Fingerprints of π-conjugated compounds are ubiquitous in nature and play a crucial part in human existence. For instance, cis-retinal, an endogenous π-conjugated molecule present in the eye, performs a vital role in the function of visual perception. π-Conjugated molecules have also received a great deal of attention owing to their intriguing optical properties and created a surge in optoelectronics. Varieties of π-conjugated molecules/oligomers have been developed and explored for a number of applications such as organic lightemitting diodes (OLEDs), organic field-effect transistors (OFETs), organic photovoltaics (OPVs), and sensors, among others. While the extended πdelocalization in one-dimensional (1D) polymers versus oligomers produce superior optical and electronic properties, further extension of π-delocalization to the second dimension (2D) is expected to give rise even more intriguing properties as revealed by theoretical studies. As a matter of fact, graphene is the best example of 2D-conjugated polymers, but its zero-band-gap behavior is a major impediment for semiconducting applications. In contrast, it was challenging to prepare 2D crystalline polymers until the discovery of boroxine/boronate ester linked covalent organic frameworks (COFs) by Yaghi and co-workers. COFs are a new class of porous crystalline polymers in which organic building blocks are held together by covalent bonds. These polymers exhibit potential applications in gas storage, energy storage, photocatalyst, heterogeneous catalysis, sensors, etc. However, the first π-conjugated COF was realized in 2009 via the introduction of imine linker (−CN−) between the building blocks. Since then, wide varieties of COFs with various πdelocalization promoting spacers have been developed and explored their electronic and optical properties and pertinent applications. In this review, we will highlight the importance of 2D π-conjugated COFs and their achievements in developing novel functionalities.

This work aimed to investigate the effect of two types of phosphorus-containing flame retardants (P-FRs) with different chemical surroundings (phenylphosphonate-based (PO-Ph) and phenylphosphoric-based (PO-OPh)) on the flameretardant efficiency for diglycidyl ester of bisphenol-A type epoxy (EP) resin. The two series of P-FRs which were named as FPx and FPOx (x=1, 2 and 3), respectively, showed reactivity with epoxy group that was examined by differential scanning calorimetric (DSC) and variable temperatures FTIR spectrum (VT-FTIR). A comparative study between the FPx and FPOx (x=1, 2 and 3) contaning flame-retardamt epoxy was carried out via investigating their flammability, thermal stability and mechanical properties. The most significant difference on flame retardancy between them was that FPx (x=1, 2 and 3) endowed EP with V-0 rating in UL 94 test at 5 wt% loading, while FPOx (x=1, 2 and 3) showed no rating at such loading. Importantly, it is found that there was almost 10 times difference in the flame-retardant efficiency for epoxy resin between FPx and FPOx, though they had similar chemically molecular structures. Moreover, TGA-FTIR and TGA-MS coupling techniques (TGA, thermalgravimetric analysis; MS, mass spectroscopy) were employed to study the thermal decomposition of FP1 and FPO1; the impacts of FP1 and FPO1 on the thermal decomposition of EP were studied by TGA-FTIR as well. Furthermore, an online temperature detection experiment was designed to collect the temperatures by thermocouple and infrared thermometers, respectively in the UL 94 test. Based on the above results, the flame-retardant mechanisms of FP1 and FPO1 in EP were discussed. In addition, the impact of P-FRs on mechanical properties of EP was studied by means of tensile test and dynamic mechanical analysis .

No abstract

The syntheses of Zn(II), Cd(II) and Cu(II) complexes of 2,5-bis{N-(2,6-diisopropylphenyl)iminomethyl}pyrrole (DIP(2)pyr)H 1 and their catalytic activities in CO(2) fixation are reported. The structures of these complexes were characterized by IR, (1)H, (13)C NMR and single crystal X-ray diffraction techniques. The catalytic activities of these complexes for the cycloaddition of CO(2) to an epoxide under one atmosphere of pressure and mild temperature conditions to yield cyclic carbonate have been studied. Among the four complexes synthesized, the Zn(II) and Cu(II) complexes were found to be versatile whereas the Cu(II) complex was more selective in the conversion. They were highly effective for the conversion of monosubstituted terminal epoxides, disubstituted terminal and internal epoxides to their corresponding cyclic carbonates with good to high yields.

Fluorescent porous organic polymers are a unique class of materials owing to their strong aggregation induced emission, long range exciton migration and permanent porosity, thus envisioned to possess a wide range of applications (sensing, OLEDs).

Cu-doped graphene (graphenit-Cu) was successfully prepared through chemical reduction method, and its surface morphology, crystalline structure and Cu content in graphenit-Cu were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductive couple plasma (ICP) and electrochemical cyclic voltammetry, respectively. Graphenit-ox/epoxy systems and graphenit-Cu/epoxy systems were prepared, and the contents of graphenit-ox and graphenit-Cu were kept as 1 and 3 wt%, respectively. The effect of graphenit-ox or graphenit-Cu on the flame retardancy, combustion properties, thermal degradation and thermomechanical properties of epoxy resin was investigated systematically by limiting oxygen index (LOI), cone calorimeter (Cone), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Compared to graphenit-ox, the addition of graphenit-Cu reduced the heat release rate (HRR), total smoke production (TSP) and smoke production rate (SPR), and improved LOI values of epoxy composites. Moreover, the addition of graphenit-ox also had little flame retardant effect on epoxy composite. The possible synergistic effect between graphene and Cu was confirmed in the flame retardant epoxy composites. TGA and DMA results also indicated the considerable effect on the thermal degradation and thermomechanical properties of epoxy composites with the addition of graphenit-Cu. The results supplied an effective solution for developing excellent flame retardant epoxy composites.

We report here a series of heavier alkaline earth metal complexes with N,N'-(ethane-1,2-diyl)bis(P,P-diphenylphosphinoselenoic amide) using two synthetic routes. In the first route, the heavier alkaline earth metal bis(trimethylsilyl)amides [M{N(SiMe3)2}2(THF)n] (M = Ca, Sr, Ba), when treated with phosphinoselenoic amine [Ph2P(Se)NHCH2CH2NHPPh2(Se)] (1), afforded the corresponding alkaline earth metal complexes of the composition [(THF)3M{Ph2P(Se)NCH2CH2NPPh2(Se)}] [M = Ca (2), Sr (3), Ba (4)]. The metal complexes 2-4 were also obtained from a one-pot reaction, where potassium phosphinoselenoic amide was generated in situ by the reaction of compound 1 and [KN(SiMe3)2], followed by the addition of the respective metal diiodides in THF at room temperature. The magnesium complex [(THF)3Mg{Ph2P(Se)NCH2CH2NPPh2(Se)}] (5) was also prepared. The solid-state structures of alkaline earth metal complexes 2-5 were established by single crystal X-ray diffraction analysis. In the solid state, all the metal complexes are monomeric but in complexes 2-4, ligand 1 is chelated in a tetra-dentate fashion to each metal ion but in complex 5, ligand 1 behaves as a bidentate ligand. Complexes 2-4 were tested as catalysts for the ring-opening polymerisation of ε-caprolactone and a high level of activity for the barium complex 4 was observed, with narrow polydispersity. We also report the synthesis and structure of the bis(amidophosphino borane) ligand [Ph2P(BH3)NHCH2CH2NHPPh2(BH3)] (6) and the corresponding barium complex [(THF)2Ba{Ph2P(BH3)NCH2CH2NPPh2(BH3)}]2 (7).

No abstract