Tunable porous organic crystals: structural scope and adsorption properties of nanoporous steroidal ureas.

Previous work has shown that certain steroidal bis-(N-phenyl)ureas, derived from cholic acid, form crystals in the P6(1) space group with unusually wide unidimensional pores. A key feature of the nanoporous steroidal urea (NPSU) structure is that groups at either end of the steroid are directed into the channels and may in principle be altered without disturbing the crystal packing. Herein we report an expanded study of this system, which increases the structural variety of NPSUs and also examines their inclusion properties. Nineteen new NPSU crystal structures are described, to add to the six which were previously reported. The materials show wide variations in channel size, shape, and chemical nature. Minimum pore diameters vary from ~0 up to 13.1 Å, while some of the interior surfaces are markedly corrugated. Several variants possess functional groups positioned in the channels with potential to interact with guest molecules. Inclusion studies were performed using a relatively accessible tris-(N-phenyl)urea. Solvent removal was possible without crystal degradation, and gas adsorption could be demonstrated. Organic molecules ranging from simple aromatics (e.g., aniline and chlorobenzene) to the much larger squalene (M(w) = 411) could be adsorbed from the liquid state, while several dyes were taken up from solutions in ether. Some dyes gave dichroic complexes, implying alignment of the chromophores in the NPSU channels. Notably, these complexes were formed by direct adsorption rather than cocrystallization, emphasizing the unusually robust nature of these organic molecular hosts.

Colorimetric N-butyl-3,6-diamidecarbazole-based chemosensors for detection of fluoride and cyanide anions.

Colorimetric sensors from N-butyl-3,6-disubstituted carbazole derivatives containing nitroazobenzene (1) and nitrobenzene (2) were designed, synthesized and compared for their anion sensing ability. Computational simulations were undertaken to determine the optimum geometry of 1. Anion sensing studies revealed that selectivity in anion detection depended on the polarity of solvent, acidity of binding unit and basicity of the anion. The ability to sense via naked eye observations using the strong basic anions (F- and CN-) for both sensors arises from a deprotonation process at the binding sites attributed to the intramolecular charge transfer transition at the sensory unit. The discrimination of F- from CN- has been achieved by the optimization of solvent polarity. Sensor 1 offers a promising property over sensor 2 with a lower detection limit, a few of anion interference and higher stability.

Crystal structure of bis-[µ-meth-oxy(pyridin-2-yl)methano-lato-κ(3) N,O:O]bis[chlorido-copper(II)].

The racemic title compound, [Cu2(C7H8NO2)2Cl2], is composed of dinuclear mol-ecules in which meth-oxy(pyridin-2-yl)methano-late ligands bridge two symmetry-related Cu(II) ions. Each Cu(II) ion is coordinated in a square-planar geometry by one Cl atom, the N and O atoms of the bidentate ligand and the bridging O atom of the centrosymmetrically related bidentate ligand. The separation between the two Cu(II) atoms is 3.005 (1) Å. In the crystal, non-classical C-H⋯O hydrogen bonds, weak π-π stacking [centroid-centroid distance = 4.073 (1) Å] and weak electrostatic Cu⋯Cl inter-actions [3.023 (1) Å] link the dinuclear mol-ecules into chains running parallel to the b axis. These chains are further connected by weak C-H⋯Cl hydrogen bonds directed approximately along the a axis, forming a three-dimensional supra-molecular network.