Peijun Gong

Syntheses, structural characterization and photophysical properties of two series of rare-earth-isonicotinic-acid containing Waugh-type manganomolybdates

Two classes of rare-earth-organic-containing Waugh-type manganomolybdates (NH4)8{[RE(Hina)(ina)(H2O)2][MnIVMo9O32]}2·12H2O [RE = La3+ (1), Pr3+ (2), Nd3+ (3)] and (NH4)3[RE(Hina)2(H2O)6][MnIVMo9O32]·7H2O [RE = Sm3+ (4), Eu3+ (5), Gd3+ (6), Tb3+ (7), Dy3+ (8), Ho3+ (9), Er3+ (10), Tm3+ (11), Yb3+ (12), Y3+ (13)] (Hina = isonicotinic acid) were prepared by means of a step-by-step synthetic strategy and further characterized by IR spectroscopy, elemental analyses, UV-visible spectroscopy and single-crystal X-ray diffraction. X-ray diffraction indicates that 1–3 consist of an organic–inorganic hybrid dimeric {[RE(Hina)(ina)(H2O)2][MnIVMo9O32]}28− core constituted by two [MnMo9O32]6− units linked via a dinuclear {[RE(Hina)(ina)(H2O)2]2}4+ cation whereas 4–13 are composed of an organic–inorganic hybrid [RE(Hina)2(H2O)6]3+ fragment and one [MnMo9O32]6− polyoxoanion. It should be pointed out that the nature of RE cations controls these two structure types. As far as we know, 1–13 represent the first examples of Waugh-type manganomolybdates including rare-earth-organic subunits so far. Furthermore, their photocatalytic activities for the degradation of azophloxine were probed in aqueous medium and 3 and 8 as representatives were systematically investigated involving the influence of the optimal pH, catalyst dosage and the doping amount of VK-TA18 nanometer titanium dioxide on the photocatalytic activities. The solid-state photoluminescence properties and lifetime decay behaviors of 3, 4 and 5 in UV-visible or near-infrared regions were also examined at ambient temperature.

Ligand-Controlled Assembly of Heteropolyoxomolybdates Constructed from Plenary Keggin Germanomolybdates and Cu-Ln Heterometallic Units

By virtue of combining an in-situ assembly process with a stepwise synthesis in conventional aqueous solution, two series of unique organic-inorganic hybrid heteropolyoxomolybdates were constructed from plenary Keggin germanomolybdates and Cu-Ln heterometallic units and fully characterized: [H2 INA]2 H8 [LnCu(INA)4 (H2 O)6 ]2 [α-GeMo12 O40 ]3 ⋅52 H2 O (Ln=La3+ (1), Ce3+ (2), Pr3+ (3), Nd3+ (4), Sm3+ (5), Eu3+ (6); HINA=isonicotinic acid) and (NH4 )[Cu(PA)2 ][Cu(PA)2 Ln(H2 O)8 ][α-GeMo12 O40 ]⋅10 H2 O (Ln=Nd3+ (7), Sm3+ (8), Eu3+ (9); HPA=picolinic acid). The most remarkable structural characteristic of compounds 1-6 was that their molecular units were defined by three discrete plenary Keggin [α-GeMo12 O40 ]4- polyoxoanions and two organic-inorganic hybrid heterometallic [LnCu(INA)4 (H2 O)6 ]+ moieties, whereas compounds 7-9 exhibited a nice-looking 1D chain-like structure that was built from plenary [α-GeMo12 O40 ]4- polyoxoanions, pendent [Cu(PA)2 ] complexes, and bridging {[Cu(PA)2 ][Ln(H2 O)8 ]}3+ heterometallic groups. Notably, two different pyridine carboxylic acid ligands led to the discrepancy between the two structure types. To the best of our knowledge, compounds 1-9 constitute the first examples of plenary Keggin heterometallic germanomolybdates that include Cu-Ln-organic subunits. Further studies revealed that compounds 3 and 8 exhibited fast adsorption capacity for cationic dyes methylene blue (MB) and rhodamine B (RhB) in water. Moreover, compounds 3 and 8 could quickly and selectively adsorb MB from a mixture of MB/methyl orange (MO) or MB/azophloxine (Apo).