6-Chloro-3-[(di-methyl-amino)-methyl-idene]thio-chroman-4-one.

The asymmetric unit of the title compound, C12H12ClNOS, contains three independent mol-ecules, with the thio-chroman ring adopting a sofa conformation in each one. The crystal structure features C-H⋯O inter-actions; one of the O atoms accepts three such bonds. Together, the hydrogen bonds give rise to a molecular tape propagating in [010].

2-Amino-4-methyl-4,5,6,7-tetrahydro-1-benzothiophene-3-carbonitrile.

In the title compound, C(10)H(12)N(2)S, the thio-phene ring is essentially planar (r.m.s. deviation = 0.0290 Å). The two C atoms of the cyclo-hexene ring (at positions 6 and 7) are disordered over two sets of sites in a 0.810 (5):0.190 (5) ratio. The cyclo-hexene rings in both the major and minor occupancy conformers adopt a half-chair conformation. In the crystal, there are two types of N-H⋯N inter-action. One of these results in centrosymmetric head-to-head dimers corresponding to an R(2) (2)(12) graph-set motif and the other forms a 20-membered macrocyclic ring involving six mol-ecules.

4-Imino-2,7-dimethyl-5,6,7,8-tetra-hydro-4H-1-benzothieno[2,3-d]pyrimidin-3-amine.

In the title compound, C(12)H(16)N(4)S, the fused benzothio-phene and the pyrimidine rings are coplanar [dihedral angle = 1.61 (6)°]. Three C atoms of the cyclohexene ring (at positions 3, 6 and 7) are disordered over two sites with an occupancy ratio of 0.702 (8):0.298 (8). The cyclo-hexene ring in both the major and minor components adopts a half-chair conformation. The crystal structure is stabilized by N-H⋯N and C-H⋯N inter-actions, resulting in the formation of inversion dimers with R(2) (2)(10) and R(2) (2)(12) graph-set motifs.

1-(2-Chloro-eth-yl)-1H-pyrazolo-[3,4-d]pyrimidin-4(5H)-one.

In the title compound, C(7)H(7)ClN(4)O, the pyrazolo-pyrimidine ring is essentially planar, the r.m.s. deviation of the fitted atoms being 0.0071 Å. The crystal structure features strong N-H⋯O hydrogen bonds and further consolidated by weak C-H⋯O, C-H⋯N and C-H⋯Cl inter-actions.

7-Methyl-5,6,7,8-tetra-hydro-1-benzo-thieno[2,3-d]pyrimidin-4-amine.

In the title compound, C(11)H(13)N(3)S, two of the C atoms of the cyclo-hexene ring and the methyl group attached to it are disordered over two sets of sites in a 0.544 (2):0.456 (2) ratio. The benzothiene and pyrimidine rings are almost coplanar with an angular tilt of 2.371 (9)° between them. The thio-phene ring is essentially planar (r.m.s. deviation 0.05 Å), while the cyclo-hexene ring in both the major- and minor-occupancy conformers adopts a half-chair conformation. In the crystal structure, pairs of intermolecular N-H⋯N hydrogen bonds involving the amino groups result in centrosymmetric head-to-head dimers about inversion centres, corresponding to an R(2) (2)(8) graph-set motif. Further, N-H⋯N hydrogen bonding generates a two-dimensional hydrogen-bonded network perpendicular to the ac plane and running along the diagonal of the ac plane.

2-Phenyl-8,9,10,11-tetra-hydro-1-benzo-thieno[3,2-e][1,2,4]triazolo[1,5-c]pyrimidine.

In the title compound, C(17)H(14)N(4)S, the benzothieno moiety is fused at one end of the pyramidine ring while the triazole ring with a phenyl substituent is fused at the other side. The triazole ring is almost planar [maximum deviation = 0.0028 (3) Å] while the cyclo-hexane ring adopts a half-chair conformation. In the crystal, pairs of inter-molecular C-H⋯N hydrogen bonds form centrosymmetric head-to-head dimers, corresponding to an R(2) (2)(8) graph-set motif. Further C-H⋯N inter-actions generate a zigzag chain of mol-ecules along the c axis. The supra-molecular assembly is consolidated by π-π stacking inter-actions [centroid-centroid distance = 3.445 (4) Å].

6-(4-Bromo-phen-yl)-2-(4-fluoro-benz-yl)imidazo[2,1-b][1,3,4]thia-diazole.

In the title compound, C(17)H(11)BrFN(3)S, the imidazothia-diazole and bromo-phenyl rings are individually almost planar, with maximum deviations of 0.0215 (4) and 0.0044 (4) Å, respectively, and are inclined at an angle of 27.34 (3)° with respect to each other. The dihedral angle between the mean planes of the fluoro-benzyl and imidazothia-diazole rings is 79.54 (3)°. The crystal structure is stabilized by inter-molecular C-H⋯N inter-actions resulting in chains of mol-ecules along the b axis.

3-{[6-(4-Chloro-phen-yl)imidazo[2,1-b][1,3,4]thia-diazol-2-yl]meth-yl}-1,2-benzoxazole.

