Organic Backbone Research Articles

A novel 3D pillar-layered metal-organic framework: Pore-size-dependent catalytic activity and CO2/N2 affinity

The structure–activity relationship plays the main role in the applicability of Metal-organic Frameworks (MOFs) in different areas including catalysis. Regarding to this herein a novel pillar-layered MOF (TMU-52) that is isostructural to our recently reported TMU-25 is introduced. The structure of this framework was analyzed using X-ray crystallography, FT-IR spectroscopy, Thermogravimetric and elemental analyses. According to the similar organic and inorganic backbone, a comparative study was done on catalytic manner of TMU-25 and TMU-52 toward in aldol-type condensation reaction. TMU-52 was designed through replacing the biphenyl core in the pillar linker of TMU-25 with phenyl group as a better candidate heterogeneous catalysis. The selectivity of the TMU-52 was higher owing to its narrower channels. CO2/N2 affinity of these structures was also investigated.

Modification of covalent organic frameworks with dual functions ionic liquids for membrane-based biogas upgrading

Development of high-performance membranes for biogas upgrading is an urgent demand for the application of membrane technology in the field of renewable energy. Covalent organic frameworks (COFs) exhibit promising potential in membrane-based separation for their highly ordered crystalline porous structure, total organic backbone and tailored functionality. However, the limited functional groups on frameworks and relatively larger pore size of existing COFs restrict further improvement in the separation efficiency especially for gas mixtures. This work reports a novel strategy for modifying the pore of COF-300 with imidazolium-based ionic liquid [bmim][Tf2N] by post-impregnation and then incorporate the composite particles IL@COF-300 into Pebax matrix to prepare mixed matrix membranes (MMMs). The IL decreases the pore size of COF-300 from 1.28 nm to 1.09 nm and increases the diffusion coefficient difference (DCO2/DCH4) between CO2 and CH4. Moreover, the presence of IL with high CO2 solubility endows the COF-300 pores with CO2-facilitating ability and thus increasing the solubility difference (SCO2/SCH4). The dual functions of IL lead to an enhanced separation performance of the resultant IL@COF-300/Pebax MMMs with an optimal permeability of 1601 Barrer and a CO2/CH4 gas selectivity of ~39, i.e. 209% and 87% higher than the pristine Pebax membrane, respectively, breaking the trade-off between permeability and selectivity and surpassing the Robeson 2008 upper-bound. The membrane also exhibits superior long-term operation stability during two months.

Crystal Orientation Drives the Interface Physics at Two/Three-Dimensional Hybrid Perovskites.

Combining halide perovskites with tailored dimensionality into two/three-dimensional (2D/3D) systems has revealed a powerful strategy to boost the performances of perovskite photovoltaics (PVs). Despite recent advances, a clear understanding of the intimate link between interface structure and physics is still missing, leading so far to a blind optimization of the 2D/3D PVs. Here, we reveal the impact of 2D/3D crystal alignment in driving interface charge-recombination dynamics. The 2D crystal growth and orientation are manipulated by specific fluorination of phenethylammonium (PEA), used here as the organic cation backbone of the 2D component. By means of time-resolved optoelectronic analysis from the femto- to microsecond regions, we demonstrate a static function of the 2D layer as an electron barrier and homogeneous surface passivant, together with a dynamic role in retarding back charge recombination. Our results reveal a crucial dependence of such beneficial effects with the 2D layer, leading to an enhanced open-circuit voltage (Voc), mostly attributed to the 2D phase which orients parallel on the 3D layer. Such findings provide a deep understanding and delineate precise guidelines for the smart design of multidimensional perovskite interfaces for advanced PVs and beyond.

