Wei-Hui Fang

Cubic Polyoxometalate−Organic Molecular Cage

Tris(hydroxymethyl)aminomethane (Tris) was successfully grafted onto the surface of a Ni(6)-substituted polyoxotungstate formed in situ to further generate a three-connected polyoxometalate building block. The cooperative assembly of Tris functionalized three-connected building blocks and rigid 1,3,5-benzenetricarboxylate gave rise to an unprecedented cubic polyoxometalate-organic molecular cage with high thermal and hydrothermal stability.

A Series of Open-Framework Aluminoborates Templated by Transition-Metal Complexes

A series of open-framework aluminoborates (ABOs) [M(dien)(2)][AlB(6)O(11)(OH)] (M=Co (I a), Ni (I b), Cd (I c), Zn (I d); dien=diethylenetriamine) and [M(en)(3)][AlB(7)O(12)(OH)(2)] (H(2)O)(0.25) (M=Co (II a), Ni (II b); en=ethylenediamine) have been made under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, UV/Vis and fluorescence spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction, and nonlinear optical determination. These compounds were classified as two structural types: Type I (I a-d) contains AlO(4) tetrahedra and B(6)O(11)(OH) clusters, which link to form a new 3D framework with 7-/9-ring helical channels and large 13-ring channels; whereas type II (II a,b) is composed of AlO(4) tetrahedra, chainlike B(4)O(6)(OH)(2) tetramer, and crablike B(6)O(12) clusters, which interconnect to form other new 3D frameworks with 8-ring helical channels, rare 16-ring double-helical channels, and larger odd 15-ring channels. These compounds represent the first examples of 3D ABOs templated by transition-metal complexes (TMCs). I c,d present good second harmonic generation (SHG) properties. UV/Vis spectral investigation indicates that I a-d and II a,b are wide-band-gap semiconductors.

A series of lanthanide-based cluster organic frameworks made of heptanuclear trigonal-prismatic cluster units.

A series of lanthanide-based cluster organic frameworks, [Ln(7)(μ(3)-OH)(8)L(9)(H(2)O)(6)]·4ClO(4)·3HL·nH(2)O [HL = 4-pyridin-4-ylbenzoic acid; Ln = Y (1), La (2), Gd (3), Yb (6), n = 6; Ln = Dy (4), Er (5), n = 4], were hydrothermally made and characterized. It is the first example of heptanuclear trigonal-prismatic lanthanide clusters via a hydrothermal reaction. The magnetic properties of 3 and 4 show typical antiferromagnetic interactions.

Bandgap Engineering of Titanium–Oxo Clusters: Labile Surface Sites Used for Ligand Substitution and Metal Incorporation

Through the labile coordination sites of a robust phosphonate-stabilized titanium-oxo cluster, 14 O-donor ligands have been successfully introduced without changing the cluster core. The increasing electron-withdrawing effect of the organic species allows the gradual reduction of the bandgaps of the {Ti6 } complexes. Transition-metal ions are then incorporated by the use of bifunctional O/N-donor ligands, organizing these {Ti6 } clusters into polymeric structures. The coordination environments of the applied metal ions show significant influence on their visible-light adsorption. Both the above structural functionalizations also tune the photocatalytic H2 production activities of these clusters. This work provides a systematic bandgap engineering study of titanium-oxo clusters, which is important not only for their future photocatalytic applications, also for the better understanding of the structure-property relationships.

A 3.6 nm Ti52–Oxo Nanocluster with Precise Atomic Structure

We report a 3.6 nm Ti52-oxo cluster with precise atomic structure, which presents a largest size record in the family of titanium-oxo clusters (TOCs). The crystal growth of such large Ti52 is based on a stepwise interlayer assembly approach from Ti6 substructures. The possible growth mechanism of Ti52 could be deduced from crystal structures of two substructures, Ti6 and Ti17, which were also synthesized under similar conditions as Ti52. Moreover, these TOCs show cluster-size-dependent photocatalytic hydrogen evolution activities with Ti52 giving a H2 production rate up to 398 μmol/h/g, which is also the highest record in the family of TOCs. This work not only represents a milestone in constructing large TOCs with comparable sizes as TiO2 nanoparticles but also brings significant advances in improving photocatalytic behaviors of TOCs.

