Layered copper compounds based on 4-(3-bromothienyl)phosphonate (BTP): weak ferromagnetism observed in [Cu2(4,4′-bpy)0.5(BTP)2]·H2O

Abstract

Two copper phosphonates based on 4-(3-bromothienyl)phosphonic acid (BTPH₂) with formula Cu(H₂O)(BTP) (1) and [Cu₂(4,4′-bpy)_0.5(BTP)₂]·H₂O (2) are reported. Compound 1 has a layered structure in which dimers of {Cu₂O₂}, made up of edge-sharing {CuO₆} octahedra, are bridged by both the {PO₃C} tetrahedra through corner-sharing and the water molecules. Compound 2 exhibits a novel layered structure where the {Cu₂(BTP)₂} columns, containing {Cu₄O₆} tetrameric cores and O–P–O linkages, are connected by 4,4′-bipyridine. In both cases, the 3-bromothienyl groups are grafted on the two sides of the layers. Magnetic studies reveal that antiferromagnetic interactions are mediated between the Cu(II) centers in 1, while for 2, weak ferromagnetism resulted from spin canting is observed. Electrochemical properties of compounds 1–2 are also investigated.