Jingwen Sun

Two unusual 3D POM-Ag frameworks with tetragonal and dodecagonal helical channels.

Two new hybrid compounds with tetragonal and dodecagonal helical channels, K[Ag14(pyttz)4(H2O)2][PW12O40]2⋅(OH)⋅5 H2O (1) and K[Ag14(pyttz)4(H2O)4][HSiW12O40]2⋅H2O (2), have been hydrothermally synthesized and structurally characterized by using routine techniques. X-ray diffraction analysis shows that compounds 1 and 2 are isostructural and crystallize in the monoclinic space group P2(1)/c. A fascinating structural feature of these compounds is that they form 3D POM-Ag frameworks with helical channels, which are the first examples of helical channels that are constructed from POMs and metal atoms. Notably, there are two types of spatial orientation of the POMs, which result in the formations of left- and right-handed helical chains. Furthermore, these different helical chains are perfectly enclosed through shared POMs, thereby forming tetragonal and dodecagonal helical channels. In addition, the photocatalytic degradation of RhB by these compounds was also investigated.

Assembly of the first polyoxometalate-based hybrid with [ring+helix] channels and photocatalytic activity

A new compound containing [helix+ring] double configuration channel constructed from 216-membered macrocycle and left- and right-handed helical chains was synthesized and structurally characterized: K2[Ag6(pytz)4][PW12O40] (pytz = 5-(pyridyl)tetrazolate). The smart pytz ligand plays an important role in the formation of the [helix+ring] double configuration channel, as shown by X-ray diffraction analysis. The new compound represents the first example of helical channels with [helix+ring] double configuration. The results of the photocatalytic degradation of RhB and the photocatalytic mechanism indicate that the [helix+ring] double configuration channel with lower enthalpy prohibits the conglomeration and deactivation of POMs, which allows for the enhancement of its catalytic properties.

Immobilization of Polyoxometalate in the Metal-Organic Framework rht-MOF-1: Towards a Highly Effective Heterogeneous Catalyst and Dye Scavenger

A series of three remarkable complexes [PMo12O40]@[Cu6O(TZI)3(H2O)9]4·OH·31H2O (H3TZI = 5-tetrazolylisophthalic acid; denoted as HLJU-1, HLJU = Heilongjiang University), [SiMo12O40]@[Cu6O(TZI)3(H2O)9]4·32H2O (denoted as HLJU-2), and [PW12O40]@[Cu6O(TZI)3(H2O)6]4·OH·31H2O (denoted as HLJU-3) have been isolated by using simple one-step solvothermal reaction of copper chloride, 5-tetrazolylisophthalic acid (H3TZI), and various Keggin-type polyoxometalates (POMs), respectively. Crystal analysis of HLJU 1−3 reveals that Keggin-type polyoxoanions have been fitted snuggly in the cages of rht-MOF-1 (MOF: metal−organic framework) with large cell volume in a range of 87968−88800 Å3 and large pore volume of about 68%. HLJU 1–3 exhibit unique catalytic selectivity and reactivity in the oxidation of alkylbenzene with environmental benign oxidant under mild condition in aqueous phase as well as the uptake capacity towards organic pollutants in aqueous solution.

Construction of POMOFs with different degrees of interpenetration and the same topology

Three metal–organic networks with different degrees of interpenetration based on Keggin-type polyoxometalates have been hydrothermally synthesized by a simple change in the organic ligand and structurally characterized. By changing the length and the coordination mode of the ligand, we obtained compound 1 which represents the first example of a three-fold interpenetrated POMOF architecture with pcu topology, and POMs occupy the vertex of the pcu lattice. Compound 2 exhibits a POM-pillared metal–organic framework, which can be described overall as a two-fold interpenetrated pcu framework, and POMs occupy the arris of the pcu lattice. Different from 1 and 2, compound 3 can be described as a single pcu network and POMs occupy the face of the pcu lattice. The influence of the organic ligand on the degree of interpenetration is also discussed. Furthermore, the results indicate that the three compounds present good photocatalytic activities.

2D l-Di-toluoyl-tartaric acid Lanthanide Coordination Polymers: Toward Single-component White-Light and NIR Luminescent Materials.