A Series of Vanadogermanates from 1D Chain to 3D Framework Built by Ge–V–O Clusters and Transition-Metal-Complex Bridges

Three novel extended vanadogermanates, {[(en)(2)Cd(2)Ge(8)V(12)O(40)(OH)(8)(H(2)O)][Cd(en)(2)](2)}·6H(2)O (1), {[Zn(2)(dap)(3)][Zn(dap)](2)Ge(6)V(15)O(48)(H(2)O)}[Zn(dap)(2)(H(2)O)](2)·3H(2)O (2), and {[Cd(3)(μ-dien)(2)(Hdien)(2)(H(2)O)(2)]Ge(4)V(16)O(42)(OH)(4)(H(2)O)}·2H(2)O (3; en=ethylenediamine, dap=1,2-diaminopropane, dien=diethylenetriamine), have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, powder XRD, thermogravimetric analysis, and single-crystal XRD. Their Ge-V-O cluster anions are derived from the V(18)O(42) cluster shell by replacing VO(5) square pyramids with Ge(2)O(7) groups. Compound 1 exhibits a 1D sinusoidal chain built up from rare inorganic-organic hybrid dicadmium-substituted vanadogermanate {[Cd(en)](2)V(12)O(40)(GeOH)(8)(H(2)O)} clusters and [Cd(en)(2)] complexes. Compound 2 is the first example of a 2D network based on linkage of the unusual {Ge(6)V(15)O(48)(H(2)O)} clusters and two types of Zn complex fragments. Compound 3 is an unprecedented 3D framework built by {Ge(4)V(16)O(42)(OH)(4)(H(2)O)} clusters and rare trinuclear bridging complex cations [Cd(3)(μ-dien)(2)(Hdien)(2)(H(2)O)(2)](8+). Magnetic measurements illustrate that both 1 and 2 have antiferromagnetic exchange interactions between metal centers, whereas 3 exhibits ferrimagnetic behavior, which is rare in polyoxovanadate complexes.

Two Series of Sandwich Frameworks Based on Two Different Kinds of Nanosized Lanthanide(III) and Copper(I) Wheel Cluster Units

Two series of sandwich frameworks, [La6(μ3-OH)2(ox)3L12Cu11(μ3-X)6(μ2-X)3]·8H2O (X=Br/Cl, FJ-21 a/b; L=4-pyridin-4-yl-benzonate; ox=oxalate) and [Ln4(OAc)3-(H2O)4L9][Cu(μ3-I)]@[Cu10(μ3-I)(μ4-I)6(μ5-I)3]·7H2O (Ln=Pr/Nd/Sm/Eu, FJ-22 a/b/c/d; OAc=acetate) have been hydrothermally prepared. These sandwich frameworks are assembled by two different kinds of nanosized lanthanide-(III) and copper(I) wheel cluster units, La18 and 3Cu@Cu24 in FJ-21, Ln24 and Cu2@Cu24 in FJ-22. The synergistic coordination between organic ligands, L and oxalate/acetate, leads to the formation of La18 and Ln24 wheels, while the synergistic coordination between organic L and inorganic Br/I ligands results in 3Cu@Cu24 and Cu2@Cu24 wheels for FJ-21 and FJ-22, respectively. Thus, two types of synergistic coordination between two different organic ligands, as well as inorganic and organic ligands are simultaneously observed in FJ-21 and FJ-22.

