ai-Ming Hu

A novel 1D armed-polyrotaxane chain constructed from a V-shaped tetracarboxylate ligand

A novel armed-polyrotaxane, comprising two interpenetrating chains of rings with arms, is self-assembled from the flexible ligands 3,3′,4,4′-diphenylsulfonetetracarboxylic acid, as an annular linker motif, and 1,2-di(4-pyridyl)ethylene, as linking rods, which further assembles into a 2D ladder network through hydrogen bonding interactions.

Four novel Zn(II)/Cd(II) metal–organic frameworks constructed from 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine: hydrothermal synthesis, crystal structures, and luminescent properties

Four novel polymeric frameworks, [Zn(pytpy)Cl2]n (1), [Zn2(pytpy)2(ox)2]n·n(H2O) (2), [Cd(pytpy)(mal)]n·n(H2O) (3) and [Zn2(pytpy)(btc)(OH)]n (4), (pytpy = 4′-(4-pyridyl)-4,2′:6′,4″-terpyridine, H2ox = oxalic acid, H2mal = malic acid and H3btc = 1,3,5-benzenetricarboxylic acid) have been hydrothermally synthesized and structurally characterized. Compound 1 shows infinite helical chains, which are extended into a 3D supramolecular network by intermolecular hydrogen bonds. In the structure of 2, there is coexistence of left- and right-handed helical chains arranged alternately to generate a 2D layer. In 3, an in-situ reaction occurred, maleic acid was converted to malate by the hydroxylation of the ethylene group to prepare the microporous architecture. Compound 4 is a two-fold interpenetrating 3D ploymeric network with an intriguing topological structure. The luminescence properties of 1–4 have been investigated with fluorescence emission spectra and the UV-vis diffuse reflectance spectra in the solid state. Additionally, these four compounds possess great thermal stabilities, especially for 2, the framework is stable up to 400 °C.

Effect of pH/metal ion on the structure of metal–organic frameworks based on novel bifunctionalized ligand 4′-carboxy-4,2′:6′,4′′-terpyridine

Four novel coordination polymers, [Cd2(ctpy)4]n·2nH2O (1), [Cd2(ctpy)2(ox)]n (2), [Zn(ctpy)(ox)0.5]n·0.5nH2O (3) and [Cu2(ctpy)2(ox)]n (4), (Hctpy = 4′-carboxy-4,2′:6′,4′′-terpyridine H2ox = oxalic acid), have been hydrothermally synthesized and characterized by elemental analysis, IR, single crystal X-ray diffraction and thermogravimetric analyses. Compound 1 is a new two-fold interpenetrating (3,5)-connected 3D framework with Schlafli symbol (63)(69·8). Compound 2 displays an unusual three-dimensional coordination network which exhibits an intriguing (4,5)-connected binodal new topological net with Schlafli symbol (42·63·8)(42·65·83). Compound 3 features a two-fold interpenetrating (3,4)-connected 3D framework with the fsc topological net and the Schlafli symbol (63)(65·8). Compound 4 is a three-fold interpenetrating (3,4)-connected 3D framework with dmc topological net and Schlafli symbol (4.82)(4.85). Interestingly, compounds 1–4 were obtained under similar reaction conditions. The structural diversity of compounds 1 and 2 may illustrate the marked effect of pH on the reaction solution. And the diversity structures of the compounds 2–4 may illustrate the marked effect of the metal ion on the reaction solution. Moreover, the fluorescent property of compounds 1–3 as well as the adsorption properties of 3 are also investigated.

Synthesis, Structure, White-Light Emission, and Temperature Recognition Properties of Eu/Tb Mixed Coordination Polymers.

Two series of Eu(III)/Tb(III) coordination polymers, [LnL(glu)]n·2nH2O (Ln = Eu (1), Tb (2)) and [LnL(glu)(H2O)]n (Ln = Eu (3), Tb (4)) [HL = (2-(2-sulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline, H2glu = glutaric acid] have been hydrothermally synthesized by controlling the pH values and characterized by elemental analysis, infrared spectra, and single-crystal X-ray diffraction. Isomorphic compounds 1 and 2 exhibit 6-connected 3D network with the pcu topological net, containing left- and right-handed helical chains. Isomorphic compounds 3 and 4 show 3,4-connected 2D new topology with the point symbol of (4(2)·6(3)·8)(4(2)·6). Multicolor luminescence can be tailored from red to green regions by singly varying the mixing molar ratio of Eu(III)/Tb(III) cations. The mixing component of 1Eu/2Tb = 4:6 not only achieves white-light emission with the CIE coordinate of (0.323, 0.339) upon excitation at 405 nm but also presents a temperature recognition property with the significantly high sensitivity of 0.68% per K in the 50-225 K temperature range upon excitation at 370 nm.

Three Banana-Shaped Arsenomolybdates Encapsulating a Hexanuclear Transition-Metal Central Magnetic Cluster: [AsIII2FeIII5MMo22O85(H2O)]n− (M = Fe3+, n = 14; M = Ni2+ and Mn2+, n = 15)

Three polyoxometalates encapsulating high-nuclearity magnetic clusters MFe(5), [As(2)MFe(5)Mo(22)O(85)(H(2)O)](n-) (M = Fe(3+), n = 14; M = Ni(2+) and Mn(2+), n = 15), were synthesized and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, thermogravimetric analysis, and magnetism measurements. The polyanion [As(2)MFe(5)Mo(22)O(85)(H(2)O)](n-) consists of a central MMo(7)O(28) (M = Fe(3+), Ni(2+), and Mn(2+)) fragment and two AsMo(7)O(27) fragments linked together by two trimeric clusters, Fe(2)MoO(μ(2)-O)(2) and Fe(3)(H(2)O), to form a banana-shaped structure with C(1) symmetry. The MMo(7)O(28) and AsMo(7)O(27) units have a similar structure and can be considered as a monocapped hexavacant α-B-Keggin subunit with a central MO(4) group or a central As(III)O(3) group. The polyoxometalates have a low absorption of υ(Mo-O(d)) (925-913 cm(-1)) because most of the Mo atoms in the polyanions have at least two longer Mo-O(d) bonds. The framework of the arsenomolybdates is stable before As(2)O(3) escaping (ca. 300 °C). The analysis of magnetostructural correlations and magnetism measurements indicate the coexistence of ferro- and antiferromagnetic interactions, which give an overall ferromagnetic spin ground state in the compounds.

