Two-component thermoreversible hydrogels of melamine and gallic acid

A new two-component hydrogel of melamine and gallic acid is reported for three different compositions of the components. Optical and scanning electron microscopy indicate the fibrillar network structure of the gel, and the DSC study indicates a reversible first-order phase transition in the system. The storage modulus (G') versus frequency plot is linear and invariant at 35 and 50 °C but not at 70 °C, where it is in the sol state. The rheological melting point of 58 °C is close to the gel melting point obtained from DSC. The system shows a strong influence of pH on gelation. An FTIR study indicates H-bond formation between the >C-O group of gallic acid and the -NH2 group of melamine. 1H NMR spectra indicate the presence of π-π stacking in the gel. The UV-vis peak positions of gallic acid remain unaffected during complexation; however, the normalized absorption intensity is higher in the GM13 sol compared to that of other complexes. The photoluminescence (PL) spectra of the gels are interesting, showing a two-order increase in intensity in the gel state compared to that in the sol state. Three different structures of the complexes are proposed for the three different compositions of the components

Diversity in the Coordination Polymers of 2‑(2-(Pyridin-4/3-yl)vinyl)‑1<i>H</i>‑benzimidazole and Dicarboxylates/Disulfonates: Photochemical Reactivity and Luminescence Studies

Solvothermal reactions of Cd­(II) or Zn­(II) with two unsymmetrical olefinic ligands containing benzimidazole and 3-pyridyl/4-pyridyl moieties and ancillary anionic linkers such as dicarboxylates or disulfonates resulted in the coordination polymers containing diversified geometries. The crystal structure analyses of about eight such CPs reveal that the coordination networks found here include one-dimensional (1D) chains of metal and dicarboxylates/disulfonates with ligands as pendents, two-dimensional corrugated layers containing rectangular grids, and a three-dimensional (3D) coordination network. In two of the complexes, Cd₂O₂ acts as a secondary building unit (SBU) to form a two-dimensional (2D) layer of metal and dicarboxylates. The interdigitation of the pendent ligands of 1D-chains resulted in the required alignment of double bonds of <b>L</b>_<b>1</b> or <b>L</b>_<b>2</b> for photochemical [2 + 2] reaction, in two of the CPs. These CPs upon irradiation were found to undergo solid state [2 + 2] cycloaddition reactions with 100% conversion. All the complexes including irradiated ones were found to exhibit intense emission in solid state luminescence studies

Scalable, One-Pot, Microwave-Accelerated Tandem Synthesis of Unsymmetrical Urea Derivatives

We report a facile, microwave-accelerated, one-pot tandem synthesis of unsymmetrical ureas via a Curtius rearrangement. In this method, one-pot microwave irradiation of commercially available (hetero)­aromatic acids and amines in the presence of diphenylphosphoryl azide enabled extremely rapid (1–5 min) construction of an array of unsymmetrical ureas in good to excellent yields. We demonstrate the utility of our method in the efficient, gram-scale synthesis of key biologically active compounds targeting the cannabinoid 1 and α7 nicotinic acetylcholine receptors

Tuning Emission Properties via Aromatic Guest Inclusion in Organic Salts Composed of 4,4′-Dinitro-2,2′,6,6′-tetracarboxybiphenyl and Acridine

An organic salt composed of 4,4′-dinitro-2,2′,6,6′-tetracarboxybiphenyl and acridine has been shown to act as host to accommodate large polyaromatic guest molecules. Carboxylate–pyridinium hydrogen bonds, π–π and cation···π interactions are found to play a pivotal role in these host–guest complexes. All the complexes are found to exhibit distinct colors and photoluminescence which correlate with the charge-transfer interactions between acridinium ion and guest molecules, and ionization potential or donor ability of the guest molecules

EXCESS workshop: Descriptions of rising low-energy spectra

International audienceMany low-threshold experiments observe sharply rising event rates of yet unknown origins below a few hundred eV, and larger than expected from known backgrounds. Due to the significant impact of this excess on the dark matter or neutrino sensitivity of these experiments, a collective effort has been started to share the knowledge about the individual observations. For this, the EXCESS Workshop was initiated. In its first iteration in June 2021, ten rare event search collaborations contributed to this initiative via talks and discussions. The contributing collaborations were CONNIE, CRESST, DAMIC, EDELWEISS, MINER, NEWS-G, NUCLEUS, RICOCHET, SENSEI and SuperCDMS. They presented data about their observed energy spectra and known backgrounds together with details about the respective measurements. In this paper, we summarize the presented information and give a comprehensive overview of the similarities and differences between the distinct measurements. The provided data is furthermore publicly available on the workshop’s data repository together with a plotting tool for visualization