Peculiar orientational disorder in 4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP) leading to bipolar crystals.

180° orientational disorder of molecular building blocks can lead to a peculiar spatial distribution of polar properties in molecular crystals. Here we present two examples [4-bromo-4'-nitrobiphenyl (BNBP) and 4-bromo-4'-cyanobiphenyl (BCNBP)] which develop into a bipolar final growth state. This means orientational disorder taking place at the crystal/nutrient interface produces domains of opposite average polarity for as-grown crystals. The spatial inhomogeneous distribution of polarity was investigated by scanning pyroelectric microscopy (SPEM), phase-sensitive second harmonic microscopy (PS-SHM) and selected volume X-ray diffraction (SVXD). As a result, the acceptor groups (NO2 or CN) are predominantly present at crystal surfaces. However, the stochastic process of polarity formation can be influenced by adding a symmetrical biphenyl to a growing system. For this case, Monte Carlo simulations predict an inverted net polarity compared with the growth of pure BNBP and BCNBP. SPEM results clearly demonstrate that 4,4'-dibromobiphenyl (DBBP) can invert the polarity for both crystals. Phenomena reported in this paper belong to the most striking processes seen for molecular crystals, demonstrated by a stochastic process giving rise to symmetry breaking. We encounter here further examples supporting the general thesis that monodomain polar molecular crystals for fundamental reasons cannot exist.

Crystal structure of 2,4,6-tris-(cyclo-hex-yloxy)-1,3,5-triazine.

The title compound, C21H33N3O3, is a tri-substituted cyclo-hex-yloxy triazine. In the crystal, the triazine rings form (C3i-PU) Piedfort units. The inter-centroid distance of the π-π inter-action involving the triazine rings is 3.3914 (10) Å. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming ribbons propagating along [1-10]. There are also weak C-H⋯N and C-H⋯O contacts present, linking inversion-related ribbons, forming a three-dimensional structure.

A dinuclear cadmium(II) Schiff base thiocyanato complex: crystal structure and fluorescence.

A new dinuclear cadmium(II) complex, [Cd(L)(NCS)]2 (1) has been synthesized using a potentially tetradentate Schiff base ligand HL, 2-((E)-(2-(diethylamino)ethylimino)methyl)-6-methoxyphenol, obtained by the condensation of 2-diethylaminoethylamine and o-vanillin, and characterized by different physicochemical techniques. Crystal structure of the title complex was unambiguously established by single crystal X-ray diffraction which reveals that metal centers are connected by bridging phenolato and chelating methoxy oxygen atoms of the coordinating Schiff bases and embedded in severely distorted octahedral geometries. Fluorescence properties of the ligand and its complex, studied at room temperature indicate that later may serve as strong fluorescent emitter.

Synthesis, characterization and pharmacological study of 4,5-dihydropyrazolines carrying pyrimidine moiety.

A series of 5-bromo-2-(3,5-diaryl-4,5-dihydro-1H-pyrazol-1-yl)pyrimidine were prepared under conventional heating as well as microwave reaction condition. The newly synthesized compounds were characterized on the basis of elemental, spectral and single crystal X-ray studies. These new compounds were screened for their antioxidant, anti-inflammatory and analgesic activities. Some of these compounds exhibited potent biological activities compared to the standard drug.

4-{[Bis(2-hy-droxy-eth-yl)amino]-meth-yl}-6-meth-oxy-2H-chromen-2-one.

In the title compound, C(15)H(19)NO(5), an intra-molecular O-H⋯O hydrogen bond links the hy-droxy-ethyl side chains, forming a seven-membered ring. In the crystal, mol-ecules are linked into chains via O-H⋯O hydrogen bonds along the b axis. Further, mol-ecules are linked by weak inter-molecular C-H⋯O and π-π stacking inter-actions [centroid-centroid distance = 3.707 (4) Å].

Gel sculpture: moldable, load-bearing and self-healing non-polymeric supramolecular gel derived from a simple organic salt.