In the title compound, C(18)H(11)ClN(4)OS, the benzisoxazole and imidazothia-diazole rings are inclined at an angle of 23.81 (7)° with respect to each other. The imidazothia-diazole and chloro-phenyl rings make a dihedral angle of 27.34 (3)°. In the crystal, inter-molecular C-H⋯N inter-actions generate a chain along the c axis and C-H⋯O inter-actions form centrosymmetric dimers resulting in an R(2) (2)(26) graph-set motif. Moreover, the C-H⋯N and S⋯N [3.206 (4) Å] inter-actions links the mol-ecules into R(7) ring motifs. The packing is further stabilized by π-π stacking inter-actions between the thia-diazole rings with a shortest centroid-centroid distance of 3.497 (3) Å. In addition, C-H⋯π inter-actions are observed in the crystal structure.

2-Amino-6-methyl-4,5,6,7-tetra-hydro-1-benzothio-phene-3-carbonitrile.

In the title compound, C(10)H(12)N(2)S, one of the C atoms of the cyclo-hexene ring (at position 6) and the methyl group attached to it are disordered over two sets of sites in a 0.650 (3):0.350 (3) ratio. The cyclo-hexene ring in both the major and minor occupancy conformers adopts a half-chair conformation. The thio-phene ring is essentially planar (r.m.s. deviation = 0.05 Å). In the crystal, N-H⋯N hydrogen bonds involving the amino groups result in inversion dimers with R(2) (2)(12) graph-set motif. Further N-H⋯N hydrogen bonds involving the amino and carbonitrile groups generate zigzag chains along the a axis.

3-{[5-(4-Bromo-phen-yl)imidazo[2,1-b][1,3,4]thia-diazol-2-yl]meth-yl}-1,2-benzoxazole.

In the title compound, C(18)H(11)BrN(4)OS, the imidazothia-diazole and benzisoxazole rings are individually planar with maximum deviations of 0.025 (3) 0.015 (4) Å, respectively, and are inclined at an angle of 23.51 (7)° with respect to each other. The planes of the imidazothia-diazole and bromo-phenyl rings are inclined at an angle of 27.34 (3)°. In the crystal, inter-molecular C-H⋯N inter-actions result in chains of mol-ecules along the b and c axes. Moreover, C-H⋯O inter-actions result in centrosymmetric head-to-head dimers with R(2) (2)(24) graph-set motifs. The mol-ecular packing is further stabilized by π-π stacking inter-actions between the imidazole rings with a shortest centroid-centroid distance of 3.492 (3) Å. In addition, C-H⋯π inter-actions are observed in the crystal structure.

2-Amino-7-oxo-4,5,6,7-tetra-hydro-1-benzothio-phene-3-carbonitrile.

In the title compound, C(9)H(8)N(2)OS, the benzothio-phene ring is substituted with amino, oxo and carbonitrile groups. The thio-phene ring is essentially planar (r.m.s. deviation = 0.0003 Å), while the cyclo-hexene ring is in a half-chair conformation. In the crystal, N-H⋯O hydrogen bonds generate chains of mol-ecules in a zigzag pattern along the b axis. Pairs of N-H⋯N hydrogen bonds form centrosymmetric head-to-head dimers about inversion centres, corresponding to an R(2) (2)(12) graph-set motif. In addition, rather weak N-H⋯S inter-actions are also present in the structure and the supra-molecular assembly is further consolidated by π-π stacking inter-actions between the benzothio-phene rings, disposed at a distance of 3.742 (3) Å.

Molecularly controlled metal-semiconductor junctions on silicon surface: a dipole effect.

Silicon surface was chemically modified by covalent attachment of homologous organic molecules having different dipole moments. Surface photovoltage measurements clearly confirm that organic molecules have a profound effect on surface band bending of semiconductor. Metal-molecules--silicon junctions were constituted for molecules belonging to ethynylbenzene series using soft mercury contact. These junctions show a systematic change in the electrical charge transport with dipole moment of molecules. Parameters such as ideality factor, barrier height, and density of interface states of various junctions are estimated to understand the role of organic molecules. These studies offer the prospect to develop molecular electronics, which may find potential applications in solar cells and chemical and biological sensors.

Synthesis and biological activity of some 3-methyl/ethoxycarbonyl-6-arylimidazo[2, 1-b]thiazoles and their 5-bromo/5-formyl derivatives

Facile reaction of arylacylbromide 1 with 2-amino-4-methylthiazole 2 and its hindered reaction with 2-amino-4-ethoxycarbonylthiazole 3 during the synthesis of 3-methyl/ethoxycarbonyl-6-arylimidazo[2,1-b]thiazoles 8/9 are explained on the basis of electronic effects of the 4-substituent of thiazole substrate. Their bromination/formylation afforded the corresponding 5-bromo and 5-formyl derivatives. Results of preliminary screening of the target compounds reveal moderate anthelmintic and anti-inflammatory activity.