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In this paper we report the synthesis of 4,4'-bis(benzylideneamino)diphenyl ether (1), 4,4'-bis(p-methoxybenzylideneamino)diphenyl ether (2), 4,4'-bis(p-nitrobenzylideneamino)diphenyl ether (3), 4,4'-bis(benzylamino)diphenyl ether (4) and 4,4'-bis(p-methoxybenzylamino)diphenyl ether (5). The new compounds were characterized by using standard spectroscopic techniques. Supramolecular structures of 1-4 have been studied by using single-crystal X-ray diffraction to gauge the influence of substituents, present on para-positions of peripheral phenyl rings, on the association of molecules in the solid state. The study showed that introduction of p-OCH3 and p-NO2 substituents on peripheral phenyl rings, successfully switches off CH center dot center dot center dot pi synthons seen in compound 1 and 4 and that the new compounds adopt other packing strategies based on CH center dot center dot center dot O (2) and CH center dot center dot center dot N, CH center dot center dot center dot O and pi center dot center dot center dot pi (3) interactions. The optical band gaps (Eg), calculated by optical absorption method fall in the range of 2.16-3.0 eV and demonstrate a wide band gap semiconducting nature of these compounds. The thermogravimetric study of these compounds suggests the total destruction of the molecules up to 550 degrees C with a remaining mass of

The role of noncovalent interactions in carbohydrate recognition by aromatic amino acids has long been reported. To develop a molecular understanding of noncovalent interactions in the recognition process, we have examined a series of binary complexes between 3-methylindole (3-MeIn) and sugars. In particular, the geometries and binding affinities of 3-MeIn with alpha/beta-D-glucose, beta-D-galactose, alpha-D-mannose and alpha/beta-L-fucose are obtained using the MP2(full)/6-31G(d,p) and the M06/TZV2D//MP2/6-31G(d,p) level of theories. The conventional hydrogen bonding such as N-H center dot center dot center dot O and C-H center dot center dot center dot O as well as nonconventional O-H center dot center dot center dot pi and C-H center dot center dot center dot pi type of interactions is, in general, identified as responsible for the moderately strong interaction energies. Large variations in the position orientations of 3-MeIn with respect to saccharide are noticed, within the same sugar family, as well as across different sugar series. Furthermore, complexes with large differences in their geometries are recognized as capable of exhibiting very similar interaction energies, underscoring the significance of exhaustive conformation sampling, as carried out in the present study. These observations are readily attributed to the differences in the efficiency of the type of interactions enlisted above. The highest and lowest interaction energies, upon inclusion of 50% BSSE correction, are found to be -16.02 and -6.22 kcal mol(-1), respectively, for alpha-D-glucose (1a) and alpha-L-fucose (5j). While more number of prominent conventional hydrogen bonding contacts remains as a characteristic feature of the strongly bound complexes, the lower end of the interaction energy spectrum is dominated by multiple C-H center dot center dot center dot pi interactions. The complexes exhibiting as many as four C-H center dot center dot center dot pi contacts are identified in the case of alpha/beta-D-glucose, beta-D-galactose, and alpha/beta-L-fucose with an interaction energy hovering around 8 kcal mol(-1). The presence of effective C-H center dot center dot center dot pi interactions is found to be dependent on the saccharide configuration as well as the area of the apolar patch constituted by the C-H groups. The study offers a comprehensive set of binary complexes, across different saccharides, which serves as an illustration of the significance and ubiquitous nature of C-H center dot center dot center dot pi interactions in carbohydrate binding in saccharide-protein complexes.

The structures of the binary complexes between phenylacetylene and several tertiary amines viz., triethylamine, 1-ethylpiperidine, 1-ethylpiperazine, 1-azabicyclo[2.2.2]octane, and 1,4-diazabicyclo[2.2.2]octane were inferred using infrared-optical double resonance spectroscopy. The IR spectra in the acetylenic C-H stretching region clearly rule out the formation of electrostatic dominated C-H center dot center dot center dot N hydrogen bonded complexes. The IR spectra also point to the fact that all the five tertiary amines interact with the extended pi electron density of the phenylacetylene moiety, leading to the formation of multidentate C-H center dot center dot center dot pi hydrogen bonded complexes. Additionally a very weak electrostatic C-H center dot center dot center dot N hydrogen bond enhances the stability of the complex marginally. The multidentate C-H center dot center dot center dot pi hydrogen bonded complexes are stabilized by a substantial contribution from the dispersion energy.