·4H2O, crystallizes with 4 water molecules per binuclear structure in the triclinic P1¯ space group, with a = 9.2906, b = 10.7297, c = 12.7236 Å, α = 79.66, β = 72.18, γ = 67.1° and V = 1109.7 Å3.

A new N3S chelating ligand bearing thiophene and dipicolylamine has been synthesized and its Cu(II) complexes isolated. The structure of the complexes depends strongly on the coordinated counter-anion, NO3- or SO42-. SO42- serves a bridging anion yielding an uncommon homobinuclear complex, while NO3- coordinated either bidentate or monodentate in a mononuclear complex.Figure optionsDownload as PowerPoint slide