The complexation reactions of pyridine and benzimidazole containing olefin, namely, 2-(2-(pyridine-4-yl)- vinyl)-1H-benzimidazole (1), with aromatic mono-, di-, tri-, and tetra carboxylic acids resulted in the formation of cocrystals and salts. These studies are aimed at templating solid-state [2 + 2] reactions of olefin in head-to-tail geometry through cation−π interactions and studying their luminescence properties. Out of eight complexes synthesized, two are found to be cocrystals, and six are found to be salts. The formation of cocrystals was observed in the reactions of 1 with 4-hydroxybenzoic acid (HPHBA) and terephthalic acid (H2TA). The formation of salts was observed in the reactions of 1 with 4-nitrobenzoic acid (HPNBA), 4-aminobenzoic acid (HPABA), Na-5-sulfoisophthalate (H2SIP), trimesic acid (H3TMA), and pyromellitic acid (H4PMA). Given the presence of two basic sites in 1, in the form of pyridine and benzimidazole, the tricomponent reactions of 1 were carried out by considering any of the two acids from HPNBA, HPHBA, and HPABA. One tricomponent crystal formation was observed, interestingly with the combination of 1, HPHBA, and HPABA. Molecule 1 was found to exhibit segregated stacks of head-to-tail dimers of 1 in all these complexes with the exceptions of H3TMA and ternary complexes where the mixed stacking was observed. Four complexes were found to have the required alignment of the olefin moieties for solidstate [2 + 2] reactions. The solid-state luminescence studies indicate shifting of emission maxima with respect to that of 1 based on the stacking interactions in their crystal structures. Further, the ternary complex was shown to act as a colorimetric sensor for NH3 by switching of the color from orange to yellow, which can be reverted back upon exposure to HCl.<\/p>")"> Abstract

: A new class of organic polymers have been synthesized via solid-state [2 + 2] photopolymerization reaction of coordination polymers (CPs) of an angular diene, namely, 3,3′-(1,3-phenylene)bis(N-(3-pyridyl)- acrylamide) (L), with dicarboxylates as ancillary ligands. Five CPs of L have been studied, which includes three types of dicarboxylates and five metal ions such as Co(II), Cu(II), Cd(II), Ni(II), and Zn(II). Two of the three dicarboxylates contain angular (isophthalate\/glutarate) geometry and one contains linear geometry (terephthalate). The CPs with angular dicarboxylates exhibit 2D-layers containing M2L2 macrocycles, whereas the CPs with terephthalate exhibits 2D-corrugated layers containing rectangular grids. Four out of the five CPs are found to be photoreactive to produce coordination polymers of organic polymers (CPOPs) upon irradiation. The yields of solid state [2 + 2] polymerization reactions were calculated using 1 H NMR spectra and the degree of polymerization have been determined by MALDI-TOF mass spectra. Further, the CPs containing Cd(II) and Zn(II) (d10-configuration) were found to exhibit ligand based solid-state luminescence property. Whereas the CPs containing Co(II), Cu(II), and Ni(II) exhibited total quenching of luminescence of L due to the unpaired d-electronic configuration of the metal ions.<\/p>")"> Abstract

The dye encapsulated metal−organic frameworks (MOFs) are of interest for their practical applications such as light-emitting diodes, temperature sensing, and microlasers. However, very few MOFs have been reported to date where the dye moiety is utilized as one of the components of the framework. Fluorescein dye (FSD) doped materials have an ability to emit various colors such as red, green, and yellow depending upon their tautomeric form and external stimuli. In anticipation of light-emitting devices, three FSDbased novel MOFs, namely, {[Co2(FSD)2(H2O)4]·H2O·MeOH}n, FSDCo; {[Mn 2 (FSD) 2 ( H 2 O ) 4 ] · H 2 O · MeOH} n , FSDMn; and {[Cd2(FSD)2(H2O)3(MeOH)]·2(H2O)}n, FSDCd, have been designed and synthesized. These crystalline materials were shown to exhibit multicolor lightemitting behavior and reversible green to brown piezochromism, implying their potential to act as fluorescent switches, mechanosensors, and security papers. Further, these crystalline MOFs were also shown to exhibit a rare optical phenomenon called pleochroism. The green colored crystals displayed multiple colors under polarized light due to the agglomeration of nano- and microcrystals at different angles on the surface of macrocrystals.<\/p>")"> Abstract

