Insights on the binding ability of a new adenine analog: 7-amine-1,2,4-triazolo[1,5-a]pyrimidine. Synthesis and magnetic study of the first copper(ii) complexes

Abstract

Conventional reactions of the new multidentate ligand 7-amine-1,2,4-triazolo[1,5-a]pyrimidine (7atp, 1) with copper(II) salts lead to four novel multidimensional coordination complexes [Cu(7atp)(mal)(H₂O)₂]·H₂O (2), [Cu₂(μ-7atp)₄(H₂O)₂](ClO₄)₄·3H₂O (3), {[Cu(7atp)₂(μ-ox)]·3H₂O}_n (4) and {[Cu(7atp)₂(μ-suc)]·2H₂O}_n (5), where ox²⁻, mal²⁻ and suc²⁻ mean oxalate, malonate and succinate, respectively. In these compounds, the 7atp ligand coordinates monodentately through its atom N3, except for compound 3, which displays N3–N4 coordination mode, giving rise to all to structures with diverse topologies and dimensionality. Compound 2 is a mononuclear entity, 3 consists of dinuclear species, 4 is a zig-zag chain with oxalate as a bridging ligand and 5 is a succinate-bridged mono-dimensional system. All polynuclear metal complexes show antiferromagnetic interactions of with J values ranging from −0.12 to −49.5 cm⁻¹. The ligand donor capabilities have been estimated by topological analyses of the electron density (QTAIM) and electron localization function (ELF), obtained by DFT calculations. The compounds are the first structurally characterized copper(II) complexes containing the 7atp ligand.