Qi-Kai Zhang

A New Transparent Conductor: Silver Nanowire Film Buried at the Surface of a Transparent Polymer

With the emergence of fl exible plastic devices and the scarcity of indium resources, great efforts have been made to develop new fl exible transparent conductors to replace indium tin oxide (ITO), [ 1,2 ] examples including conductive polymers, [ 3,4 ] carbon nanotubes (CNTs), [ 5–8 ] graphene, [ 9 ] metal grids, [ 10 ] and random networks of metallic nanowires. [ 11,12 ] Among these contenders, random silver nanowire (AgNW) networks show optoelectronic performances very close to that of ITO [ 11 , 13 ] and are regarded as the leading candidate material to replace ITO [ 14 ] (Table 1S in Supporting Information). There are two critical issues that currently prohibit AgNW fi lms from large scale applications: AgNW fi lms deposited on bare substrates are highly coarse [ 12 ]

PH-controlled construction of Cu(I) coordination polymers: in situ transformation of ligand, network topologies, and luminescence and UV-vis-NIR absorption properties.

Two new complexes [Cu(I)(3)(L1)I(3)](n) (1, L1 = 2,5-bis(4-pyridyl)-1,3,4-oxadiazole) and [Cu(I)(3)(L2)I(2)](n) (2, L2 = 2,5-bis(4-pyridyl)-1,2,4-triazolate) are controllably formed by using aqueous ammonia to regulate the pH value of the reaction involving CuI and L1. Interestingly, L2 of 2 is in situ generated from the ring transform of L1 when increase the pH value of the reaction. 1 exhibits 2-D layer, while 2 shows 3-D MOFs with a novel 3-nodal 4,4,5-connected net topology of an unprecedented Point (Schlafli) symbol: (4·5(2)·6(2)·7)(5(4)·8(2))(4(3)·5·6(6)). Although both 1 and 2 are built of CuI and similar ligands, different arrangements of CuI chains and ligands endow them with different physical properties. 1 displays a strong pure red luminescence emission, while 2 is nonluminescent and shows a broad absorption band covering the whole UV-vis-NIR spectrum range. The emissive excited states of 1 and the charge transitions of the optical absorption for 2 are solved by DFT calculations.

Stoichiometry, temperature, solvent, metal-directed syntheses of metal–organic frameworks based on flexible V-shaped methylenebis(3,5-dimethylpyrazole) and various aromatic dicarboxylate acids

Seven new metal–organic frameworks (MOFs), namely, {[Cd2(NDC)2(H2MDP)](H2O)} (1), [Cd(NDC)(H2MDP)] (2), {[Cd2(NDC)(HNDC)2(H2MDP)2](H2O)0.5} (3), [Cd(NH2–BDC)(H2MDP)2] (4), [Cd(NH2–BDC)(H2MDP)2] (5), [Cd(H2MDP)(Br–BDC)0.5(Br–HBDC)] (6), {[Co(H2MDP)(Br–BDC)](H2O)0.5} (7) (H2MDP = methylenebis(3,5-dimethylpyrazole), H2NDC = 1,4-naphthalenedicarboxylic acid, NH2–H2BDC = 2-amino-1,4-benzenedicarboxylic acid, Br–H2BDC = 2,5-dibromo-1,4-benzenedicarboxylic acid) have been controllably synthesized with H2MDP and different aromatic dicarboxylic acids by tuning metal-to-ligand molar ratios, temperature, solvents and metal ions. Compound 1 is a 3D 2-fold interpenetrated pcu framework of 412·63 topology constructed from paddle-wheel SBUs and trans-conformation H2MDP pillars, while compound 2 exhibits a 3D 3-fold interpenetrated diamondoid framework formed by single metal nodes via linear NDC2− and trans-conformation H2MDP ligands. Interestingly, compound 3 contains two different types of binuclear subunits formed by a pair of Cd(II) ions with partly deprotonated HNDC− ligands, and these subunits are further linked by completely deprotonated NDC2− and cis-conformation H2MDP ligands to form a 2D (4,4) network. Compounds 4 and 5 are solvent-induced structural isomers based on 2D (4,4) layers, and therefore have different solvent-accessible voids. Compounds 6 and 7, synthesized with different metal salts under similar solvothermal conditions, are characteristic of a 3D hydrogen-bonded supramolecular network, and a 3D 3-fold interpenetrated diamondoid network with equal number of left- and right-handed helical {Cd(H2MDP)}n chains further bridged together by linear Br–BDC2− ligands, respectively. In addition, the luminescent properties of solids 1–6 have been investigated at room temperature.

