Novel copper materials based on the self-assembly of organophosphonic acids and bidentate amines

Abstract

The hydrothermal synthesis and crystal structure of seven new supramolecular, heterocyclic adducts of copper organophosphonates are presented. Compounds 1–4, [CuX(D)₂][C₆H₅P(O)(OH)₂] [C₆H₅P(O)₂(OH)], where D = 1,10-phenanthroline (phen) and X = Cl (1), Br (2), I (3), and NCS (4), are ionic in nature and possess a monoclinic structure, with the copper(II)-halide bond lying along a two-fold crystallographic axis. The crystals exhibit an alternating, lamellar structure in which 1-D ‘ribbons’ of [CuX(phen)₂]⁺ cations are interleaved with 2-D ‘sheets’ of anionic [C₆H₅P(O)(OH)₂][C₆H₅P(O)₂(OH)]⁻ dimers. The ribbons are associated through π–π bonding of the heterocyclic rings, and the acid sheets through a combination of π–π bonding of the aromatic rings, and hydrogen-bonding between the PO and P–OH of neighbouring acid dimers. Analogous derivatives have also been prepared by the reaction of [Cu(phen)₂]Br with benzylphosphonic acid (5), [Cu(2,2′-bipy)₂]I with phenylphosphonic acid (6) and [Cu(phen)₂]I with phenylsulfonic acid (7). These complexes did not produce crystals suitable for single-crystal analysis. However, compounds (5) and (7) are thought to have similar structures to 1–4, whilst compound (6) has a different (2 : 2 : 3) ratio of copper : phosphonate : amine. Thus the supramolecular structure is robust for phenyl- and benzyl-phosphonic acids, with Cl, Br, I and NCS copper(II)phen complexes, and slightly varied by the presence of phenylsulfonic acid, but is not observed in the presence of 2,2′-bipy.