Crystal Structures And Fluorescent Properties Of Metal-bisphosphonate Coordination Polymers

Using the methods of second-ligand introduction and direct reaction underhydrothermal or solvothermal condition, we successfully synthesized twelvemetal-bisphosphonate coordination polymers (CPs) based on the(1-hydroxyl-2-(3-pyridyl)ethylidene-1,1-diphosphonic acid,(N-C5H4)CH2C(OH)(PO3H2)2, H5L1) and1-hydroxyl-yethylidenediphosphonate,(H2O3PC(OH)CH3PO3H2, H5L2). All compounds were structurally characterized by single-crystalX-ray diffraction together with powder X-ray diffraction and infrared spectroscopy. Inaddition, some of these compounds have also been studied by TG-DSC, cyclicvoltammogram (CV) and UV-vis spectrum. The chemical constitution formulas arelisted as follow:(1)[Cd(C5H4-NH)CH2C(OH)(PO3)(PO3H)](2)[Cu2(C5H4-N)CH2C(OH)(PO3)(PO3H)·H2O](3)[Cu1.5(C5H4-NH)CH2C(OH)(PO3H2)(PO3H)(C5H4-NH)CH2C(OH)(PO3)(PO3H)]·Cl(4){Zn1.5[(C5H4-NH)CH2C(OH)(PO3)2·2H2O]·3H2O}2(5)[Cu(C5H4-NH)CH2C(OH)(PO3)(PO3H)](6){Zn[(C5H4-NH)CH2C(OH)(PO3-H)2]2·4H2O}(7){Co3(4,4′-bipy)[CH2C(OH)(PO3)2(C5H4-N)CH2C(OH)(PO3)2]}·2H2O(8){Zn6[(2,2′-bipy)]4[(C5H4-NH)CH2C(OH)(PO3)2]4}·H2O(9)[Ba2((C5H4-NH)CH2C(O)(PO3)2)(WO3H)(H2O)2]Cl(10){Ni(2,2′-bipy)[CH3C(OH)(PO3H2)(PO3H)]}·H2O(11){Cu[CH3C(OH)(PO3H)(PO3H)](2,2′-bipy)}(12)0.5(H3NCH2CH2NH3)·{Co6[CH3C(OH)(PO3H)(PO3H)2][CH3C(O)(PO3H)(PO3H)][CH3C(OH)(PO3)2](2,2′-bipy)6Cl2}Among these metal-bisphosphonate CPs based on H5L1, compounds1~6wereobtained by the direct reaction method. Single-crystal X-ray diffraction indicates thatcompounds1,3,5have the similar structure. The polyhedron [MOn] is connected byone or more O–P–O bridges forming a1D inorganic chain. In2, the above1Dinorganic chain was further connected by an organic biphenyl moiety of H5L linkagesto form a2-D layer structure. Compound4has a novel2-D hybrid organic-inorganiclayer structure constructed from the polyhedron [ZnOn]. Compound6exhibits a3-D supramolecular network built from mononuclear zinc through hydrogen bonds. Byintroducing the second ligand2,2′-bipy/4,4′-bipy, respectively, we obtainedcompounds7and8. The single-crystal X-ray diffraction indicates that compound7has a3D structure, in which4,4′-bipy was not involved into the coordination but waslocated in the2-D channel. Compound8exhibits a3-D supramolecular network builtfrom1-D inorganic chain through hydrogen bonds. At the same time, compound9shows a2-D bimetallic structure built from inorganic chain by introducing thesilicontungstic acid.We also obtained compounds10~12by introducing a second organic ligand astemplate. Compound10has a3-D supramolecular structure constructed from theasymmetric nickel units. Compound11has a one-dimensional chain structureconstructed from mononuclear [CuO3N2] unit via edge-shared bridge O–P–O.Compound11possesses a3-D supramolecular structure built from hexanuclear Co(II)units through hydrogen bonds and π-π interactions.The TG-DSC investigations show that structures of compounds1,2,3,9,11,12are highly stable. For example, the skeleton collapse temperatures are450oC for2and500oC for9, respectively. The fluorescent measurements reveal that compounds1,2,3,4,5,9display two fluorescent emissions at about378nm and425nm based on thesame disphosphonate ligand. Compound11displays two fluorescent emissionscentered at382.5nm and424.5nm, while those of12are at374nm and424nm.Electrochemical studies of1,2and11reveal a higher electron donated ability.UV-vis spectra and the electron transfer mechanism for11are also investigated anddiscussed.