Supramolecular assembly of substituted hydroxy-bisphosphonates with cupric ion. Influence of the chain functionalization

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Abstract
As part of a general study of hydroxy-bisphosphonic acids (HEBP), R-C(OH)(PO3H)2, three Cu (II) complexes with R˭CH3; R˭-(CH2)3-NH2 and R˭-(CH2)5-NH2, were prepared and analysed by X-Ray diffraction methods. The substitution of the methyl group in HEBP (3) by an aminopropyl (1) or by an aminopentyl (2) chain led to a drastic modification of the ionic self-assembly in the crystal and completely different polyhedral complexation networks around the Cu (II). A polymeric chain formation is observed in (3), whereas (1) and (2) display discrete tetrameric and dimeric arrangements. The results are discussed on the basis of the environment of the phosphorus atoms and the molecular geometry around the central carbon atom of the hydroxy-bisphosphonic moiety. These results are further compared to their ability for ionic transport and/or extraction.