Abstract
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 = H2O3PCH2N(C4H8)NCH2PO3H2),N,N′-piperazinebis(methylenephosphonic acid), (L-H2= O3PH2CHN(C4H8)NHCH2PO3) have been hydrothermally synthesized and characterized by elemental analysis, FT-IR, PXRD, TG-DSC, and single-crystal X-ray diffraction. Compound1possesses a 2D inorganic-organic alternate arrangement layer structure built from 1D inorganic chains through the piperazine bridge, in which the ligand L−4shows two types of coordination modes reported rarely at the same time. In1, both crystallographic distinct Ba(1) and Ba(2) ions adopt 8-coordination two caps and 9-coordination three caps triangular prism geometry structures, respectively. Compound2possesses a zero-dimensional mononuclear structure with two crystallographic distinct Mg(II) ions. Free metal cations [MgO6]n2+and uncoordinated anions(L-H2)n2-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 for1and 302 nm, 378 nm, and 434.5 nm for2(λex=235 nm), respectively. The high energy emissions could be derived from the intraligandπ∗-ntransition stations ofH4L(310 nm and 382 nm,λex=235 nm), while the low energy emission (>400 nm) of1-2may be due to the coordination effect with metal(II) ions.
Highlights
O3PH2CHN(C4H8)NHCH2PO3) have been hydrothermally synthesized and characterized by elemental analysis, FT-IR, powder X-ray diffraction (PXRD), TG-DSC, and single-crystal X-ray diffraction
Most of its associated works have focused on the assembly of the transition metals, dd10-block metals, and lanthanides metal-organic open frameworks [5,6,7,8,9,10,11,12,13,14]. e other important task is the choice of metal ion in the formation of coordination polymers (CPs)
Some shortcomings of itself, such as the tendency of forming solvated species and their unpredictable coordination numbers, are keeping them weighted down. erefore, our research has focused on the synthesis and photoluminescence of phosphonate CPs based on alkaline-earth metals
Summary
E design and synthesis of coordination polymers (CPs) based on phosphonates have always been the most important part of the work for the researchers. is is due to their complicated structural diversity and their potential applications in optics, catalysis, magnetism, molecular sensing and separation, gas adsorption, and molecular recognition [1,2,3,4]. e choice of functionalized organic skeleton is the rst important task in the construction of phosphonate CPs. e ligand H4L, as a type of multidentate ligand (O- and/or N-donor), can be protonated and/or deprotonated to produce H3L−, H2L2−, HL3−, and L4− with versatile metal-binding and hydrogen-bonding capabilities. E design and synthesis of coordination polymers (CPs) based on phosphonates have always been the most important part of the work for the researchers. E other important task is the choice of metal ion in the formation of CPs. Alkaline-earth metals are reasonably good candidates due to their variable stereochemical activity, exible coordination environment, cheaper prices, and low toxicity. A series of alkaline-earth coordination compounds with novel structures and properties have been reported [15,16,17,18]. Erefore, our research has focused on the synthesis and photoluminescence of phosphonate CPs based on alkaline-earth metals. We hope to get further information on structures and properties of the alkaline-earth phosphonate CPs. We discuss the structures of the two alkaline-earth M(II) phosphonate CPs, namely, [Ba2(L)(H2O)9]⋅3H2O (1) and [Mg1.5(H2O)9]⋅(L-H2)1.5⋅6H2O (2), along with their uorescent properties
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