(Invited) Searching for High Potential Organic Cathode Materials for High Energy Green and Sustainable Batteries

Thanks to the use of abundant chemical elements, organic chemistry provides great opportunities for discovering innovative electrode materials, which could be prepared (i) from renewable resources (biomass) and (ii) via eco-efficient processes, making the concept of greener and sustainable batteries possible [1]. We are putting a lot of efforts on greener and sustainable organic non-aqueous and aqueous batteries at the IMN. In this communication, we report on novel crystallized organic positive electrode materials for the non-aqueous application of organic batteries. However the synthesis of high-voltage lithiated materials is rather challenging, so very few examples of all-organic Li-ion cells currently exist. Compounds of the Mn+ 2/n-p-DHT (with Mn+ = Li+, Mg2+, Ca2+ and Ba2+) family were studied to better understand the effect of substitution chemistry on the redox properties of the Li-diphenolate cycle of p-DHT. This innovative chemical approach makes it possible to tune the redox potential of lithiated organic electrode materials, by playing on the nature and the ionic potential of a spectator cation in the host structure. Indeed, by adjusting the attractor/donor electron effects in the organic redox-active backbone, it is possible to modify the redox potential of the molecule by inductive effect. We show that substituting magnesium (2,5-dilithium-oxy)-terephthalate for lithium (2,5-dilithium-oxy)-terephthalate enables an outstanding voltage gain of 800 mV, leading to a high operating voltage of 3.4V vs. Li+/Li [2]. This Mg(Li2)-p-DHT compound is the first lithiated organic positive electrode material with an operating potential as high as that of LiFePO4. Based on this finding, full organic Li-ion cells with an output voltage of 2.5V and long cycle life have been achieved, thus making a big step forward the design of high energy green and sustainable organic batteries.

Benzannulated N-heterocyclic plumbylene: An efficient catalyst in ring opening polymerization of l-lactide

Main-group metal-based catalysts have attracted considerable attentions due to their complementary reactivities to transition metals. In searching for the catalytic application of heavy divalent Group 14 derivatives, we came to discover that the benzannulated N-heterocyclic plumbylene (1) could serve as an effective catalyst for ring-opening polymerization of l-lactide (L-LA) at room temperature. In the presence of benzyl alcohol (BnOH), 97% conversion of L-LA was accomplished in 10 min under a catalyst loading of merely 0.3 mol% ([LA]:[1]:[BnOH] = 400:1.2:1.2, [1] = 1.2 mM). Compared to the polymeric plumbylene ([Pb(μ-OiPr)2]∞), the excellent catalytic activity of 1 at ambient temperature may be ascribed to the steric and electronic stabilizations of the Pb2+ center by the organic backbone. Thus, thermal activation is no longer required to expose the Lewis acidic metal center for polymerization.

Guest-Assisted Proton Conduction in the Sulfonic Mesoporous MIL-101 MOF.

Post-synthesis modification of MIL-101(Cr)-NO2 was explored in order to decorate the organic backbone by propyl-sulfonic groups, with the aim to incorporate mobile and acidic protons for solid-state proton electrolyte applications. The resulting solid switched from insulating towards proton superconductive behavior under humidity, while the conductivity recorded at 363 K and 95 % relative humidity reached 4.8×10-3 S cm-1 . Propitiously, the impregnation of the material by strong acidic molecules (H2 SO4 ) further boosted the proton conductivity performances up to the remarkable σ value of 1.3×10-1 S cm-1 at 363 K/95 % RH, which reaches the performances of the best proton conductive MOF reported so far.

Amphiphilic semiconducting oligomer for single NIR laser induced photothermal/photodynamic combination therapy

Developing single wavelength laser triggered organic nanoplatforms for combined photothermal therapy (PTT)/photodynamic therapy (PDT) is a great prospect for biomedicine. However, most of organic nanoparticles were prepared by nanoprecipitation method, which have the potential issues of nanoparticles dissociation. In this work, a novel amphiphilic semiconducting oligomer DPP-BT-PEG which composed of a hydrophobic organic backbone and hydrophilic PEG side chains was designed and prepared. Due to the amphiphilic characteristic of DPP-BT-PEG, ideal nanoagents DPP-BT-PEG NPs were self-assembled by dissolving the amphiphilic molecule in water, which exhibited outstanding water-solubility, good biocompatibility, superb photostability, and excellent structural stability. Notably, upon exposure to a single near-infrared (NIR) laser, these nanoagents can produce cytotoxic hyperthermia and ROS simultaneously for effective cancer treatment due to the combined effects of PTT and PDT. This study supplies a promising tactic to construct non-dissociated NIR-absorbing organic nanoplatforms for combination cancer therapy, opening new dimension for biomedicine.