A series of five l-di-p-toluoyl-tartaric acid (l-DTTA) lanthanide coordination polymers, namely {[Ln4 K(4)  L6 (H2O)x ]⋅yH2 O}n , [Ln=Dy (1), x=24, y=12; Ln=Ho (2), x=23, y=12; Ln=Er (3), x=24, y=12; Ln=Yb (4), x=24, y=11; Ln=Lu (5), x=24, y=12] have been isolated by simple reactions of H2L (H2 L= L-DTTA) with LnCl3 ⋅6 H2O at ambient temperature. X-ray crystallographic analysis reveals that complexes 1-5 feature two-dimensional (2D) network structures in which the Ln(3+) ions are bridged by carboxylate groups of ligands in two unique coordinated modes. Luminescent spectra demonstrate that complex 1 realizes single-component white-light emission, while complexes 2-4 exhibit a characteristic near-infrared (NIR) luminescence in the solid state at room temperature.

The racemate-to-homochiral approach to crystal engineering via chiral symmetry breaking

The racemate-to-homochiral approach is a method to transform or separate a racemic mixture into homochiral compounds. This protocol, if without an external chiral source, is categorized into chiral symmetry breaking. The resolution processes without chiral induction are highly important for the investigation of the origin of homochirality in life, pharmaceutical synthesis, the chemical industry and materials science. Besides the studies on the models and mechanisms used to explain the racemate-to-homochiral approach which may give the probable origin of homochirality in life, recent developments in this field have been plotted towards the separation of enantiomers for the synthesis of pharmaceuticals and chiral chemicals. Direct synthesis of chiral metal–organic framework (MOF) coordination polymers has been achieved as well. In this highlight, we will disclose the comparison of spontaneous resolution and chiral symmetry breaking resolution, and describe the evolution of models and mechanisms for chiral symmetry breaking resolution and its applications in enantiomer resolution and materials science.

A series of lanthanide(III) complexes constructed from Schiff base and β-diketonate ligands

A series of lanthanide(III) complexes constructed from Schiff base and β-diketonate ligands have been synthesized by the same method. They are mononuclear complex [Ln(hfac)3(L)] (Ln = Nd (1), Sm (2), Eu (3)), tetranuclear complex [Gd4(OAc)2(hfac)10(L)3] (4), dinuclear–mononuclear cocrystal {[Dy(hfac)2(L)]2(OAc)}·[Dy(hfac)4] (5), and mononuclear–mononuclear cocrystal [Yb(hfac)2(L)]·[Yb(hfac)4] (6) (L = N,N′-bis(pyridine)-1,2-ethanediamine, hfac = hexafluoroacetylacetonate). Complexes 1–3 and 6 exhibit characteristic metal-centred emission not only in the solid state but also in solution. Lifetimes and quantum yields of luminescence are also determined.

In situ recrystallization of lanthanide coordination polymers: from 1D ladder chains to 1D linear chains

Reactions of LnCl3·6H2O (Ln = La, Ce, Pr, Nd, Gd and Lu), L-dibenzoyl tartaric acid (L-DBTA) and triethylamine in a methanol–water solution afford four complexes 1a–4a with 1D ladder chain structures, e.g. {[Ln2(L-DBTA)3(CH3OH)x(H2O)y]·zH2O}n (x = 3 or 4, y = 3 or 4, z = 2 or 5; Ln = La (1a), Ce (2a), Pr (3a) and Nd (4a)) and two complexes 5 and 6 with 1D linear chain structures, e.g. {Et3NH[Ln(L-DBTA)2(CH3OH)2(H2O)2]·2H2O}n (Ln = Gd (5) and Lu (6)). Accidentally, an in situ irreversible SCSC transformation from the kinetically stabilized 1D ladder chain structures of 1a–4a to thermodynamically stabilized 1D linear chain structures of 1–4 was observed, which was seldom reported for lanthanide coordination polymers. The coordination stability around a lanthanide cation was investigated to expatiate on the irreversible SCSC transformation. The solid-state NIR luminescence for complexes 3a, 3, 4a and 4 was also studied.