Ji-Cheng Ma

A series of 1D, 2D and 3D coordination polymers based on a 5-(benzonic-4-ylmethoxy)isophthalic acid: syntheses, structures and photoluminescence

Seven new coordination polymers, namely, [Zn(HL)(H2O)] (1), [Zn(HL)(phen)]·1.5H2O (2), [Zn(HL)(L1)] (3), [Zn2(HL)2(L2)2]·2H2O (4), [Zn(HL)(L3)0.5] (5), [Zn(HL)(L4)] (6) and [Cu2(L)(OH)(H2O)]·0.5H2O (7) (H3L = 5-(benzonic-4-ylmethoxy) isophthalic acid, phen = 1,10-phenathroline, L1 = 1,2-bis(1,2,4-triazole-1-yl)ethane, L2 = 1,3-bis(1,2,4-triazole-1-yl)propane, L3 = 1,6-bis(1,2,4-triazole-1-yl)hexane and L4 = 4,4′-bis(1,2,4-triazole-1-ylmethyl)biphenyl), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. In compounds 1–6, the H3L ligand is partially deprotonated to form HL2−, while it is completely deprotonated in 7. Compound 1 shows a 3D framework with 4-connected (42·7·83)2 topology. Compound 2 displays a 1D ribbon structure. The neighboring ribbons are further linked by hydrogen-bonding interactions to form a 3D supramolecular architecture. Compound 3 exhibits a 2D undulated sheet. The sheets are further penetrated into each other to give rise to a 3D polycatenation structure. Compound 4 displays a 2D supramolecular layer structure. Compound 5 shows a 3D (3,6)-connected (4·8)(4·82·103) net. Compound 6 reveals a 3D four-fold interpenetrating diamondoid architecture. Compound 7 displays a (3,8)-connected (4·62)(44·68·812·104) topology. These compounds have been characterized by powder X-ray diffractions (PXRD) and thermal gravimetric analyses (TGA). In addition, the photoluminescent behaviours of 1–6 have been investigated in detail.

Versatile frameworks constructed from divalent metals and 1,2,3,4-butanetetracarboxylate anion: syntheses, crystal structures, luminescence and magnetic properties

Nine new coordination polymers, namely [Cu(BTCA)0.5(H2O)3]·2H2O (1), [Ni2(BTCA)(H2O)5]·2H2O (2), [Zn(BTCA)0.5(H2O)2]·0.5H2O (3), [Mn(BTCA)0.5(bipy)(H2O)] (4), [Mn(BTCA)0.5(phen)(H2O)] (5), [Zn(BTCA)0.5(obib)]·2.5H2O (6), [Zn(BTCA)0.5(pbib)0.5]·H2O (7), [Zn(BTCA)0.5(bbi)]·H2O (8) and [Co(BTCA)0.5(bbi)]·H2O (9), where bipy = 2,2′-bipyridine, phen = 1,10-phenathroline, obib = 1,2-bis(imidazol-1-ylmethyl)benzene, pbib = 1,4-bis(imidazol-1-ylmethyl)benzene, bbi = 1,1′-(1,4-butanediyl)bis(imidazole), and BTCA = 1,2,3,4-butanetetracarboxylate anions, were synthesized. Compounds 1 and 2 possess 2D polymeric structures, while compound 3 has a 3D network. Compounds 4 and 5 exhibit infinite 1D chain structures, and the adjacent chains are connected through π–π interactions between the aromatic rings of bipy or phen ligands. Both of the 3D frameworks of 6 and 7 are built from 2D zinc-carboxylate layers stretched by bis(imidazole) ligands. Compounds 8 and 9 are isostructural and show 3-fold interpenetrated α-Po structures. The thermal stabilities of 1–9 were studied by thermogravimetric analysis. The luminescent properties for 6–8 in the solid states, and magnetic property for 9 are also discussed in detail.

Performance improvement of resistive switching memory achieved by enhancing local-electric-field near electromigrated Ag-nanoclusters

By introducing Ag nanoclusters (NCs), ZnO-based resistive switching memory devices offer improved performance, including improved uniformity of switching parameters, and increased switching speed with excellent reliability. These Ag NCs are formed between the top-electrode (cathode) and the switching layer by an electromigration process in the initial several switching cycles. The electric field can be enhanced around Ag NCs due to their high surface curvature. The enhanced local-electric-field (LEF) results in (1) the localization of the switching site near Ag NCs, where oxygen-vacancy-based conducting filaments have a simple structure, and tend to connect Ag NCs along the LEF direction; (2) an increase in migration and recombination rates of oxygen ions and oxygen vacancies. These factors are responsible for the improvement in device performance.

