SYNTHESES, Structures and Fluorescent Properties of Two Zn(II)-Diphosphonate Coordination Polymers

With the introduction of 2,2 '-bipyridine (2,2 '-bipy) agent, two new zinc coordination polymers (CPs), {[Zn-6(HL-H)(4)(2,2 '-bipy)(4)]center dot 1/4H(2)O}(n)1and {[Zn-3(HL-H)(2)(H2O)(4)]center dot 6H(2)O}(n)2, have been hydrothermally obtained derived from diphosphonic acid, 1-hydroxy-2-(3-pyridyl)ethylidene-1,1-diphosphonic acid (H5L = (H4C5N)CH2C(OH)(PO3H2)(2), HL-H = (H4C5N-H)CH2C(OH)(PO3)(2)), and determined by single-crystal X-ray diffractions, elemental analysis, IR, powder X-ray diffractions (PXRD). The single-crystal X-ray diffractions reveal that compound1owns a novel 1-D fishbone-like inorganic chain structure built from binuclear building blocks [Zn-2(O-P-O)(2)](n)via [ZnO4](n)tetrahedron linkers. It is the first example thatN-heterlcyclic amine 2,2 '-bipy is used as the second ligand to construct the compound1with the diphosphonic acid ligand H5L. Both hydrogen bonding and pi-pi stacking interactions further extend the 1-D chain to the 3-D supramolecular network. Compound2exhibits a 2-D reticulate layer structure containing 4-, 8- and 16-membered rings created from 1-D ladder-like inorganic chain, and the organic pyridine rings in the structure point to voids defined by the 16-membered rings. Moreover, the room-temperature fluorescence measurements show that both the compounds display two fluorescent emissions centered at 379, 424 nm for1and 380, 424 nm for2, respectively, caused by intraligand pi*-pi emission state of organic pyridine ring (lambda(ex) = 235 nm). [GRAPHICS] .

Automated summary

Two new zinc coordination polymers were synthesized through hydrothermal method, with one possessing a novel 1-D fishbone-like structure and the other showing a 2-D reticulate layer structure. The organic pyridine rings in the compounds emit fluorescence, contributing to the extension of the compound's structure.