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Piezoelectricity, one of the most desirable properties of non-centrosymmetric crystalline materials, has long been blooming in academic research, industrial manufacturing, and daily applications owing to its unique electromechanical transformation capability. Compared with inorganic piezoelectric ceramics dominating the market, molecule-based piezoelectric materials exhibit advantages of light weight, mechanical flexibility, and environment friendliness and have attracted widespread interest recently. However, investigations on molecular materials with large piezoelectric coefficients are mainly focused on organic–inorganic hybrids, while pure organic homochiral piezoelectrics holding large piezoelectric coefficients remain scarce. Herein, by precise molecular modification on (S)-2-methylpiperazin-1-ium perchlorate ([(S)-MPP][ClO4]) with polar cyanomethyl groups, a homochiral pure organic compound (3S)-3-methyl-1,4-di(cyanomethyl)piperazin-1-ium perchlorate [DCM-(S)-MPP][ClO4] with large d22 of 18 pC/N was achieved, along with changes in the space group from nonpolar to polar, giving rise to second harmonic generation and phase transition behaviors. The modification strategy proposed here will benefit piezoelectricity enhancement in more chiral compounds, promoting their application potential in biological medicine, flexible devices, and green chemistry. [ABSTRACT FROM AUTHOR]

By utilizing the pre-designed bi-functional ligand 4-{bis(4-benzoic)amino}-4H-1,2,4-triazole (H2L), five new transition-metal-based coordination polymers, namely, {[Zn(L)]·H2O·DMA}n (1), {[Zn2(L)2]·DMF}n (2),{[Mn(L)]·DMF}n (3), {[Cd(L)]·DMA}n (4) and [Cu3(OH)2(L)2]n (5) have been constructed and structurally characterized. In 1, the tetrahedral zinc ion was incorporated in the final structure. However, complexes 2, 3 and 4 bear 1D Zn-, Mn- and Cd-chains composed of metal ions, triazole and carboxyl groups, respectively. Differently, 1D [Cu4(μ3-OH)2] chains had been stabilized in the 3D structure of 5. In addition, the luminescence or magnetic properties of 1–5 had been correspondingly investigated with the consideration of their crystal structure. The whole research results manifest that utilizing a bi-functional ligand containing carboxyl and triazole groups is an efficient building method in constructing functional CPs. [ABSTRACT FROM AUTHOR]

Solvothermal reactions of two ligands with different geometries, derived from cyclotriphosphazene, hexakis(4-carboxylato-phenoxy)cyclotriphosphazene (H6L1) and hexakis(3-carboxylato-phenoxy)cyclotriphosphazene (H6L2) with Eu(NO3)3·6H2O in H2O/DMF under similar synthesis conditions produced three new compounds, namely, {[Eu2(L1)(H2O)4]·(H2O)4·(DMA)2}n (1), {[Eu2(L1)(H2O)8]·(H2O)2·DMA}n (2), and {[Eu2(L2)(H2O)3(DMF)]·(H2O)2·(DMA)}n (3). Compounds 1 and 2 display a 2D layer crystal structure with a distinct topological network incorporating the extended hexa-carboxylate ligand L1; in contrast, 3 has a 1D crystal structure with the highly distorted hexa-carboxylate ligand L2. In these three compounds, the ligands L1 and L2 are fully deprotonated, whose six extended carboxyl arms connect six different/same metallic nodes to generate metal–organic frameworks. The luminescence properties of three compounds have been studied at room temperature in relative detail. [ABSTRACT FROM AUTHOR]

Three three-dimensional (3D) supramolecular lanthanide complexes, {[Ln2(tdc)3(H2O)](H2O)2}n (Ln = La 1, Ce 2, Pr 3; H2tdc = 3,4-thiophenedicarboxylic acid), have been synthesized by hydrothermal reactions of H2tdc and the corresponding lanthanide nitrate. Crystallographic data show that 1–3 are isomorphous and crystallize in the triclinic P1̅ space group. Each of them exhibits an interesting pillared layered supramolecular network comprising polymeric layers and up-up-down-down (uudd) cyclic tetrameric water pillars. Furthermore, in these compounds, tdc2− anions unprecedentedly display three coordination modes in the polymeric layers. Elemental analyses (EA), infrared (IR) spectroscopy, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA) were also employed, and the materials exhibit a reversible de- and rehydration behavior. [ABSTRACT FROM AUTHOR]