No abstract

Direct observation of gas molecules confined in the nanospace of porous materials by single-crystal X-ray diffraction (SXRD) technique is significant because it leads to deep insight into the adsorption mechanism and the actual state of the adsorbents in molecular level. A recent study revealed that flexibility is one of the important factors to achieve periodic guest accommodation in the nanospace enabling direct observation of gas molecules. Here, we report a convenient strategy to tune the framework flexibility by just an atomic exchange in a ligand, which enables us to easily construct a soft nanospace as the best platform to study gas adsorption. Indeed, we succeeded to observe C2H2 and CO2 molecules confined in the pores of a flexible porous coordination polymer (PCP-N) in different configurations using SXRD measurement, whereas gas molecules in a rigid framework (PCP-C) isostructural to PCP-N were not seen crystallographically. The result of the coincident in situ powder X-ray diffraction and adsorption measurement for PCP-N unambiguously showed that the framework could flexibly transform to trap gas molecules with a commensurate fashion. In addition, for PCP-N, we found that the adsorbed gas molecules induced significant structural change involving dimensional change of the pore from one-dimensional to three-dimensional, and subsequently, additional gas molecules formed periodic molecular clusters in the nanospace.

A recoverable photo-polymerization catalyst based on an imidazolium and a polyoxometalate, viz., (BMIm)2(DMIm)PW12O40 (where, BMIm = 1-butyl-3-methylimidazolium, DMIm = 3,3'-dimethyl-1,1'-diimidazolium) is reported. It catalyzes photo-polymerization of several industrially important monomers like styrene, methyl methacrylate, butyl methacrylate and vinyl acetate. The catalyst is recoverable and hence can be reused. The molecular weight and polydispersity index can be controlled reasonably and a reaction pathway is proposed. The synthesis of this novel catalyst is reported and the catalyst has been characterized using standard techniques such as single crystal X-ray diffraction studies, cyclic voltammetry and various spectroscopic methods such as Fourier transform infrared spectroscopy, (1)H NMR spectroscopy, EPR spectroscopy and UV-Vis spectroscopy. DFT calculations have been used to explain the catalyst's photo-chemical activity.

Reactions of N-diphenylphosphanylmethyl-4-aminopyridine (dppmapy) with K[Ag(CN)(2)], Ag(dca) (dca = dicyanamide), AgSCN, AgCl, AgBr or AgI gave rise to six [Ag(2)X(2)]-based (X = CN(-), dca, SCN(-), Cl(-), Br(-) and I(-)) compounds, [{Ag(2)(CN)(2)(dppmapy)}.0.5CHCl(3)](n) (1), [Ag(2)L(2)(dppmapy)(2)](n) (2: L = dca; 3: L = SCN), [{Ag(2)L(2)(dppmapy)(2)}.sol](n) (4: L = Cl, sol = 0.5MeOH.0.5CH(2)Cl(2); 5: L = Br, sol = 2CHCl(3)), and [Ag(2)I(2)(dppmapy)(4)].3MeOH (6). Complexes 1-6 were characterized by elemental analysis, IR, powder X-ray diffraction (PXRD), and single crystal X-ray diffraction. Compound 1 has a one-dimensional (1D) spiral chain constructed by bridging the [(CN)Ag(mu-CN)Ag] fragments via dppmapy ligands. In 2, 3 and 4, each [Ag(2)X(2)] (X = dca, SCN, Cl) fragment is linked by dppmapy bridges to the other two equivalent ones to form a 1D chain containing 16-membered rings (2) or a 1D double chain containing 20-membered rings (3) or a 1D spiral chain containing 20-membered rings (4). Compound 5 possesses a two dimensional (2D) (4,4) network consisting of 36-membered metallomacrocycles in which each [Ag(2)Br(2)] fragment acts as a unique planar four-connecting node to link the other four equivalent ones via dppmapy bridges. Complex 6 has a [Ag(2)I(2)] unit with a pair of monodentate dppmapy ligands coordinated at each Ag center. The photoluminescent properties of 1-6 in the solid state at ambient temperature were also investigated.

A wheel-like hexadecanuclear cobalt phosphonate [Co(16)(OH)(6)(chp)(22)(O(3)PC(6)H(9))(2)(H(2)O)(4)] has been synthesized by reactions of cobalt perchlorate with cyclohexenephosphonic acid (H(2)O(3)PC(6)H(9)) and 6-chloro-2-hydroxypyridine (Hchp) in the presence of Et(3)N. Magnetic studies on the compound show a general decline of chi(M)T with decreasing T. The appeared maximum of chi(M)T at low temperature suggests the presence of a non-diamagnetic ground state. The alternating current susceptibilities show frequency-dependent signals.