Phenothiazine-Based Donor–Acceptor Polymers as Multifunctional Materials for Charge Storage and Solar Energy Conversion

The increasing energy demand for diverse applications requires new types of devices and materials. Multifunctional materials that can fulfill different roles are of high interest as they can allow fabricating devices that can both convert and store energy. Herein, organic donor–acceptor redox polymers that can function as charge storage materials in batteries and as donor materials in bulk heterojunction (BHJ) photovoltaic devices are investigated. Based on its reversible redox chemistry, phenothiazine is used as the main building block in the conjugated copolymer design and combined with diketopyrrolopyrrol and benzothiadiazole as electron-poor comonomers to shift the optical absorption into the visible region. The resulting polymers show excellent cycling stability as positive electrode materials in lithium–organic batteries at discharge potentials of 3.6–3.7 V versus Li/Li⁺ as well as good performances in BHJ solar cells with up to 1.9% power conversion efficiency. This study shows that the design of such multifunctional materials is possible, however, that it also faces challenges, as essential properties for good device function can lead to diametrically opposite requirements in materials design.     

Molecular Spring-like Triple-Helix Coordination Polymers as Dual-Stress and Thermally Responsive Crystalline Metal–Organic Materials

Elastic metal–organic materials (MOMs) capable of multiple stimuli-responsiveness based on dual-stress and thermally responsive triple-helix coordination polymers are presented. The strong metal-coordination linkage and the flexibility of organic linkers in these MOMs, rather than the 4 Å stacking interactions observed in organic crystals, causes the helical chain to act like a molecular spring and thus accounts for their macroscopic elasticity. The thermosalient effect of elastic MOMs is reported for the first time. Crystal structure analyses at different temperatures reveal that this thermoresponsiveness is achieved by adaptive regulation of the triple-helix chains by fine-tuning the opening angle of flexible V-shaped organic linkers and rotation of its lateral conjugated groups to resist possible expansion, thus demonstrating the vital role of adaptive reorganization of triple-helix metal–organic chains as a molecular spring-like motif in crystal jumping.     

Syntheses and Crystal Structures of Two Coordination Polymers with Aromatic Dioxide as Bridge Ligands

Two coordination polymers, namely, two-dimensional complex 1 {[Cu(μ- L)1.5(ClO4)2(H2O)].(H2O)0.5}n (L = pyrazine-1,4-dioxide) and one-dimensional complex 2 [Co(μ-L)Br2(H2O)2]n, have been synthesized with pyrazine-1,4-dioxide as bridging ligands, and their crystal structures were determined by X-ray crystallography. Crystal data for complex 1: monoclinic system, space group C2/c, with a = 23.310(3), b = 12.2338(17), c = 10.6075(15) , β = 110.487(2)°, V = 2833.6(7) 3, Z = 8, C6H9Cl2CuN3O12.5, Mr = 457.60, Dc = 2.145 g/cm3, F(000) = 1832 and μ = 1.998 mm-1; and those for 2: monoclinic system, space group C2/c, with a = 11.012(3), b = 7.483(2), c = 11.451(3) , β = 101.654(4)°, V = 924.2(4) 3, Z = 4, C4H8Br2CoN2O4, Mr = 366.87, Dc = 2.637 g/cm3, F(000) = 700 and μ = 10.487 mm-1. 1 shows a two-dimensional sheet structure on the ac plane through the coordination of μ-L bridging ligands with Cu(II) ions, while 2 displays a zigzag one-dimensional chain along the c axis via the coordination of μ-L bridging ligand with Co(II) ions. Hydrogen bonds in 1 and 2 make the sheets (or chains) connect each other to form a three-dimensional structure.     

Studies of Nano－sized Co304 as Anode Materials for Lithium－ion Batteries

The structural evolution of the Co₃O₄ fine powders prepared by rheological phase reaction and pyrolysis method upon different temperature has been investigated using X‐ray diffraction (XRD) topography. The electrochemical performance of Co₃O₄ electrode materials for Li‐ion batteries is studied in the form of Li/Co₃O₄ cells. The reversible capacity as high as 930 mAh/g for the Co₃O₄ sample heat‐treated at 600 °C is achieved and sustained over 30 times charge‐discharge cycles at room temperature. The detailed information concerning the reaction mechanism of Co₃O₄ active material together with lithium ion is obtained through ex‐situ XRD topography, X‐ray photoelectron spectroscopy (XPS) analysis and cyclic voltammetry (CV) technique. And it is revealed that a “two‐step” reaction is involved in the charge and discharge of the Li/Co₃O₄ cells, in which Co₃O₄ active material is reversibly reduced into xCoO(3 ‐ x)CoO and then into metallic Co.     

A ZINDO／1-CI Study of Substituted Triphenylamines for Use as Charge Transfer Materials

Electronic spectra of substituted triphenylamines are investigated in this paper by time dependent perturbation theory and ZINDO/1-CI calculation.     

