Structures and spectroscopy studies of two M(II)-phosphonate coordination polymers based on alkaline earth metals (M = Ba,Mg)

The two examples of alkaline-earth m(ii)-phosphonate coordination polymers,[ba2(l)(h2o)9]·3h2o (1) and [mg1.5(h2o)9]·(l-h2) 1.5·6h2o (2) (h4l = h2o 3pch2n(c4h8)nch2po 3h2),n,n′-piperazinebis(methylenephosphonic acid),(l-h2 = o3ph2chn(c4h 8)nhch2po3) have been hydrothermally synthesized and characterized by elemental analysis,ft-ir,pxrd,tg-dsc,and single-crystal x-ray diffraction. compound 1 possesses a 2d inorganic-organic alternate arrangement layer structure built from 1d inorganic chains through the piperazine bridge,in which the ligand l-4 shows two types of coordination modes reported rarely at the same time. in 1,both crystallographic distinct ba(1) and ba(2) ions adopt 8-coordination two caps and 9-coordination three caps triangular prism geometry structures,respectively. compound 2 possesses a zero-dimensional mononuclear structure with two crystallographic distinct mg(ii) ions. free metal cations [ mgo 6 ] n 2 + and uncoordinated anions (l - h 2) n 2 - are joined together by static electric force. results of photoluminescent measurement indicate three main emission bands centered at 300 nm,378.5 nm,and 433 nm for 1 and 302 nm,378 nm,and 434.5 nm for 2 ( ex = 235 nm),respectively. the high energy emissions could be derived from the intraligand π * - n transition stations of h 4 l (310 nm and 382 nm,ex = 235 nm),while the low energy emission (>400 nm) of 1-2 may be due to the coordination effect with metal(ii) ions. © 2013 kui-rong ma et al.