IntroductionThe efficacy of employing hydrogen bonding in the development of supramolecular architecturesviacrystal engineering is well established.1Robust organic and inorganic networks, or composites of them, may be readily generated by taking advantage of these hydrogen bond donor (D) and acceptor (A) interactions. The nature of the association is primarily driven by an electrostatic interaction and thus the charge distribution on the D/A system dictates the strength of the connection. Multiple D/A interactions similarly enhance the stability of the resultant framework. We are currently employing a combination of supramolecular and coordination chemistry in the development of topical architectures and novel networks.2In this way we aim to incorporate into the superstructures both the versatility, strength and directionality, and hence predictability, of hydrogen bonding with the chemical andphysical properties of transition metals.In our current studies we have been drawn to the polyprotic inorganic oxy-acids of some Group 15 elements (H2PO4−, PO43−, P2O74−, H2AsO4−, AsO43−,etc.) as they are potentially powerful hydrogen bond D/A moieties. These moieties are prevalent throughout nature and have been extensively studied in solid-state and materials chemistry and more recently in the hydrothermal synthesis of porous materials.3Apart from a few notable exceptions4they have been somewhat neglected in the development of metallo-supramolecular coordination chemistry. It has been recognised that some of these species, in their various deprotonated states in combination with simple cations, have been shown to form extended network structures in which hydrogen bondingis the main ordering mechanism.5This has given rise to crystalline solids possessing such phenomena as non-linear optical and ferroelectric properties. Furthermore, it has been proposed that tetrahedrally disposed oxo-anions of this group should propagate ferromagnetic coupling between copper(ii) centres bridged by them.6Following on from our recent success of employing phosphate and pyrophosphate to assemble Cu(ii) and Zn(ii) ions into extended networks,7we also desired a ligand that would itself promote intermolecular association. We therefore chose 2,2′-bipyridine, as it has been shown to engage in π–π interactions throughout ensuing crystal lattices and within the metal complexes it forms.8We describe here our latest results with this strategy and present the synthesis, structural characterisation and magnetic behaviour of {[(bipy)Cu(μ-H2AsO4)(H2AsO4)]2}n,1, which features a three dimensional supramolecular network, supported by a combination of coordination covalent, hydrogen bonding and face-to-face π–πinteractions.