Structures of metal-organic networks based on flexible 1,1′-(1,4-butanediyl)bis(imidazole-2-phenyl) ligand

A new neutral ligand 1,1′-(1,4-butanediyl)bis(imidazole-2-phenyl) (bbip) and six coordination polymers, namely [Zn(o-bdc)(bbip)]·H2O (1), [Zn(m-bdc)(bbip)]·H2O (2), [Cd(m-bdc)(bbip)] (3), [Zn(OH–bdc)(bbip)] (4), [Cd(OH–bdc)(bbip)] (5) and [Zn(fum)(bbip)]·H2O (6) (where o-H2bdc = 1,2-benzenedicarboxylic acid, m-H2bdc = 1,3-benzenedicarboxylic acid, OH–H2bdc = 5-hyroxyisophthalic acid and H2fum = fumaric acid), are described. Compound 1 shows a one-dimensional double-stranded chain structure. Compounds 2 and 4 possess 2D polymeric layers, and the layers are connected through van der Waals forces and hydrogen bonds into 3D supramolecular structures, respectively. Compounds 3, 5 and 6 exhibit 3-fold interpenetrating diamondoid networks. The luminescent properties for these compounds in the solid state are discussed.

Effect of oxygen-related surface adsorption on the efficiency and stability of ZnO nanorod array ultraviolet light-emitting diodes

Ultraviolet light-emitting diodes using MgZnO-coated and bare ZnO nanorod arrays as active layers were manufactured. Both types were exposed to ambient air over a 1-yr period to assess their stability. By monitoring the electroluminescence evolution with air-exposure time and comparing the changes of electroluminescence and x-ray photoelectron spectra before and after vacuum desorption, it is concluded that surface-adsorbed O2 and OH− species, as acceptor and donor surface states, quench ultraviolet electroluminescence, and favor undesirable surface-mediated nonradiative and deep-level recombination. The MgZnO coating prevents surface adsorption, and so the coated nanorod device shows higher efficiency and stability than the uncoated one.

Four novel topological frameworks based on 4,4′-(hexafluoroisopropylidene)diphthalic acid and 1,1′-(1,4-butanediyl)bis(imidazole) ligand

Four new coordination polymers, constructed from 4,4′-(hexafluoroisopropylidene)diphthalic acid (H4L) and 1,1′-(1,4-butanediyl)bis(imidazole) (biim-4) ligand, have been synthesized: [Cd(HL)(Hbiim-4)(biim-4)0.5(H2O)]·2H2O (1), [Cd2(L)(biim-4)0.5(H2O)2]·0.5H2O (2), [Mn2(L)(biim-4)0.5(H2O)2]·0.5H2O (3), and [Zn2(L)(biim-4)1.5]·(CH3CH2OH) (4), where H4L = 4,4′-(hexafluoroisopropylidene)diphthalic acid, and biim-4 = 1,1′-(1,4-butanediyl)bis(imidazole). Compound 1 displays a 1D chain structure, which is extended by intermolecular hydrogen-bonding interactions to give a novel trinodal (4,5)-connected (4·64·8)(42·63·8)(43·64·83) topology. Compounds 2 and 3 are nearly isostructural with the same uncommon (5,6)-connected frameworks. Compound 4 shows an unprecedented self-penetrating (4,5)-connected net with Schlafli symbol of (42·6·72·8)(62·72·82)(42·63·73·82). The structural and topological differences of these four compounds indicate that the pH values and the central metals have significant effects on producing novel structures and topologies of the coordination complexes. The thermogravimetric and photoluminescent properties were also investigated for the compounds.

ZnO ultraviolet random laser diode on metal copper substrate

Direct fabrication of light emitting devices on metal substrates is highly desirable due to their advantages of high thermal conductivity and light reflection. In this work, we demonstrated a feasibility of directly fabricating ZnO-based ultraviolet laser diodes on metal substrates. By introducing an anti-oxidation buffer layer, Au/MgO/ZnO metal-insulator-semiconductor heterojunction devices are successfully fabricated on the copper substrate. Electrically pumped ultraviolet random lasing was achieved from ZnO active layer. The use of copper substrate offers some merits, including lower thermal effect and higher stability of emission wavelength.

