Qisheng Zhang

New optical supramolecular compound constructed from a polyoxometalate cluster and an organic substrate

A new optical supramolecular compound constructed from a polyoxometalate cluster and an organic substrate [(H3O)(C12H10N3)2(PW12O40)] (1) has been synthesized via a hydrothermal reaction and has been structurally characterized by X-ray diffraction. The solid-state diffuse reflectance, IR, and photoluminescence spectra of the title compound indicate that there is an interaction between the alpha-PW12O40 and the organic substrate. The light-yellow title compound shows a certain second-order nonlinear optical response of I(2omega) = 2I(KDP)(2omega).

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.

Controlling Synergistic Oxidation Processes for Efficient and Stable Blue Thermally Activated Delayed Fluorescence Devices

Efficient sky-blue organic light-emitting diodes (OLEDs) employing thermally activated delayed fluorescence (TADF) display a three orders of magnitude increase in lifetime, which is superior to those of controlled phosphorescent OLEDs used in this study. The combination of electro-oxidation and photo-oxidation of the TADF emitters in their triplet excited-states is suppressed through molecule design and device engineering.

Thermally activated delayed fluorescence from 3nπ* to 1nπ* up-conversion and its application to organic light-emitting diodes

Intense nπ* fluorescence from a nitrogen-rich heterocyclic compound, 2,5,8-tris(4-fluoro-3-methylphenyl)-1,3,4,6,7,9,9b-heptaazaphenalene (HAP-3MF), is demonstrated. The overlap-forbidden nature of the nπ* transition and the higher energy of the 3ππ* state than the 3nπ* one lead to a small energy difference between the lowest singlet (S1) and triplet (T1) excited states of HAP-3MF. Green-emitting HAP-3MF has a moderate photoluminescence quantum yield of 0.26 in both toluene and doped film. However, an organic light-emitting diode containing HAP-3MF achieved a high external quantum efficiency of 6.0%, indicating that HAP-3MF harvests singlet excitons through a thermally activated T1 → S1 pathway in the electroluminescent process.

Homopolymerization and Copolymerization of Isoprene and Styrene with a Neodymium Catalyst Using an Alkylmagnesium Cocatalyst

The catalyst system Nd(acac)3·2 H2O/Bu2Mg/CHCl3 shows a fairly high activity in both the homo- and copolymerization of isoprene (IP) and styrene (St) in toluene at 60°C. Copolymers obtained from various comonomer feed ratios were characterized by means of NMR spectroscopy and gel-permeation chromatography. The polyisoprene and poly(IP-co-St) obtained predominantly consist of cis-1,4 IP units. Monomer reactivity ratios were evaluated to be rIP = 5.4 and rSt = 0.38 in the copolymerization.

Copolymerization of butadiene and styrene with neodymium naphthenate based catalyst

Abstract Copolymerization of butadiene (Bd) and styrene (St) was carried out in toluene at 50 °C by a conventional rare earth catalytic system, Nd(naph)3–Al(i-Bu)3–Al(i-Bu)2Cl. It exhibited a high catalytic activity and high stereospecificity in the copolymerization. The influences of the conditions in polymerization on the yield, composition, microstructure and molecular weight of copolymer were thoroughly studied. According to the 13 C-NMR spectrum, the resultant copolymer containing 18% St units, and the diad fraction of St–trans Bd or St–vinyl Bd can hardly be found in its 13 C-NMR. The cis-1,4 content of Bd unit of the copolymer decreased little with the increase of St content. The GPC curves indicate the presence of two kinds of active sites in the polymerization.

One-pot synthesis of two new copper(I) coordination polymers: in situ formation of different ligands from 4-aminotriazole

Two Cu4I4 coordination polymers, [Cu2I2(aadtz)]n (1) and [Cu2I(dtz)]n (2) [aadtz = 4-[(1-aminoethylidene)-amino]-3,5-diethyl-1,2,4-triazole, dtz = 3,5-diethyl-1,2,4-triazole], were synthesized in a one-pot reaction of CuI and 4-amino-3,5-diethyl-1,2,4-triazole under solvothermal conditions. The organic components were generated in situ from a common triazolate source. The structures of the Cu4I4 units in the polymers are different. The Cu4I4cluster in complex 1 is an inorganic 8-membered ring with a chair–chair conformation, while the one in complex 2 is a distorted cubane. The topologies of the complexes were assigned as a two-dimensional 4-connected grid for 1 and a three-dimensional (3,4)-connected jph-type framework for 2. In addition, the luminescent properties of the complexes in the solid state were also investigated.

Solvothermal synthesis of two new coordination polymers: in situ heterocycle conversion and N-alkylation, network topologies and luminescence properties

Two new copper complexes [CuI4(L2)I5]n (1, L2 = 3,5-bis(1-ethylpyridinium-4-yl)-1,2,4-triazol-4-ide) and [CuI6(L3)3Br3]n (2, L3 = 3,5-bis(4-pyridyl)-1,2,4-triazolate) were obtained from the solvothermal reactions of different copper halides with 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (L1) in the presence of aqueous ammonia. The X-ray diffraction, IR spectrum and elemental analyses of 1 and 2 clearly show that the 1,3,4-oxadiazole ligand L1 has transformed into the triazolate ligands L2 and L3. Most fascinatingly, 1 represents the first example of an integrated reaction system involving heterocyclic conversion from oxadiazole to triazolate, N-alkylation, and further self-assembly of the in situ generated ligand L2 with metal cations to form a coordination polymer in one solvothermal spot. The possible formation mechanism of 1 is proposed, and in addition, the interesting topologies and luminescence properties of 2 are studied based on the results of the DFT calculations.

Copolymerization of Butadiene with Styrene by Nd(vers)3–Al(i‐Bu)3–CHCl3 Catalyst System

Abstract Copolymerization of butadiene (Bd) with styrene (St) was carried out by a catalytic system composed of Nd(versatate)3 (Nd(vers)3), Al(i‐Bu)3, and chloroform. The catalyst system exhibited a high catalytic activity and high stereospecificity of Bd in the copolymerization. The effects of Al/Nd molar ratio, Cl/Nd molar ratio, polymerization time, and monomer feed ratio on the copolymerization were thoroughly studied. It is found that the cis‐selectivity for Bd units of this catalyst was disturbed slightly by incorporating St unit in the copolymers, quite different from some other rare earth catalysts, and this is supposed to be related with monomer reactivity ratio of St (r St) in the copolymerization system.