Highly efficient cuprous complexes with thermally activated delayed fluorescence and simplified solution process OLEDs using the ligand as host

Two strongly luminescent complexes, [Cu(czpzpy)(PPh3)]BF4 (1) and [Cu(czpzpy)(POP)]BF4 (2), bearing a new carbazole-based diimine ligand (czpzpy = 2-(9H-carbazolyl)-6-(1H-pyrazolyl)pyridine, PPh3 = triphenylphosphine, and POP = bis[2-(diphenylphosphine)phenyl]ether) were synthesized and characterized. Complex 2 emits intense thermally activated delayed fluorescence (TADF) with high photoluminescence quantum yields (PLQYs) of up to 0.98 at room temperature in the solid state. A highly efficient solution-processed OLED, with an emissive layer was spin-coated using a mixture of the diimine ligand czpzpy and the starting material, [Cu(CH3CN)2)(POP)]BF4, was fabricated with peak efficiencies of 6.36% (external quantum efficiency, EQE) and 17.53 cd A−1 (current efficiency, CE) and a maximum brightness of 3251 cd m−2. These performances are nearly identical to those of the device whose emissive layer was comprised of complex 2 and czpzpy, indicating that this simplified process, which omits the preparation and purification of the emissive complex, is practicable in preparing efficient solution-processed OLEDs. In this approach, czpzpy, which bears a carbazole unit, was used both as a ligand to form the emissive cuprous complex and as a host matrix for the formed emitter.

A 2D polyoxometalate-based complex: spin-canting and metamagnetism

A novel polyoxometalate-based complex [Cu2(ptz)(H2O)(μ2-O)(Mo4O13)]·H2O (ptz= 5-(2-pyridyl)tetrazole) was synthesized using a hydrothermal method; it exhibits a two-dimensional network structure and the concomitant existence of spin canting and metamagnetism.

Syntheses, structures, and photoluminescent properties of ten metal–organic frameworks constructed by a flexible tetracarboxylate ligand

Reactions of zinc ions with the flexible tetracarboxylate ligand, 5,5′-(1,4-phenylenebis(methylene))bis(oxy)diisophthalic acid (H4L1) gave rise to ten complexes, namely {[Zn3(L1)(OH)2(H2O)2]3H2O}n (1), {[Zn(H2L1)(H2O)2]H2O}n (2), [Zn2(L1)(H2O)4]n (3), {[Zn2(H3L1)2(H2L1)(H2O)2(MeCN)2]}n (4), [Zn2(H3L1)2(H2L1)(2,2′-bipy)2]n (5), [Zn2(H3L1)2(H2L1)(1,10-phen)2]n (6), {[Zn2(L1)(4,4′-bipy)2]4H2O}n (7), {[Zn2(L1)(bpe)2]4H2O}n (bpe = 1,2-bi(4-pyridyl)ethene) (8), {[Zn2(L1)(pdp)2]4H2O}n (pdp = 4-[(E)-4-Pyridinylazo]pyridine) (9) and {[Zn2(L1)(bpmp)2]6H2O}n (bpmp = N,N′-bis-(4-pyridyl-methyl) piperazine) (10). The H4L1 ligand not only displayed different deprotonated forms, but also diverse coordination modes and conformations. Compounds 1–4 are constructed of only zinc atoms with H4L1 ligands while compounds 5–10 are constructed of zinc atoms and H4L1 ligands with various N-donor ligands (Scheme 1). Compound 1 features a 3D architecture constructed of a linear Zn3 cluster with H4L1 ligands. Compound 2 is a 2D waved layer structure with (4,4) grid as sql topology. Compound 3 displays a three-dimensional (3D) network simplified by a (3,6)-connected 2-nodal net with ant topology. Compounds 4, 5 and 6 all exhibit 1D infinite chains coordination structure, in which the H4L1 ligand is displayed as two kinds of deprotonated forms. Compounds 7, 8, 9 and 10 are similar and possess (4,4)-connected 3D frameworks with bbf topology, while also exhibiting an intriguing three-fold interpenetrated structure. These results indicate that subtle environmental factors, such as solvent, pH value and neutral auxiliary ligands play important roles in the formation of the structures of the final framework. At the same time, the photochemical properties of compounds 1–10 were tested in the solid state at room temperature, and the luminescent properties of compound 9 and 10 when dispersed in different solvents were investigated. These showed solvent-dependent luminescent spectra with emission intensities significantly quenched towards nitrobenzene. The quenching effects are observed at a low nitrobenzene concentration of 200 ppm, which indicates high sensitivities of these compounds towards nitrobenzene.

Novel ladder-type heteroheptacene-based copolymers for bulk heterojunction solar cells

Four semiconducting copolymers were designed and synthesized based on a novel ladder-type heteroheptacene building block, which was prepared in four steps from 3,7-dibromodibenzo[b,d]thiophene. The copolymers were characterized by 1H NMR spectroscopy, UV-Vis absorption spectroscopy, cyclic voltammetry and their molecular weights were estimated using gel permeation chromatography. Field effect transistors (FETs) fabricated from these four polymers exhibit semiconducting behavior in air. The highest mobility of 2.21 × 10−4 cm2 V−1 s−1 was found in the polymer copolymerized from the ladder-type heteroheptacene and terthiophene. Low band-gap donor–acceptor copolymers with a deep-lying HOMO energy level were synthesized by a copolymerization between the ladder-type heteroheptacene donor and the 2,1,3-benzothiadiazole acceptor. Polymer solar cells made from one of these polymers gave a power conversion efficiency of 4.17%, a current density of 9.2 mA cm−2, an open-circuit voltage of 0.79 V, and a fill factor of ∼57.4% under 100 mW cm−2 AM 1.5 G sunlight illumination.