An easy access to a library of simple organic salts derived from tert-butoxycarbonyl (Boc)-protected L-amino acids and two secondary amines (dicyclohexyl- and dibenzyl amine) are synthesized following a supramolecular synthon rationale to generate a new series of low molecular weight gelators (LMWGs). Out of the 12 salts that we prepared, the nitrobenzene gel of dicyclohexylammonium Boc-glycinate (GLY.1) displayed remarkable load-bearing, moldable and self-healing properties. These remarkable properties displayed by GLY.1 and the inability to display such properties by its dibenzylammonium counterpart (GLY.2) were explained using microscopic and rheological data. Single crystal structures of eight salts displayed the presence of a 1D hydrogen-bonded network (HBN) that is believed to be important in gelation. Powder X-ray diffraction in combination with the single crystal X-ray structure of GLY.1 clearly established the presence of a 1D hydrogen-bonded network in the xerogel of the nitrobenzene gel of GLY.1. The fact that such remarkable properties arising from an easily accessible (salt formation) small molecule are due to supramolecular (non-covalent) interactions is quite intriguing and such easily synthesizable materials may be useful in stress-bearing and other applications.

(2E)-1-(5-Chloro-thio-phen-2-yl)-3-(2,3-dimeth-oxy-phen-yl)prop-2-en-1-one.

In the title compound, C(15)H(13)ClO(3)S, the chloro-thio-phene and dimeth-oxy-phenyl groups are linked by a prop-2-en-1-one group. The C=C double bond exhibits an E conformation. The mol-ecule is non-planar, with a dihedral angle of 31.12 (5)° between the chloro-thio-phene and dimeth-oxy-phenyl rings. The meth-oxy group at position 3 is coplanar with the benzene ring to which it is attached, with a C-O-C-C torsion angle of -3.8 (3)°. The meth-oxy group attached at position 2 of the benzene ring is in a (+)synclinal conformation, as indicated by the C-O-C-C torsion angle of -73.6 (2)°. In the crystal, two different C-H⋯O inter-molecular inter-actions generate chains of mol-ecules extending along the b axis.

4-Hy-droxy-6-(4-meth-oxy-phen-yl)-4-phenyl-1,3-diazinane-2-thione.

In the title compound, C(17)H(18)N(2)O(2)S, the 1,3-diazinane-2-thione ring system is not coplanar with the benzene ring and meth-oxy-phenyl ring system, the dihedral angle between the planes being 65.58 (13) and 89.18 (10)°, respectively. The crystal structure is characterized by inter-molecular O-H⋯S, N-H⋯S, N-H⋯O and C-H⋯S hydrogen bonding.

Bis{2-[4-(methyl-sulfan-yl)phen-yl]-1H-benzimidazol-3-ium} tetra-bromido-cuprate(II) dihydrate.

The asymmetric unit of the title compound, (C(14)H(13)N(2)S)(2)[CuBr(4)]·2H(2)O, contains two cations, one anion and two solvent water mol-ecules that are connected via O-H⋯Br, N-H⋯Br and N-H⋯O hydrogen bonds into a two-dimensional polymeric structure. The cations are arranged in a head-to-tail fashion and form stacks along [100]. The central Cu(II) atom of the anion is in a distorted tetra-hedral environment.

2-(4-Methyl-sulfanylphen-yl)-1H-benzimidazol-3-ium bromide.

In the cation of the title compound, C(14)H(13)N(2)S(+)·Br(-), the essentially planar benzimidazole system (r.m.s. deviation = 0.0082 Å) is substituted with a 4-methyl-sulfanylphenyl ring. The dihedral angle between the benzimidazole system and the 4-methyl-sulfanylphenyl ring is 2.133 (2)°. The crystal structure is characterized by strong and highly directional inter-molecular N-H⋯Br hydrogen bonds involving the bromide ion. Moreover, C-H⋯S inter-actions result in chains of mol-ecules along the c axis. The supra-molecular assembly is further stabilized by π-π stacking inter-actions between the benzimidazole system and 4-methyl-sulfanylphenyl rings [centroid-centroid distance = 3.477 (4) Å].

Chiral gels derived from secondary ammonium salts of (1R,3S)-(+)-camphoric acid.

In order to have access to chiral gels, a series of salts derived from (1R,3S)-(+)-camphoric acid and various secondary amines were prepared based on supramolecular synthon rationale. Out of seven salts prepared, two showed moderate gelation abilities. The gels were characterized by differential scanning calorimetry, table top rheology, scanning electron microscopy, single crystal and powder X-ray diffraction. Structure property correlation based on X-ray diffraction techniques remain inconclusive indicating that some of the integrated part associated with the gelation phenomena requires a better understanding.