Molecular structure and selective theophylline complexation by conformational change of diethyl N,N'-(1,3-phenylene)dicarbamate.

The receptor ability of diethyl N,N'-(1,3-phenylene)dicarbamate (1) to form host-guest complexes with theophylline (TEO) and caffeine (CAF) by mechanochemistry was evaluated. The formation of the 1-TEO complex (C12H16N2O4·C7H8N4O2) was preferred and involves the conformational change of one of the ethyl carbamate groups of 1 from the endo conformation to the exo conformation to allow the formation of intermolecular interactions. The formation of an N-H...O=C hydrogen bond between 1 and TEO triggers the conformational change of 1. CAF molecules are unable to form an N-H...O=C hydrogen bond with 1, making the conformational change and, therefore, the formation of the complex impossible. Conformational change and selective binding were monitored by IR spectroscopy, solid-state 13C nuclear magnetic resonance and single-crystal X-ray diffraction. The 1-TEO complex was characterized by IR spectroscopy, solid-state 13C nuclear magnetic resonance, powder X-ray diffraction and single-crystal X-ray diffraction.

Indolealkylamines in the venom of the scorpion Thorellius intrepidus.

Scorpions are a group of arthropods that strike fear in many people due to their severe medical symptoms, even death, caused by their venomous stings. Even so, not all scorpion species contain harmful venoms against humans but still have valuable bioactive molecules, which could be used in developing new pharmaceutical leads for treating important diseases. This work conducted a comprehensive analysis of the venom from the scorpion Thorellius intrepidus. The venom of T. intrepidus was separated by size exclusion chromatography, and four main fractions were obtained. Fraction IV (FIV) contained small molecules representing over 90% of the total absorbance at 280 nm. Analysis of fraction FIV by RP-HPLC indicated the presence of three main molecules (FIV.1, FIV.2, and FIV.3) with similar UV absorbance spectra profiles. The molecular masses of FIV.1, FIV.2, and FIV.3 were determined, resulting in 175.99, 190.07, and 218.16 Da, respectively. Further confirmation through 1H-NMR and 13C-NMR analyses revealed that these molecules were serotonin, N-methylserotonin, and bufotenidine. These intriguing compounds are speculated to play a pivotal role in self-defense and increasing venom toxicity and could also offer promising biotechnological applications as small bioactive molecules.

Crystal structure and characterization of the sulfamethazine-piperidine salt.

Sulfamethazine [N1-(4,6-dimethylpyrimidin-2-yl)sulfanilamide] is an antimicrobial drug that possesses functional groups capable of acting as hydrogen-bond donors and acceptors, which make it a suitable supramolecular building block for the formation of cocrystals and salts. We report here the crystal structure and solid-state characterization of the 1:1 salt piperidinium sulfamethazinate (PPD+·SUL-, C5H12N+·C12H13N4O2S-) (I). The salt was obtained by the solvent-assisted grinding method and was characterized by IR spectroscopy, powder X-ray diffraction, solid-state 13C NMR spectroscopy and thermal analysis [differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA)]. Salt I crystallized in the monoclinic space group P21/n and showed a 1:1 stoichiometry revealing proton transfer from SUL to PPD to form salt I. The PPD+ and SUL- ions are connected by N-H+...O and N-H+...N interactions. The self-assembly of SUL- anions displays the amine-sulfa C(8) motif. The supramolecular architecture of salt I revealed the formation of interconnected supramolecular sheets.

Crystal structure of the chalcone (E)-3-(furan-2-yl)-1-phenylprop-2-en-1-one.

The title chalcone derivative, C13H10O2, adopts an E conformation about the C=C double bond. The mol-ecule is composed of a furanyl and a phenyl ring, bridged by an α,ß-unsaturated carbonyl system, which are inclined to one another by 24.07 (7)°. In the crystal, mol-ecules are connected by weak C-H⋯O hydrogen bonds involving the carbonyl O atom acting as a trifurcated acceptor and C-H⋯π inter-actions, forming ribbons extending along the c-axis direction.

Exo conformers of N-(pyridin-2-yl)- and N-(pyridin-3-yl)norbornene-5,6-dicarboximide crystals.

Two isomeric pyridine-substituted norbornenedicarboximide derivatives, namely N-(pyridin-2-yl)-exo-norbornene-5,6-dicarboximide, (I), and N-(pyridin-3-yl)-exo-norbornene-5,6-dicarboximide, (II), both C(14)H(12)N(2)O(4), have been crystallized and their structures unequivocally determined by single-crystal X-ray diffraction. The molecules consist of norbornene moieties fused to a dicarboximide ring substituted at the N atom by either pyridin-2-yl or pyridin-3-yl in an anti configuration with respect to the double bond, thus affording exo isomers. In both compounds, the asymmetric unit consists of two independent molecules (Z' = 2). In compound (I), the pyridine rings of the two independent molecules adopt different conformations, i.e. syn and anti, with respect to the methylene bridge. The intermolecular contacts of (I) are dominated by C-H...O interactions. In contrast, in compound (II), the pyridine rings of both molecules have an anti conformation and the two independent molecules are linked by carbonyl-carbonyl interactions, as well as by C-H...O and C-H...N contacts.

exo-1,7-Dimethyl-4-phenyl-10-oxa-4-aza-tri-cyclo-[5.2.1.0(2,6)]dec-8-ene-3,5-dione.

The title compound, C16H15NO3, consists of an oxabicycle fused to an N-phenyl-substituted pyrrolidine ring anti to the double bond, affording the exo isomer. In the oxabicycle system, the six-membered ring presents a boat conformation, while the heterocyclic rings show envelope conformations with the O atom projected out of the plane. In the crystal, adjacent mol-ecules are linked via weak C-H⋯O hydrogen bonds, forming chains propagating along the a-axis direction. The chains are linked by C-H⋯π inter-actions, forming two-dimensional networks lying parallel to the ac plane.

(E)-1-([1,1'-Biphen-yl]-4-yl)-2-(1,3,3-tri-methylindolin-2-yl-idene)ethanone.

The title compound, C(25)H(23)NO, consists of a biphenyl-4-carbonyl unit attached to an exocyclic double bond group at position 2 of an indole unit, which presents methyl groups as substituents at positions 1 and 3. The mol-ecular conformation is s-cis with an E configuration, supported by weak intra-molecular C-H⋯O contacts involving the methyl groups and the carbonyl function. The rings of the biphenyl group are twisted by 37.13 (5)°. In the crystal, C-H⋯O and C-H⋯π inter-actions link the molecules.