Double Hydrothermal Synthesis of Graphene Supported TiO2（b） Nanosheets as Anode Materials for Lithium Ion Batteries

The synthesis of graphene supported TiO2（b） nanosheets by a double hydrother- mal method for lithium storage was reported. The titanate nanosheets synthesized by the first hydrothermal progress and the graphene oxide obtained by the oxidation of graphite were hydrothermally treated together to fabricate the TiO2（b）/graphene composite. The electrochemical measurements illustrate that the graphene supporter obviously improves the cyclic performance of TiO2（b）, which can be attributed to the better dispersion and the decrease of resistance for the TiO2（b） nanosheets in the composite.     

Syntheses and Crystal Structures of Two Two-dimensional Coordination Polymers with 2,3-Dimethylpyrazine-1,4-dioxide and Thiocyanate as Mixed Bridge Ligands

Two two-dimensional coordination polymers,[Cd(μ1,3-SCN-)2(μ1,6-L)]n 1 and [Co(μ1,3-SCN-)2(μ1,6-L)]n 2,have been synthesized with 2,3-dimethylpyrazine-1,4-dioxide (L) and thiocyanate as mixed bridging ligands,and their crystal structures were determined by X-ray crystallography.Both crystals belong to monoclinic system,space group C2/c.The other crystal parameters are as follows:for complex 1:a = 9.732(3),b = 14.658(5),c = 8.811(3) (A),β =102.935(4)°,Z = 4,V = 1225.1(7)(A)3,CsHsCdN4O2S2,Mr = 368.71,Dc.-- 1.999 g/cm3,F(000) =720 andμ = 2.117 mm-1;for complex 2:a = 9.528(7),b = 14.563(11),c = 8.415(6) (A),β =102.195(9)°,V= 1141.3(14) (A)3,Z = 4,C8H8CoN4O2S2,Mr = 315.23,Dc = 1.835 g/cm3,F(000) =636 andμ = 1.863 mm-1.The two complexes show similar two-dimensional sheet structures.Along the c axis one-dimensional chains are constructed by the coordination of Cd(Ⅱ) (or Co(Ⅱ))ions with μ1,6-L bridging ligand,and the μ1,3-SCN- bridging ligands make the chains connect to each other,resulting in the formation of a two-dimensional sheet on the ac plane.     

Acetic Anhydride as an Oxygen Donor in the Non-Hydrolytic Sol–Gel Synthesis of Mesoporous TiO2 with High Electrochemical Lithium Storage Performances

An original, halide-free non-hydrolytic sol–gel route to mesoporous anatase TiO₂ with hierarchical porosity and high specific surface area is reported. This route is based on the reaction at 200 °C of titanium(IV) isopropoxide with acetic anhydride, in the absence of a catalyst or solvent. NMR spectroscopic studies indicate that this method provides an efficient, truly non-hydrolytic and aprotic route to TiO₂. Formation of the oxide involves successive acetoxylation and condensation reactions, both with ester elimination. The resulting TiO₂ materials were nanocrystalline, even before calcination. Small (about 10 nm) anatase nanocrystals spontaneously aggregated to form mesoporous micron-sized particles with high specific surface area (240 m² g⁻¹ before calcination). Evaluation of the lithium storage performances shows a high reversible specific capacity, particularly for the non-calcined sample with the highest specific surface area favouring pseudo-capacitive storage: 253 mAh g⁻¹ at 0.1 C and 218 mAh g⁻¹ at 1 C (C=336 mA g⁻¹). This sample also shows good cyclability (92 % retention after 200 cycles at 336 mA g⁻¹) with a high coulombic efficiency (99.8 %). Synthesis in the presence of a solvent (toluene or squalane) offers the possibility to tune the morphology and texture of the TiO₂ nanomaterials.     

Use of Crown Ether Functions as Secondary Coordination Spheres for the Manipulation of Ligand–Metal Intramolecular Electron Transfer in Copper–Guanidine Complexes

Intramolecular electron transfer (IET) between a redox-active organic ligand and a metal in a complex is of fundamental interest and used in a variety of applications. In this work it is demonstrated that secondary coordination sphere motifs can be applied to trigger a radical change in the electronic structure of copper complexes with a redox-active guanidine ligand through ligand–metal IET. Hence, crown ether functions attached to the ligand allow the manipulation of the degree of IET between the guanidine ligand and the copper atom through metal encapsulation.     

Effects of Heavy Iodine Atoms and π-Expanded Conjugation on Charge Transfer Dynamics in Carboxylic Acid BODIPY Derivatives as Triplet Photosensitizers

Borondipyrromethene (BODIPY) chromophores are composed of a functional-COOH group at meso position with or without a biphenyl ring, and their compounds with heavy iodine atoms at −2, −6 positions of the BODIPY indacene core were synthesized. The photophysical properties of the compounds were studied with steady-state absorption and fluorescence measurements. It was observed that the absorption band is significantly red-shifted, and fluorescence signals are quenched in the presence of iodine atoms. In addition to that, it was indicated that the biphenyl ring does not affect the spectral shifting in the absorption as well as fluorescence spectra. In an attempt to investigate the effect of π-expanded biphenyl moieties and heavy iodine atoms on charge transfer dynamics, femtosecond transient absorption spectroscopy measurements were carried out in the environment of the tetrahydrofuran (THF) solution. Based on the performed ultrafast pump-probe spectroscopy, BODIPY compounds with iodine atoms lead to intersystem crossing (ISC) and ISC rates were determined as 150 ps and 180 ps for iodine BODIPY compounds with and without π-expanded biphenyl moieties, respectively. According to the theoretical results, the charge transfer in the investigated compounds mostly appears to be intrinsic local excitations, corresponding to high photoluminescence efficiency. These experimental findings are useful for the design and study of the fundamental photochemistry of organic triplet photosensitizers.     

