Ligand dependent self-assembly of hydroxido-bridged dicopper units templated by sodium ion

Abstract

Crown-ether like interaction of two neutral [Cu₂(μ-OH)(μ-L¹)] (H₃L¹ = 2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) fragments, around a central Na⁺ cation as self-assembly template, led to the formation of [Na{Cu₂(μ-OH)(μ-L¹)}₂]ClO₄ (1). Di-tert-butyl group substituted H₃L² {2-(3,5-di-tert-butyl-2-hydroxyphenyl)-1,3-bis[4-(3,5-di-tert-butyl-2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine} conversely yields only [Cu₂(μ-OH)(μ-L²)]·1.5H₂O (2), by discarding aggregation around the Na⁺ ion. The crown-ether type aggregate 1 exhibits ferromagnetic interactions within the double oxido-phenoxido [Cu₂] fragments and weak antiferromagnetic interactions are mediated by the O⋯Na⁺⋯O bridges. Complex 2 registers only weak antiferromagnetic interactions within the oxido-phenoxido bridged [Cu₂] entity. UV-visible and emission titration spectroscopy establish the interaction of cationic complex 1 with calf thymus DNA in Tris buffer and it cleaves supercoiled pBR322 DNA from in situ generated ROS.