Linggen Kong

Dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI) complexes with a tridentate Schiff base ligand

The complexation of a julolidine–quinoline based tridentate ligand with three oxo-metal ions, dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI), has been investigated with four new complexes being synthesised and structurally characterised. (VO2L)·2/3H2O (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} has a VO2L neutral mononuclear structure with a five-fold coordinated vanadium metal centre in a distorted trigonal bipyramidal geometry. (ReOL2)2(ReCl6)·7DMF (2) [DMF = dimethylformamide] exhibits a mixed valent rhenium complex with a (ReOL2)+ cationic unit in a distorted octahedral metal coordination geometry, charge balanced with (ReCl6)2− anions. [(UO2)L(H2O)2]2·2(NO3)·HL·4H2O (3) and [(UO2)L(CH3OH)2](NO3)·CH3OH (4) both have (UO2L)+ cationic mononuclear structures with either coordinated water or methanol molecules in pentagonal bipyramidal coordination geometries for the uranium metal centres. Intra-/intermolecular interactions including hydrogen bonding and π–π interactions are common and have been discussed. In addition, optical absorption and photoluminescence properties have been investigated.

Hydrothermal synthesis, structures and magnetic properties of two new holmium(III) oxalato complexes

Abstract Two new holmium (Ho) oxalato complexes have been synthesized under hydrothermal conditions and structurally characterized. [Ho(OH)2]2(C2O4) (1) has a 3-D structure with Ho-(μ3-OH) hydroxide layers connected by μ4-bridging oxalate ligands forming a unique hybrid structure. Sr(H2O)4[Ho(C2O4)2(H2O)]2·2H2O (2) has a 3-D structure built through μ2-bridging oxalate ligands connecting hexagonal Ho oxalate layers with hydrated Sr2+ ions in the channels. Different oxalate ligand arrangements around the metal ions control the structural alterations among the lanthanoid double oxalates even with similar formulas. Both structures have been discussed and compared to the existing lanthanoid oxalato complexes. In addition, their vibration modes, thermal stabilities, electronic structures, and magnetic properties have been further investigated and reported. Both 1 and 2 show the deviation of the magnetic behaviors from the Curie–Weiss law due to the crystal field effects.

Uranyl oxide hydrate phases with heavy lanthanide ions: [Ln(UO2)2O3(OH)]·0.5H2O (Ln = Tb, Dy, Ho and Yb)

Four uranyl oxide hydrate phases with heavy lanthanide ions, [Ln(UO2)2O3(OH)]·0.5H2O [Ln = Tb (1), Dy (2), Ho (3) and Yb (4)], have been synthesized under hydrothermal conditions at 240 °C and characterized. SEM-EDS revealed that these phases have very similar thin plate morphologies with a U to Ln atomic ratio of 2 : 1, which is further confirmed by TEM-EDS. Their high magnification TEM bright field images showed small crystalline domains (∼2–5 nm) with preferred crystal orientations. Both XRD and TEM SAED confirmed that they crystallize in the trigonal crystal system with the Pm1 space group. Raman characterization revealed the typical vibration modes for the uranyl units with the calculated UO bond lengths are comparable to the values reported for other UOH phases with d-transition metal ions as the interlayer species. The possible presence of a pentavalent uranyl unit has been ruled out by UV-vis-NIR spectroscopy. The thermal and optical properties have also been investigated and reported.