Gel state reactions offer new direction for the reactivity of the organic molecules or metal?organic materials upon photoirradiation with shorter reaction times and high yields compared to solid and solution states. The restricted molecular movement among the molecules in the soft solids control the stereoselectivity of the photoproducts in the gel state reactions. To date, most of the strategies based on self?assembly have been demonstrated in the solid state, in particular for [2+2] reactions of olefins and polymerization reactions of diacetylenes via 1,4 addition. The soft materials are of emerging materials in recent days given their many applicative day?to?day aspects. This review gives a glimpse of recent reports on pericyclic reactions in the gel state that are designed based on the self?assembly concept. Also it highlights how such reactions accompany the physical changes in the structure of the gels and stereo controlled products with high yields.<\/p>")"> Abstract

N,N′-Bis(3-pyridylacrylamido) derivatives are shown to form cocrystals and salts with the dihalogens I2 and Br2. The detailed structural analyses of the cocrystals and salts reveal that the amide to amide N−H···O hydrogen bonding plays the major role in the cocrystals, while N−H···N hydrogen bonding predominates in the salts. With an increase in the halogen content in the lattice the interactions involved with halogens (N−H···X hydrogen bonding, N···X and X···X halogen bonding) are found to overpower the conventional N−H···O and N−H···N hydrogen bonding. In one such heavy halogen content salt, it is found that the water acts as a mere space-filling species and is not involved in any conventional hydrogen bonding such as N−H···N or N−H···O hydrogen bonds or halogen bonding. All of the cocrystals and salts are found to exhibit solid-state photoluminescence, which can be attributed to the charge transfer due to halogen bonding. Further, the tetrabrominated salts are found to exhibit phosphorescence at 77 K in a rigid matrix and also at room temperature owing to triplet-producing carbonyls and triplet-stabilizing heavy-atom perturbations (C−Br···Br−C, Br···Br, C−H···Br) in their crystal lattice.<\/p>")"> Abstract

Development of cost-effective and efficient non noble metal electrocatalysts has immense importance towards sustainable energy technologies. Herein, a newly constructed porous Co(II)-metal organic framework (MOF) has been utilized for the synthesis of cobalt nanoparticles embedded in N-doped porous carbon, (Co@NPC), via a facile MOF-annealing strategy, at an optimum temperature of 800 C under an argon atmosphere. DMF molecules present in the form of solvated guests and cations within the 3D-framework serve as a source for N-doping during the formation of the porous graphitic carbon upon carbonization. The nanocomposite was found to encapsulate homogeneously dispersed cobalt nanoparticles within the N-doped porous carbonaceous matrix. The synergistic effect of cobalt nanoparticles and the heteroatom-doped carbon framework makes Co@NPC electrochemically active towards both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) under alkaline conditions. Furthermore, Co@NPC exhibits outstanding performance as a bifunctional electrocatalyst towards electrochemical water splitting with remarkable stability and durability. It achieves a current density of 10 mA cm2 at a low cell voltage of 1.66 V in 1 M NaOH solution which is comparable with that of most of the self-templated ZIF-derived non-noble metal electrocatalysts.<\/p>")"> Abstract

Exploration of a new type of water-stable proton conducting material is of great interest owing to its applications as an electrolytic material in proton exchange membrane fuel cells (PEMFC). Herein, we report four such new metal organic frameworks of Cd(II) and Co(II) containing a new linear bis-pyridyltris-amide ligand (L) and angular dicarboxylates 4,4’-oxybisbenzoic acid (OBA) and benzene-1,3-diacrylic acid (BDA) as linkers. The MOFs are found to exhibit a general formula of {[M(L) (dicarboxylate)]·xDMF·yH2O}n with varying amounts of solvent. Two MOFs containing BDA exhibited twodimensional rectangular grid-like networks with grid dimensions of 25 × 23 Å2 , while those with OBA exhibited 3D-networks consisting of the mab topology with rectangular channels of dimensions 31 × 21 Å2 and 31 × 17 Å2 . All four exhibited a solvent accessible volume of 36–49%. AC impedance analyses on MOFs 1–4 reveal that they exhibit appreciable proton conductivities (PC): σ = 2.2 × 10−3 , 9.5 × 10−4 , 1.2 × 10−3 and 6.6 × 10−4 S cm−1 , respectively, at 353 K and 98% relative humidity (RH). The high PC values could be attributed to the hydrogen bonding between water molecules and also with amides and carboxylates of the framework. Furthermore, a gas sorption study revealed that MOFs 1–4 show preferential adsorption of water vapor (195–330 cc g−1 at p\/p0 ∼ 1) over nitrogen given the hydrophilic nature of the channels and the stability of MOFs under humid conditions. In addition, all these materials have shown capability in selectively adsorbing cationic dyes (methylene blue, MB and crystal violet, CV).<\/p>")"> Abstract