Calcination-Free Synthesis of Well-Dispersed and Sub-10 nm Spinel Ferrite Nanoparticles as High-Performance Anode Materials for Lithium-Ion Batteries: A Case Study of CoFe2O4

Spinel ferrites are promising anode materials for lithium-ion batteries (LIBs) owing to their high theoretical specific capacities. However, their practical application is impeded by inherent low conductivity and severe volume expansion, which can be surpassed by increasing the surface-to-volume ratio of nanoparticles. Currently, most methods produce spinel ferrite nanoparticles with large size and severe aggregation, degrading their electrochemical performance. In this study, a low-temperature aminolytic route was designed to synthesize sub-10 nm CoFe₂O₄ nanoparticles with good dispersion through carefully exploiting the reaction of acetates and oleylamine. The performance of CoFe₂O₄ nanoparticles obtained by a traditional co-precipitation method was also investigated for comparison. This work demonstrates that CoFe₂O₄ nanoparticles synthesized by the aminolytic route are promising as anode materials for LIBs. Besides, this method can be extended to design other spinel ferrites for energy storage devices with superior performance by simply changing the starting material, such as MnFe₂O₄, MgFe₂O₄, ZnFe₂O₄, and so on.     

Selected-Control Synthesis of Monodisperse Fe3O4@C Core–Shell Spheres,Chains, and Rings as High-Performance Anode Materials for Lithium-Ion Batteries

A method is reported for the first time for the selected-control, large-scale synthesis of monodispersed Fe₃O₄@C core–shell spheres, chains, and rings with tunable magnetic properties based on structural evolution from eccentric Fe₂O₃@poly(acrylic acid) core–shell nanoparticles. The Fe₃O₄@C core–shell spheres, chains, and rings were investigated as anode materials for lithium-ion batteries. Furthermore, a possible formation mechanism of Fe₃O₄@C core–shell chains and rings has also been proposed.     

Rational Construction of 2D Fe3O4@Carbon Core–Shell Nanosheets as Advanced Anode Materials for High-Performance Lithium-Ion Half/Full Cells

Transition metal oxides have vastly limited practical application as electrode materials for lithium-ion batteries (LIBs) due to their rapid capacity decay. Here, a versatile strategy to mitigate the volume expansion and low conductivity of Fe₃O₄ by coating a thin carbon layer on the surface of Fe₃O₄ nanosheets (NSs) was employed. Owing to the 2D core–shell structure, the Fe₃O₄@C NSs exhibit significantly improved rate performance and cycle capability compared with bare Fe₃O₄ NSs. After 200 cycles, the discharge capacity at 0.5 A g⁻¹ was 963 mA h g⁻¹ (93 % retained). Moreover, the reaction mechanism of lithium storage was studied in detail by ex situ XRD and HRTEM. When coupled with a commercial LiFePO₄ cathode, the resulting full cell retains a capacity of 133 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹, which demonstrates its superior energy storage performance. This work provides guidance for constructing 2D metal oxide/carbon composites with high performance and low cost for the field of energy storage.     

Broadly Applicable Synthesis of Arylated Dithieno[3,2-b:2′,3′-d]pyrroles as Building Blocks for Organic Electronic Materials

A novel and versatile method for the N-arylation of dithieno[3,2-b:2′,3′-d]pyrrole (DTP) is presented. By Pd- or Cu-catalyzed coupling a variety of arenes and acenes were directly attached at the DTP−nitrogen yielding a variety of functionalized DTPs. Investigations on optical and redox properties led to valuable structure-property relationships, which were corroborated by quantum chemical calculations. Further functionalization and elongation of the conjugation of an acceptor-substituted DTP was elaborated to result in complex cruciform-type donor−acceptor oligomers, which were investigated and implemented in single material organic solar cells.     

Syntheses,Crystal Structures and Fluorescence of Cadmium(II) Coordination Polymers with Pyrazine-1,4-dioxide, 2-Methylpyrazine-1,4-dioxide and Thiocyanate as Mixed Bridge Ligands

1 INTRODUCTION For a long time much research interest has been focused on the coordination polymeric compounds because such new coordination polymers may afford new materials with useful properties, such as catalytic activity, micro-porosity, electrical conduc- tivity, non-linear optical activity, magnetic coupling behavior and so on[1, 2]. Thiocyanate anion as well as pyrazine-1,4-dioxide and its derivatives belongs to very useful bridge ligands and many complexes[3, 4] with one of them e…