Novel manganese(ii) and cobalt(ii) 2D polymers containing alternating chains with mixed azide and carboxylate bridges: crystal structure and magnetic properties

Abstract

Two coordination polymers formulated as [Mn₃(L¹) (N₃)₆(H₂O)₄] (1) and [Co₃(L²) (N₃)₆(H₂O)₅] (2) (L¹ = 1,1′-bis(4-carboxylatobenzyl)-4,4′-bipyridinium, L² = 1,2,4,5-tetrakis(4-carboxylatopyridinium-1-methylene)benzene) were synthesized and structurally and magnetically characterized. Both compounds 1 and 2 contain alternating chains constructed by azide and carboxylate bridges. The independent sets of bridges alternate in an A1A1BA1A1 sequence between adjacent Mn(II) ions in 1: [(EO-N₃)(OCO)] double bridges (EO = end-on) (denoted as A1) and (EO-N₃)₂ double bridges (denoted as B) and the alternation mode is in an A2A2BA2A2 sequence between adjacent Co(II) ions in 2: [(EO-N₃)(OCO)₂] triple bridges (denoted as A2) and (EO-N₃)₂ double bridges (denoted as B). The alternating chains are interlinked into 2D coordination layers respectively by the L¹ and L² ligands. Magnetic studies demonstrate that the [(EO-N₃)(OCO)] and (EO-N₃)₂ double bridges mediate antiferromagnetic coupling between Mn(II) ions in 1 while the [(EO-N₃)(OCO)₂] triple and (EO-N₃)₂ double bridges mediate ferromagnetic coupling between Co(II) ions in 2.