Polymorphic Phases of Supramolecular Liquid Crystal Complexes Laterally Substituted with Chlorine

New supramolecular complexes, based on H-bonding interactions between 4-(pyridin-4-yl) azo-(2-chlorophenyl) 4-alkoxybenzoates (Bn) and 4-[(4-(n-hexyloxy)phenylimino)methyl]benzoic acid (A6), were prepared and their thermal and mesomorphic properties investigated via differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FT-IR) in order to confirm their H-bonding interactions. The mesophase behavior of each mixture was examined by DSC and polarized optical microscopy (POM). According to the findings of the study, in all of the designed mixtures, the introduction of laterally polar chlorine atom to the supramolecular complexes produces polymorphic compounds possessing smectic A, smectic C and nematic mesophases, in addition, all products have low melting transitions. Thermal stabilities of the associated phases depend on the position and orientation of the lateral polar Cl− atom as well as the length of terminal flexible alkoxy chain. Comparisons were made between the present lateral Cl− complexes and previously investigated laterally-neat complexes in order to investigate the impact of the addition, nature and orientation of polar substituent on the mesomorphic behavior. The investigations revealed that, the polarity and mesomeric nature of inserted lateral substituent into the base component play an essential role in affecting their mesomorphic properties. Furthermore, for current complexes, induced polymorphic phases have been found by introducing the chlorine atom.

Low-temperature crystal structure of 4-chloro-1H-pyrazole

The structure of 4-chloro-1H-pyrazole, C3H3ClN2, at 170 K has orthorhombic (Pnma) symmetry and is isostructural to its bromo analogue. Data were collected at low temperature since 4-chloro-1H-pyrazole sublimes when subjected to the localized heat produced by X-rays. The structure displays intermolecular N—H...N hydrogen bonding and the packing features a trimeric molecular assembly bisected by a mirror plane (m normal to b) running through one chlorine atom, one carbon atom and one N—N bond. The asymmetric unit therefore consists of one and one-half 4-chloro-1H-pyrazole molecules. Thus, the N—H proton is crystallographically disordered over two positions of 50% occupancy each.

Hybrid Xerogels: Study of the Sol-Gel Process and Local Structure by Vibrational Spectroscopy

The properties of hybrid silica xerogels obtained by the sol-gel method are highly dependent on the precursor and the synthesis conditions. This study examines the influence of organic substituents of the precursor on the sol-gel process and determines the structure of the final materials in xerogels containing tetraethyl orthosilicate (TEOS) and alkyltriethoxysilane or chloroalkyltriethoxysilane at different molar percentages (RTEOS and ClRTEOS, R = methyl [M], ethyl [E], or propyl [P]). The intermolecular forces exerted by the organic moiety and the chlorine atom of the precursors were elucidated by comparing the sol-gel process between alkyl and chloroalkyl series. The microstructure of the resulting xerogels was explored in a structural theoretical study using Fourier transformed infrared spectroscopy and deconvolution methods, revealing the distribution of (SiO)4 and (SiO)6 rings in the silicon matrix of the hybrid xerogels. The results demonstrate that the alkyl chain and the chlorine atom of the precursor in these materials determines their inductive and steric effects on the sol-gel process and, therefore, their gelation times. Furthermore, the distribution of (SiO)4 and (SiO)6 rings was found to be consistent with the data from the X-Ray diffraction spectra, which confirm that the local periodicity associated with four-fold rings increases with higher percentage of precursor. Both the sol-gel process and the ordered domains formed determine the final structure of these hybrid materials and, therefore, their properties and potential applications.

Mono- and Diamination of 4,6-Dichloropyrimidine, 2,6-Dichloropyrazine and 1,3-Dichloroisoquinoline with Adamantane-Containing Amines

N-heteroaryl substituted adamantane-containing amines are of substantial interest for their perspective antiviral and psychotherapeutic activities. Chlorine atom at alpha-position of N-heterocycles has been substituted by the amino group using convenient nucleophilic substitution reactions with a series of adamantylalkylamines. The prototropic equilibrium in these compounds was studied using NMR spectroscopy. The introduction of the second amino substituent in 4-amino-6-chloropyrimidine, 2-amino-chloropyrazine, and 1-amino-3-chloroisoquinoline was achieved using Pd(0) catalysis.

Structure and germicidal property of a novel guanidine organomercury complex

A novel guanidine organomercury complex 1, [HgCl(DNP)]·CH5N3·CH3CN 1 (DNP = 2,4- dinitrophenol), has been synthesized. Each mercury(II) atom is tricoordinated to one chlorine atom, one carbon atom of the benzene ring, and one oxygen atom from 2, 4-dinitrophenol. The coordination arrangement around the mercury atom is Y-shaped. This is the first structural report on an organomercury derivative of 2, 4-dinitrophenol and guanidine. The distance of Hg-Cl between the two Hg ions groups is 3.272 Å, which indicates the presence of weak Hg···Cl interactions. Secondary bonds make complex 1 form 3D interspersed network structure, which is 2D [HgCl(DNP)CH5N3]n plane and 1D solvent [(CH3CN)2]∞ broadband. The antibacterial activity of 1 were studied. It shows complex 1 has very good bactericidal activity, and is also a potential antimicrobial agents.

Bousmekines A-E, New Alkaloids from Two Bousigonia Species: B.angustifolia and B. mekongensis

Four new monoterpenoid indole alkaloids, bousmekines A-D (1–4), and one new pyranopyridine alkaloid, bousmekine E (5), were isolated from the twigs and leaves of Bousigonia angustifolia and Bousigonia mekongensis. Their structures including absolute configurations were elucidated by a combination of MS, NMR, ECD calculation, and single-crystal X-ray diffraction analysis. Compound 2 was an eburnea-type MIAs characterized by a rare chlorine atom while 5 possessed a novel pyranopyridine moiety. Their cytotoxicities against several human cancer cell lines were evaluated and compound 1 exhibited significant cytotoxicity with IC50 values of 0.8–7.4 μM. Graphic Abstract