Hydrothermal Combination of Trilacunary Dawson Phosphotungstates and Hexanickel Clusters: From an Isolated Cluster to a 3D Framework

Three novel hexa-Ni-substituted Dawson phosphortungstates [Ni6 (en)3 (H2O)6 (μ3-OH)3 (H3 P2 W15 O56 )]⋅14 H2O (1), [Ni(enMe)2 (H2O)][Ni6 (enMe)3 (μ3-OH)3 (H2O)6 (HP2 W15 O56)]⋅ 10 H2O (2), and [Ni(enMe)2 ]3 [Ni(enMe)2 (H2O)][Ni(enMe)(H2O)2][Ni6 (enMe)3 (μ3-OH)3 (Ac)2 (H2O)(P2 W15 O56)]2 ⋅6 H2O (3) (en=ethylenediamine, enMe=1, 2-diaminopropane, Ac=CH3 COO(-)) have been made under hydrothermal conditions and were characterized by IR spectroscopy, elemental analysis, diffuse reflectance spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The common structural features of compounds 1-3 contain the similar hexa-Ni-substituted Dawson polyoxometalate (POM) units that can be viewed as a [Ni6 (μ3-OH)3](9+) cluster capping on a [P2 W15 O56](12-) fragment. Compounds 1 and 2 are two isolated clusters, whereas compound 3 is the first 3D POM framework constructed from hexa-Ni-substituted Dawson POM units and Ni(enMe) complex bridges. The preparations of compounds 1-3 not only indicate that triangle coplanar Ni6 clusters are very stable fragments in both trivacant Keggin and trivacant Dawson POM systems, but also offer that the hydrothermal technique can act as an effective strategy for making novel Dawson-type high-nuclear transition-metal cluster substituted POMs by combination of lacunary Dawson precusors with transition-metal cations in the tunable role of organic ligands. In addition, magnetic measurements illustrate that there exist overall ferromagnetic interactions in compound 3.

Azole Functionalized Polyoxo-Titanium Clusters with Sunlight-Driven Dye Degradation Applications: Synthesis, Structure, and Photocatalytic Studies.

Six polyoxo-titanium clusters (PTCs) with varying nuclearities containing Ti-N bonds and heteronuclearity, namely, [Ti6(μ3-O)2(μ2-O)2(O3P-Phen)2(OiPr)10(1-hbta)2] (PTC-37), Ti8(μ3-O)2(μ2-O)2(O3P-Phen)2(OiPr)16(adn)2(NO3)2] (PTC-38), [Ti4(μ3-O)(μ2-O)(μ2-OiPr)2(OiPr)4(O3P-Phen)3(1,10-phn)](HOiPr) (PTC-39), [Ti4(μ3-O)(μ2-OiPr)3(OiPr)5(O3P-Phen)3(Im)] (PTC-40), [Ti4(μ3-O)(μ2-OiPr)3(OiPr)5(O3P-Phen)3(Im)][Ti3M(μ3-O)(μ2-OiPr)3(OiPr)3(O3P-Phen)3(Im)] (M = Co for PTC-41 and M = Zn for PTC-42; O3P-Phen = phenyl phosphonate, 1-hbta = 1-hydroxy benzotriazolate, adn = adenine, 1,10-phn = 1,10-phenanthroline, Im = imidazolate, and OiPr = isopropoxide) were prepared as crystalline samples and structurally characterized. Simultaneous doping of nitrogen and transition metal heteroatoms into the Ti-O clusters created complex chemical environments in the resulting hybrid materials. Thus, photocatalytic methylene blue degradation studies were performed to understand structure-property relationships in these Ti cluster-based materials. The complex chemical environment created in these novel molecular clusters had proved to exhibit ligand-dependent photocatalytic activities under normal sunlight. Adenine-functionalized PTC-38 presented moderate activities, while other PTCs all show rapid dye degradation.

Construction of Cluster Organic Frameworks with bnn Hexagonal BN Topologies

Two sandwiched cluster organic frameworks, Eu6 (OH)2 Cu9 I6 L12 (ox)3 ⋅H2 O⋅ClO4 (FJ-23, HL=4-pyridin- 4-yl-benzonic acid, ox=oxalate) and Eu6 Cu7 I7 L12 (OAc)6 (H2 O)2 ⋅2 H2 O (FJ-24, OAc=acetate) with bnn hexagonal BN topologies have been successfully made; these frameworks were assembled by nanosized graphene-like lanthanide wheel clusters and nanoscale trigonal prism metalloligands. The cooperation of small equatorial ligands and axially trigonal prism metalloligands plays a key role in the construction of such 5-connected nets. Furthermore, the thermal stabilities and chiral characteristics were also studied.