Four silver-containing coordination polymers based on bis(imidazole) ligands

Four coordination polymers, [Ag(L1)](m-Hbdc) (1), [Ag(L1)]2(p-bdc) · 8H2O (2), [Ag(Hbtc)(L1)][Ag(L1)] · 2H2O (3) and [Ag2(L2)2](OH-bdc)2 · 4H2O (4), where L1 = 1,1′-(1,4-butanediyl)bis(imidazole), L2 = 1,2-bis(imidazol-1-ylmethyl)benzene, m-H2bdc = 1,3-benzenedicarboxylic acid, p-H2bdc = 1,4-benzenedicarboxylic acid, H3btc = 1,3,5-benzenetricarboxylic acid, and OH–H2bdc = 5-hydroxisophthalic acid, were synthesized under hydrothermal conditions. Compound 1 contains a–Ag-L1–Ag-L1–chain and a hydrogen-bonding interaction induced–(m-Hbdc)-(m-Hbdc)–chain. Compound 2 consists of two independent–Ag-L1–Ag-L1–chains. P-bdc anions are not coordinated. Hydrogen bonds form a 3D supramolecular structure. A novel (H2O)16 cluster is formed by lattice water molecules in 2. Compound 3 contains a–Ag-L1–Ag-L1–and a–Ag(Hbtc)-L1–Ag(Hbtc)-L1–chain. The packing diagram shows a 2D criss-cross supramolecular structure, with π ··· π and C–H ··· π interactions stabilizing the framework. Compound 4 contains a [Ag2(L2)2]2+ dimer with hydrogen-bonding, π ··· π, and Ag ··· O interactions forming a 3D supramolecular framework. The luminescent properties for these compounds in the solid state are discussed.

Two non-interpenetrating 3D coordination networks with (3, 4)-connected topologies

Two new coordination polymers, namely [Zn3(1,3,5-BTC)2(L1)2(H2O)2] · 2H2O (1) and [Cd3(1,2,3-BTC)2(L2)3] · H2O (2) (where L1 = 1,2-bis(imidazol-1-ylmethyl)benzene, L2 = 1,1′-(1,4-butanediyl)bis(imidazole), 1,3,5-H3BTC = 1,3,5-benzenetricarboxylic acid and 1,2,3-H3BTC = 1,2,3-benzenetricarboxylic acid), were synthesized in hydrothermal conditions. In 1, each 1,3,5-BTC anion coordinates to three Zn cations, and the framework of 1 can be simplified as (6 · 8 · 10)2(62 · 8 · 103)(82 · 10)(62 · 10) topology. In 2, 1,2,3-BTC anions coordinate to three cadmiums, and the whole structure displays a (62 · 84)2(64 · 8 · 10)(62 · 8)2 network containing three different types of nodes. The luminescent properties for 1 and 2 are discussed.

A series of lanthanide-transition metal coordination polymers with mixed ligands: syntheses, structures, photoluminescence and magnetic properties

Six unusual lanthanide-transition metal compounds, [Ln2M(1,3-bdc)4(TPA)(H2O)]·nH2O (n = 2, Ln = Y, M = Co 1; n = 2, Ln = Y, M = Zn 2; n = 2, Ln = Er, M = Co 3; n = 2, Ln = Er, M = Zn 4; n = 0.5, Ln = Sm, M = Co 5) and [Y2Ni2(1,3-bdc)5(TBA)(H2O)3]·7H2O 6, where 1,3-H2bdc = benzene-1,3-dicarboxylic acid, TPA = tris(2-pyridylmethyl)amine and TBA = tris(2-benzimidazolylmethyl)amine, have been synthesized under hydrothermal conditions. Their structures have been determined by single-crystal X-ray diffraction analyses. Compounds 1–5 are isomorphous, and crystallize in the space groupP21/c. In 1–5, the Ln atoms are connected by 1,3-bdc anions to form 2D layer structures, where the terminal M(TPA)(1,3-bdc) units are attached to both sides of the 2D layers. In compound 6, the Y atoms are connected by 1,3-bdc anions to form a 1D double chain structure. In addition, the photoluminescence and variable-temperature magnetic susceptibility of the compounds have been studied.