Synthesis of Functionalized Azobiphenyl- and Azoterphenyl- Ditopic Linkers: Modular Building Blocks for Photoresponsive Smart Materials.

Modular synthesis of structurally diverse functionalized azobiphenyls and azoterphenyls for the realization of optically switchable materials has been described. The corresponding synthesis of azobiphenyls and azoterphenyls by stepwise Mills/Suzuki-Miyaura cross-coupling reaction, proceeds with high yields and provides facile access to a library of functionalized building blocks. The synthetic methods described herein allow combining several distinct functional groups within a single unit, each intended for a specific task, such as 1) the -N=N- azobenzene core as a photoswitchable moiety, 2) aryls and heteroaryls, functionalized with carboxylic acids or pyridine at its peripheries, as coordinating moieties and 3) varying substitution, size and length of the backbone for adaptability to specific applications. These specifically designed azobiphenyls and azoterphenyls provide modular bricks, potentially useful for the assembly of a variety of polymers, molecular containers and coordination networks, offering a high degree of molecular functionality. Once integrated into materials, the azobenzene system, as a side group on the organic linker backbone, can be exploited for remotely controlling the structural, mechanical or physical properties, thus being applicable for a broad variety of 'smart' applications.

Aliphatic Long-Chain Polypyrophosphates as Biodegradable Polyethylene Mimics.

Biodegradable polyethylene mimics have been synthesized by the introduction of pyrophosphate groups into the polymer backbone, allowing not only hydrolysis of the backbone but also further degradation by microorganisms. Because of cost, low weight, and good mechanical properties, the use of polyolefins has increased significantly in the past decades and has created many challenges in terms of disposal and their environmental impact. The durability and resistance to degradation make polyethylene difficult or impossible for nature to assimilate, thus making the degradability of polyolefins an essential topic of research. The biodegradable polypyrophosphate was prepared via acyclic diene metathesis polymerization of a diene monomer. The monomer is accessible via a three-step synthesis, in which the pyrophosphate was formed in the last step by DCC coupling of two phosphoric acid derivatives. This is the first report of a pyrophosphate group localized in an organic polymer backbone. The polypyrophosphate was characterized in detail by NMR spectroscopy, size exclusion chromatography, FTIR spectroscopy, differential scanning calorimetry, and thermogravimetry. X-ray diffraction was used to compare the crystallization structure in comparison to analogous polyphosphates showing poly(ethylene)-like structures. In spite of their hydrophobicity and water insolubility, the pyrophosphate groups exhibited fast hydrolysis, resulting in polymer degradation when films were immersed in water. Additionally, the hydrolyzed fragments were further biodegraded by microorganisms, rendering these PE mimics potential candidates for fast release of hydrophobic cargo, for example, in drug delivery applications.

Recent advances in covalent organic frameworks (COFs) as a smart sensing material.

As a newly emerging kind of porous material, covalent organic frameworks (COFs) have drawn much attention because of their fascinating structural features (e.g., divinable structure, adjustable porosity and total organic backbone). Since the seminal work of Yaghi and co-workers reported in 2005, the COF materials have shown superior potential in diverse applications, such as gas storage, adsorption, optoelectronics, catalysis, etc. Recently, COF materials have shown a new trend in sensing fields. This critical review briefly describes the synthesis routes for COF powders and thin films. What's more, the most fascinating and significant applications of COFs in sensing fields including explosive sensing, humidity sensing, pH detection, biosensing, gas sensing, metal ion sensing, and other substance sensing are summarized and highlighted. Finally, the major challenges and future trends of COFs with respect to their preparation and sensing applications are discussed.

