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. © 2013 The Royal Society of Chemistry.