Two sandwich arsenomolybdates based on the new building block As(iii)Mo(7)O(27)(9-): [Cr(2)(AsMo(7)O(27))(2)](12-) and [Cu(2)(AsMo(7)O(27))(2)](14-).

The polyanions [Cr(2)(AsMo(7)O(27))(2)](12-) () or [Cu(2)(AsMo(7)O(27))(2)](14-) () have sandwich-like structures wrapping two transition metals between two [As(iii)Mo(7)O(27)](9-) fragments, and the fragment is unprecedented and can be viewed as a mono-capped hexavacant B-alpha-Keggin subunit with a central AsO(3) group.

An unusual asymmetric polyoxomolybdate containing mixed-valence antimony and its derivatives: [Sb4VSb2IIIMo18O73(H2O)2]12- and {M(H2O)2[Sb4VSb2IIIMo18O73(H2O)2]2}22- (M = MnII, FeII, CuII or CoII).

A new type of heteropolyanion containing mixed-valence antimony, [Sb4(V)Sb2(III)Mo18O73(H2O)2](12-) (1a), and its four derivatives, {M(H2O)2[Sb4(V)Sb2(III)Mo18O73(H2O)2]2}(22-) (M = Mn(II), Fe(II), Cu(II), or Co(II)) (2a-5a), have been isolated as ammonium salt, and their structures were determined by single-crystal X-ray diffraction. The framework of the polyanion 1a displays a curious asymmetric structure, and there exist six types of Sb coordination environments and seven types of {MoO6} octahedra. The title compounds were also characterized by elemental analyses, IR, UV-vis, Raman spectra, and cyclic voltammogramms.

Syntheses, crystal structures and luminescence of 2,6- bis - (5-phenyl-1H-pyrazol-3-yl)pyridine and its d10 metal complexes

A new bis-pyrazole derivative, 2,6-bis-(5-phenyl-1H-pyrazol-3-yl) pyridine (H2BPPP), and two d10 metal complexes [Zn(H2BPPP)Cl2](DMF)2 (1), [Cd(H2BPPP)Cl2](DMF)2 (2) have been synthesized and characterized. There is a tautomeric equilibrium of the bis-pyrazole compound in solution and the H atom of pyrazolyl NH can transfer to the adjacent N atoms. X-ray structure analyses reveal the H atom is on the 2-position of pyrazolyl ring in donor solvents, while the H atom is on the 1-position of pyrazolyl ring in metal complexes. The luminescence of the ligand and complexes have been investigated.

Double Sandwich Polyoxometalate and Its Fe(III) Substituted Derivative, [As2Fe5Mo21O82]17– and [As2Fe6Mo20O80(H2O)2]16–

A double sandwich polyoxometalate and its Fe(III) substituted derivative, [As(2)Fe(5)Mo(21)O(82)](17-) (1) and [As(2)Fe(6)Mo(20)O(80)(H(2)O)(2)](16-) (2), were synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy, fluorescent spectroscopy, UV spectra, thermogravimetry-differential scanning calorimetry analyses, electrospray ionization mass spectrometry, and magnetism measurements. The polyoxoanion is composed of a central fragment FeMo(7)O(28) for 1 (Fe(2)Mo(6)O(26)(H(2)O)(2) for 2) and two external AsMo(7)O(27) fragments linked together by two distinct edge-sharing dimeric clusters Fe(2)O(10) to lead to a C(2v) molecular symmetry. The central FeMo(7)O(28) fragment and external AsMo(7)O(27) fragment have a similar structure, and both of them can be viewed as a monocapped hexavacant α-Keggin subunit with a central FeO(4) group or a central AsO(3) group. Both of the polyoxoanions contain a oxo-bridged Fe(III)(5) magnetic core with the angles of Fe-O-Fe in the range of 96.4(4)-125.7(5)°, and magnetism measurements show an overall ferromagnetic interactions among the five-nuclearity cluster Fe(5) with the spin ground state S = 15/2.

A cagelike polyanion with a Ag+ enwrapped, [AgAs2Mo15O54]11-.

The polyanion [AgAs(2)Mo(15)O(54)](11-) has an unusual cage-like structure composed of [AsMo(6)O(27)](15-) and [AsMo(6)O(24)](9-) subunits connected by three MoO(4) tetrahedra, and a Ag(+) cation is inclosed at the center of the cage and coordinated by two As atoms with a As-Ag-As bond angle of 180° along with three μ(3)-oxo groups from MoO(4) tetrahedra to lead to a trigonal-pyramidal coordination geometry. The compound was also characterized by IR, X-ray photoelectron spectroscopy, fluorescent spectroscopy, and thermogravimetry-differential scanning calorimetry. The stability of [AgAs(2)Mo(15)O(54)](11-) in aqueous solution was investigated by using electronic absorbance spectroscopy and electrospray ionization mass spectrometry.