Enhancing the X-ray contrast of polymeric biochromatography particles for three-dimensional imaging

A major limitation of the three-dimensional imaging of polymeric biochromatography particle packings using X-ray computed tomography is that the particles have a low density and a high porosity, making them almost undistinguishable from the surrounding liquid phase. Additionally, the employed media are typically composed of materials with low atomic numbers, which exhibit low X-ray absorption. We report an improvement of packed column reconstruction using micro X-ray computed tomography. A simple, inexpensive, and fast method to increase the contrast factor of highly porous polymer-based chromatographic particles was developed by applying a modified pore-blocking method. This approach relies on the selective filling of the porous chromatographic particles with a hydrophilic phase while a hydrophobic phase occupies the void spaces between the particles. The hydrophilic phase contains a dissolved X-ray absorbing radiocontrast agent. No chemical modifications of the chromatographic beads or columns were necessary. The developed method can be applied in-situ in a previously packed column and can be used for media with different organic backbones. We show the applicability of this method by carrying out the first 3D-reconstruction of packed micro columns with an inner diameter of 760 μm. The micro column contained agarose- and methacrylate-based particles commonly used in preparative biochromatography with mean diameters of 40 and 65 μm, respectively. Based on the obtained high-resolution 3D-reconstructions, we exemplarily computed packing properties such as global extraparticle porosity and radial porosity profiles, and visualized the presence of void spaces using 3D image analysis.

Electrocatalytic CO₂ Reduction: From Homogeneous Catalysts to Heterogeneous-Based Reticular Chemistry.

CO2, emitted mainly from fossil fuel combustion, is one of the major greenhouse gases. CO2 could be converted into more valuable chemical feedstocks including CO, HCOOH, HCHO, CH3OH, or CH4. To reduce CO2, catalysts were designed and their unique characteristics were utilized based on types of reaction processes, including catalytic hydrogenation, complex metal hydrides, photocatalysis, biological reduction, and electrochemical reduction. Indeed, the electroreduction method has received much consideration lately due to the simple operation, as well as environmentally friendly procedures that need to be optimized by both of the catalysts and the electrochemical process. In the past few decades, we have witnessed an explosion in development in materials science—especially in regards to the porous crystalline materials based on the strong covalent bond of the organic linkers containing light elements (Covalent organic frameworks, COFs), as well as the hybrid materials that possess organic backbones and inorganic metal-oxo clusters (Metal-organic frameworks, MOFs). Owing to the large surface area and high active site density that belong to these tailorable structures, MOFs and COFs can be applied to many practical applications, such as gas storage and separation, drug release, sensing, and catalysis. Beyond those applications, which have been abundantly studied since the 1990s, CO2 reduction catalyzed by reticular and extended structures of MOFs or COFs has been more recently turned to the next step of state-of-the-art application. In this perspective, we highlight the achievement of homogeneous catalysts used for CO2 electrochemical conversion and contrast it with the advances in new porous catalyst-based reticular chemistry. We then discuss the role of new catalytic systems designed in light of reticular chemistry in the heterogeneous-catalyzed reduction of CO2.

Four 3D Mn(II) coordination polymers with diverse carboxylate-bridged magnetic chains: Syntheses, crystal structures, magnetic properties

