Synthesis and crystal structure of a new zinc diphosphonate

A new zinc diphosphonate [NH3CH(CH3)CH2NH3](2)Zn-2(edbbp)(2)(HNO3)(2)center dot 4H(2)O [eddbp = O3PCH(Ph)NH(CH2)(2)NHCH(Ph)PO3] was hydrothermally synthesized with Zn(NO3)(2)center dot 6H(2)O, ethane-1,2-diamino-N,N'-bis(benzylphosphonic acid) (H(4)edbbp) and 1,2-propyldiamine. It consists of a centro-symmetric dimeric unit [Zn-2(edbbp)(2)], in which each zinc ion adopts a distorted square-pyramidal coordination geometry. Hydrogen bonds formed between phosphonate groups and protonated 1,2-propyldiamine molecules link the dimeric units into one-dimensional chains. The doubly protonated 1,2-propyldiamine molecules serve not only as charge compensating counter ions, but also as bridging groups. Hydrogen-bonding interactions among the phosphonate oxygen atoms, water molecules, nitric acid molecules and protonated 1,2-propyldiamine result in the formation of a three-dimensional supramolecular network.