Two series of novel organic–inorganic hybrid carboxylated rare-earth-substituted monolacunary Dawson-type phosphotungstate monomers [Hdap] ­[RE­(H2O)­(Hpic)3]­[RE­(Hpic)2 (α2-P2W17O61)]­·21H2O [RE = GdIII (1), TbIII (2), DyIII (3), HoIII (4), ErIII (5), TmIII (6), YbIII (7), YIII (8); Hpic = 2-picolinic acid, dap = 1,2-diaminopropane] and dimers [H2dap]8­[RE2(H2ox)2­(ox)­(α2-P2W17O61)2]­·25H2O [RE = HoIII (9), ErIII (10), TmIII (11), YbIII (12), YIII (13); H2ox = oxalic acid] have been hydrothermally synthesized and characterized by elemental analyses, IR spectra, thermogravimetric measurements, and X-ray single-crystal diffraction. The monomeric polyoxoanion skeleton of isomorphic 1–8 is constructed from a monolacunary Dawson-type phosphotungstate implanted by a [RE1­(Hpic)2]3+ cation in the polar position and supported by the other [RE2(H2O)­(Hpic)3]3+ cation on the equatorial belt. Interestingly, two kinds of RE cations separately coordinate to two or three Hpic ligands in the form of N–C–C–O–RE containing five-membered ring fashion. The dimeric polyoxoanion backbone of isomorphic 9–13 is built by two mono-RE substituted Dawson-type phosphotungstate fragments [RE­(H2ox)­(α2-P2W17O61)]7– joined together by an ox2– linker. The visible photoluminescence spectra of solid-state 2, 3, 5, and 10 and the NIR photoluminescence properties for solid-state 5, 10, 7, and 12 at ambient temperature have been carried out, which are mainly derived from the RE3+ f–f electron transitions. Magnetic susceptibility measurements and fitting results of 3 demonstrate that 3 is a single-molecule magnet.

Cyclic voltammetry, 1H nuclear magnetic resonance and quantum chemistry calculations were applied to explore the hydrogen bond interactions between ascorbic acid (AA) and glycine. The experimental results demonstrate the existence of hydrogen bonds in AA-glycine system, which has a significant effect on the oxidation peak potentials and currents of AA and the chemical shifts of glycine. The formation of hydrogen bonds between AA and glycine were further confirmed by the density functional theory, quantum theory of atoms in molecules and natural bond orbital analyses.

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