Four new three-dimensional Mn(II) coordination polymers with two isomeric ligands, 5-(3-nitro-4-carboxylphenyl)isophthalic acid (H3L1) and 5-(2-nitro-4-carboxylphenyl)isophthalic acid (H3L2), have been prepared and structurally and magnetically characterized. They are of the formula [Mn(HL1)(CH3CN)] (1), [Mn(L2)]·H2O·H3O (2), [Mn3(L2)2(DMF)2]·H2O (3), [Mn4(HL2)4(H2O)5]·2H2O (4). Compounds 1–3 contain diverse alternating magnetic chain’s sequences in which the chains are linked by the organic spacers into 3D structures. In 1, the two double [(μ-Ocarboxylate)2 and (μ-syn-anti-COO)2] bridges with apparently different structural parameters alternate in the − ABAB − sequence. While in 2, the two sets of double μ-syn-anti-carboxylate bridges with slightly different structural parameters also alternate in the -ABAB- sequence. In 3, the double (μ-syn-anti-COO)2 bridges and (μ-ODMF)(μ-syn-anti-COO)(μ3-COO) triple bridges alternate in the -ABB- sequence. Compound 4 contains two sets of independent motifs: one is 1D chain based on three different double (μ-syn-anti-COO)2 bridges alternate in the -ABC- sequences; the other is 1D tape-like motifs with three different single μ-syn-anti-COO bridges. Two sets of motifs in 4 are alternately linked together by the organic backbones into a complicated 3D structure. Compounds 1, 2 and 4 exhibit weak antiferromagnetic couplings. A magnetostructural survey indicates that the antiferromagnetic coupling through the (μ-syn-anti-COO)2 bridges decreases as the Mn⋯Mn distances increases and the magnitude of antiferromagnetic coupling mainly depends on the MnOMn angle for the double (μ2-Ocarboxylate)2 bridges.

Facile Synthesis, Crystal Structure, DFT Calculation and Biological Activities of 4-(2-fluorophenyl)-3-(3-methoxybenzyl)-1H-1,2,4-triazol-5 (4H)-one (5).

In the past few decades, design, synthesis, and characterization of novel heterocyclic compounds with auspicious biological profile received the considerable attention of the scientific community. Among them, the small and simple organic molecular backbone like triazole moiety have a broad spectrum of applications in the medicinal as well as diagnostic areas. The objective of present study was synthesis, characterization, and exploration of biological profile of 4-(2-fluorophenyl)-3-(3-methoxybenzyl)-1H-1,2,4-triazole-5(4H)-one (5). The tautomeric interconversion of the molecule was observed by the single crystal XRD and DFT analysis. N-(2-fluorophenyl)-2-[2-(3-methoxyphenyl)acetyl]hydrazine carboxamide (4) was synthesized by the condensation of 2-(3-methoxyphenyl)acetohydrazide (3) with 1-fluoro-2- isocyanatobenzene. The dehydrocyclization of compound (4) yielded target compound (5) by refluxing in 2 N aqueous sodium hydroxide solutions. The target molecule was characterized by FTIR, 1H NMR, 13C NMR, single crystal X-ray diffraction analysis and DFT calculation. The enzymatic assay measurements were carried out by using a microplate reader (OPTI Max, Tunable Microplate Reader; Wavelength range: 340-850 nm; for 96-well plates) while DFT calculation was performed by Gaussian 09 package. The XRD result and DFT calculations showed that molecule 5 predominantly exists in thione conformation and crystallized in the triclinic system of P-1 space group. Furthermore, for the practical applicability of synthesized compound 5, the in vitro acetylcholinesterase as well as α-glucosidase inhibition activities were performed and found moderate enzyme inhibition potential comparable with that of reference inhibitors. This study might be helpful for future design and development of potent enzyme inhibitor to control Alzheimer's as well as diabetic disease. The DFT and single crystal XRD analysis data might be helpful for understanding the mechanism of drug binding and its mode of action.

Solution and Solid State Structural Chemistry of Th(IV) and U(IV) 4-Hydroxybenzoates.

