Cobalt and copper phosphinates based on N-(phosphinomethyl)iminodiacetic acid: supramolecular layered structures and magnetic properties

Abstract

Reactions of N-(phosphinomethyl)iminodiacetic acid (H₃L) and cobalt or copper salts in aqueous solutions result in two new metal phosphinates, [Co(H₂O)₆][Co₂L₂]·2H₂O (1) and [Cu(H₂O)₄][Cu₂L₂] (2). Both compounds exhibit different supramolecular layered structures, which result from the assembly of cationic and anionic moieties through hydrogen bond interactions. In 1, {Co₂O₂} dimers are linked through O–P–O units into a {[Co₂L₂]}_n²ⁿ⁻ double chain and [Co(H₂O)₆]²⁺ serve as a counterion. Compound 2 contains two kinds of chain-like moieties, i.e. {[Cu₂L₂]}_n²ⁿ⁻ and {[Cu(H₂O)₄]}_n²ⁿ⁺. The former is made up of corner-sharing {CuO₄N} square pyramids and {PHO₂C} tetrahedra and the latter is formed through edge-sharing connections of {CuO₆} octahedra. Magnetic studies reveal a dominant ferromagnetic interaction mediated between the magnetic centers in 1, while antiferromagnetic interactions are dominant in 2.