Auxiliary ligand-directed synthesis of a series of Cd(II)/Co(II) coordination polymers with methylenebis(3,5-dimethylpyrazole): syntheses, crystal structures, and properties

Using a flexible methylenebis(3,5-dimethylpyrazole) ligand (H2MDP) with different aromatic carboxylate ligands, six new complexes {[Cd(H2MDP)(OPh)](H2O)}n (1), {[Cd(H2MDP)(MPh)](H2O)(1/10)}n (2), {[Cd(H2MDP)(PPh)](H2O)(3/2)}n (3), {[Co(H2MDP)(OPh)](H2O)2}n (4), {Co(H2MDP)(MPh)}n (5), {Co(H2MDP)(HBTC)}n (6) (H2OPh = phthalic acid, H2MPh = isophthalic acid, H2PPh = terephthalic acid, H3BTC = benzene-1,3,5-tricarboxylic acid) have been isolated under hydrothermal conditions. The crystal structure analyses reveal that complexes 1 and 4 feature two-dimensional undulated sheets with 4(4)·6(2) topology. Both complexes 2 and 3 contain M2L2-type metallocyclic motifs composed of two H2MDP ligands and two metal atoms, while complex 2 features a two-dimensional 4(4)·6(2) network constructed from binuclear cadmium units as four connected nodes, and complex 3 shows a two-dimensional network with 6(3)-hcb topology. Complex 5 affords a one-dimensional chain structure, and complex 6 shows a two-dimensional (4,4) network further connected into a 3D supramolecular structure connected by intermolecular hydrogen bonds and by π-π interactions. In addition, the luminescent properties of complexes 2 and 3 as well as the magnetic properties of 4 and 5 were studied.

Construction of coordination polymers based on methylenebis(3,5-dimethylpyrazole) and varied aromatic carboxylic acids

Six new coordination polymers, namely, [Co(Cl-BDC)(H2MDP)]·0.5H2O (1), [Cd(Cl-BDC)(H2MDP)] (2), [Cd(OH-ip)(H2MDP)2]·H2O (3), [Mn(NO2-ip)(H2MDP)(H2O)] (4), [Cu(BTEC)1/2(H2MDP)] (5), and [Co(BTEC)1/2(H2MDP)]·H2O (6) (H2MDP = methylenebis(3,5-dimethylpyrazole), Cl-H2BDC = 2,5-dichloroterephthalic acid, OH-H2ip = 5-hydroxy-1,3-benzenedicarboxylic acid, NO2-H2ip = 5-nitro-1,3-benzenedicarboxylic acid, H4BTEC = 1,2,4,5-benzenetetracarboxylic acid) have been hydrothermally synthesized by using H2MDP as the main ligand and varying aromatic acids as auxiliary ligands, and characterized by single-crystal X-ray structure determination, FT-IR, elemental analysis, and powder X-ray diffraction. It was found that in complexes 2, 3, 4, and 6 the H2MDP ligands adopt a cis-conformation and tend to form M2L2-type metallocyclic units (SBU-1). These metallocyclic units further serve as linkers to connect the {metal–aromatic carboxylate}n chains to form two-dimensional frameworks with different structural features and topologies, i.e. 2D 63-hcb network for 2, (4,4) net for 3, undulated 63-hcb layered framework for 4, and dual (3,4)-connected net for 6 with point (Schlafli) symbol of (4·62)2(42·62·82). In complexes 1 and 5, the H2MDP ligands adopt a trans-conformation, and tend to link {metal–aromatic carboxylate}n chains into a higher dimensional framework, i.e. 3D triply interpenetrated dia network for 1 and dual (4,4)-connected double-layered structure for 5 with point (Schlafli) symbol of (54·62)(55·81)2. Moreover, the magnetic properties of complexes 1 and 6, and photoluminescent properties of 3 have also been investigated.

Synthesis and Characterization of Ferrocene Derivatives and Preliminarily Electrocatalytic Oxidation of L-Cysteine at Nafion-Ferrocene Derivatives Modified Glassy Carbon Electrode

Five new structural ferrocene derivatives (2a~2e) were firstly synthesized and characterized by 1H NMR, 13C NMR, ESI-MS, and XRD. Subsequently, the preliminarily electrocatalytic oxidation of L-cysteine (L-Cys) at nafion-ferrocene derivatives modified glassy carbon electrode (GCE) has also been investigated by cyclic voltammetry. The results showed that 2e can dramatically electrocatalyze the oxidation of L-cysteine at its modified GCE in 0.1 mol L−1 NaNO3 aqueous solution with a quasireversible process with mV.