Organic ligands with carboxylate functionalities have been shown to affect the solubility, speciation, and overall chemical behavior of tetravalent metal ions. While many reports have focused on actinide complexation by relatively simple monocarboxylates such as amino acids, in this work we examined Th(IV) and U(IV) complexation by 4-hydroxybenzoic acid in water with the aim of understanding the impact that the organic backbone has on the solution and solid state structural chemistry of thorium(IV) and uranium(IV) complexes. Two compounds of the general formula [An6O4(OH)4(H2O)6(4-HB)12]· nH2O [An = Th (Th-1) and U (U-1); 4-HB = 4-hydroxybenzoate] were synthesized via room-temperature reactions of AnCl4 and 4-hydroxybenzoic acid in water. Solid state structures were determined by single-crystal X-ray diffraction, and the compounds were further characterized by Raman, infrared, and optical spectroscopies and thermogravimetry. The magnetism of U-1 was also examined. The structures of the Th and U compounds are isomorphous and are built from ligand-decorated oxo/hydroxo-bridged hexanuclear units. The relationship between the building units observed in the solid state structure of U-1 and those that exist in solution prior to crystallization as well as upon dissolution of U-1 in nonaqueous solvents was investigated using small-angle X-ray scattering, ultraviolet-visible optical spectroscopy, and dynamic light scattering. The evolution of U solution speciation as a function of reaction time and temperature was examined. Such effects as well as the impact of the ligand on the formation and evolution of hexanuclear U(IV) clusters to UO2 nanoparticles compared to prior reported monocarboxylate ligand systems are discussed. Unlike prior reported syntheses of Th and U(IV) hexamers where the pH was adjusted to ∼2 and 3, respectively, to drive hydrolysis, hexamer formation with the HB ligand appears to be promoted only by the ligand.

Charge Transport through Single Molecules Connected to Semiconductor Electrodes

Single molecule electrical measurements have revolutionised our understanding of how charge flows through individual molecules and biomolecules in a wide variety of environments and are important for applications ranging from energy technology, DNA sequencing and interfacial electrochemistry. Such measurements have been typically made with metallic contacts but lately we have managed to extend this to the semiconductor gallium arsenide. This advance is important since future applications of molecular electronics will rely on integrating molecules alongside conventional semiconductor electronic technologies. In a recent publication in Nano Letters [1] we have shown that it is possible to make measurements of single molecules connected at one end to gallium arsenide and at the other end to a gold scanning tunnelling microscope tip. Using this methodology we can record current-voltage response of semiconductor – molecule – metal devices and measure the electrical conductance of single molecules in such junctions. For these measurements of charge transfer at the at the semiconductor-molecule interface the gallium arsenide surfaces are modified with organic self-assembled monolayers. Semiconductor / molecule(s) / metal junctions are formed by bringing a gold STM tip into contact with the molecular monolayer. Such junctions behave as a Schottky diode with the rectification ratio of the fabricated device being dependent on both the nature of the organic backbone and the electronic properties of the semiconductor. As well as recording I-V characteristics with the STM tip contacting the molecular monolayer, by using a time-dependent STM technique we were also able to detect the contribution of a single molecule to charge transport across the molecular junction. As well as showing that it is possible to form single molecule devices contacted to the semiconductor gallium arsenide we have also recently demonstrated that such single molecule devices show a strong photocurrent response.[2] Gallium arsenide is able to efficiently absorb visible light as it is a III-V direct bandgap (1.42 eV at room temperature) semiconductor and illumination of the molecular junction led to large changes in the current-voltage response. The junction configuration is schematically illustrated in the figure from reference [2] which shows a molecule bridging between the GaAs surface and the gold STM tip. The hemispheres in the GaAs substrate in this illustration depict the space charge layer (SCL) from which the charge carriers are collected. The resulting photo-generated charge carriers are transported to the metal electrode (STM tip) through the bridging organic dithiol giving the photo-current. Importantly, the photo-current response in these hybrid junctions can be controlled through the choice of molecular bridge as well as the doping density of the semiconductor amd the light intensity and wavelength.[2] In the dark high current rectification (> 103) is achieved with low-doping GaAs and saturated alkyl bridges and appreciable photocurrent is achieved upon illumination of these junctions. The response of the device is greatly influenced by molecular orbital alignment and this can be controlled by switching from saturated molecular bridges to conjugated ones with lower HOMO-LUMO gaps. Good photodiode functionality can be achieved with a space charge layer of only a few nanometres. Since the response of the molecular junctions is controlled by the combined properties of the semiconductor and the molecular wire this significantly extend of the single-molecule electronics “tool-box” as well as providing new methodologies for studying charge transfer at semiconductor-molecule interfaces. The presentation concludes with discussion of the perspective of single molecule photo-electrochemistry.

From properties to materials: An efficient and simple approach.

