Structural Effect of N‐7 Alkylation in 6‐Chloropurine on Cu (II) Binding: Effect of Anions and Magnetic Studies

Abstract

This study investigates the anion‐directed assembly of discrete copper (II) complexes. The ligands of choice are two unusual N7‐alkyl‐purine‐based neutral ligands. These ligands facilitate the exclusive coordination through the N3 and N9 positions, preventing polymeric chain formation. Perchlorate ions promoted the formation of discrete paddlewheel‐like complexes with the general formula [Cu2(μ‐Pur)4(CH3CN)2]4+, while chloride ions yielded chloride‐bridged dimers of the form [Cu2(Pur)2(μ‐Cl)2Cl2]. Copper‐copper bond distances within these complexes ranged from 2.92 to 2.98 Å. Magnetic susceptibility measurement of chloride‐bridged complexes exhibited antiferromagnetic coupling, whereas paddlewheel complexes displayed more complex alternating ferromagnetic and antiferromagnetic interactions. Chloride‐bridged compounds exhibited strong near‐infrared absorption.