We present an inverse-design method, the poor man's materials optimization, that is designed to identify materials within a very large class with optimized values for a pre-chosen property. The method combines an efficient genetic-algorithm-based optimization, an automatic approach for generating modified molecules, a simple approach for calculating the property of interest, and a mathematical formulation of the quantity whose value shall be optimized. In order to illustrate the performance of our approach, we study the properties of organic molecules related to those used in dye-sensitized solar cells, whereby we, for the sake of proof of principle, consider benzene as a simple test system. Using a genetic algorithm, the substituents attached to the organic backbone are varied and the best performing molecules are identified. We consider several properties to describe the performance of organic molecules, including the HOMO-LUMO gap, the sunlight absorption, the spatial distance of the orbitals, and the reorganisation energy. The results show that our method is able to identify a large number of good candidate structures within a short time. In some cases, chemical/physical intuition can be used to rationalize the substitution pattern of the best structures, although this is not always possible. The present investigations provide a solid foundation for dealing with more complex and technically relevant systems such as porphyrins. Furthermore, our "properties first, materials second" approach is not limited to solar-energy harvesting but can be applied to many other fields, as briefly is discussed in the paper.

Synthesis, spectroscopic and electrochemical characterization of Co(II)-terpyridine based metallopolymer

A new oligothienyl-based metallopolymer including Co(terpyridine)2 complex units is synthesised by electrochemical oxidation of the relevant monomer. The chemical structure of the polymer chains and the electronic interaction between the organic portions and the metal centres are investigated by spectroscopic (X-rays photoelectron spectroscopy included), electrochemical, and spectroelectrochemical techniques. Thanks to the low potential of the Co(III)/Co(II) redox couple in the Co(terpyridine)2 complex and to the presence of oligothienyl spacer, strong electron interaction between the organic backbone and the metal centres have been demonstrated.

Study of Six Green Insensitive High Energetic Coordination Polymers Based on Alkali/Alkali-Earth Metals and 4,5-Bis(tetrazol-5-yl)-2 H-1,2,3-triazole.

Constructing insensitive high-performance energetic coordination polymers (ECPs) with alkali/alkali-earth metal ions and a nitrogen-rich organic backbone has been proved to be a feasible strategy in this work. Six diverse dimensional novel ECPs (compounds 1-6) were successfully synthesized from NaI , CsI , CaII , SrII , BaII ions and a nitrogen-rich triheterocyclic 4,5-bis(tetrazol-5-yl)-2 H-1,2,3-triazole (H3 BTT). All compounds show outstanding stability and low sensitivity, the thermal stability of these ECPs are significantly improved as the structural reinforcement increases from 1D to 3D, in which the decomposition temperature of 3D BaII based compound 6 is as high as 397 °C. Long-term storage experiments show that compounds 5 and 6 are stable enough at high temperature. Moreover, the six compounds hold considerable detonation performances, in which CaII based compound 5 possesses the detonation velocity of 9.12 km s-1 , along with the detonation pressure of 34.51 GPa, exceeding those of most energetic coordination polymers. Burn tests further certify that the six compounds can be versatile pyrotechnics.

Sexithiophene-Based Photovoltaic Cells with High Light Absorption Coefficient via Crystalline Polymorph Control

Herein, we report an efficient approach to control the crystalline polymorph of evaporated α-sexithiophene (6T) thin films by keeping them overnight (12 h) under vacuum. Further, we investigated the effects on the performance of organic photovoltaic devices of controlling the 6T polymorph via this vacuum technique so that the films take on the low-temperature (LT) polymorph (in which the backbones of the 6T molecules lie flatter on the substrate—the so-called “lying-down” orientation). Our results revealed that when the organic layer was deposited directly onto a copper(I) iodide interlayer, the angle between the organic backbone and the substrate was reduced in the LT polymorph compared with the high-temperature (HT) polymorph. The power conversion efficiency of solar cells could thus be enhanced from 0.58 to 1.77% via a change in the crystal polymorph of the 6T layer from HT to LT by simply keeping the films in vacuum for 12 h.