Dissociation kinetics of the K(+) loss reaction of three potassiated tertiary amino acids (Scheme 1) were studied by infrared multiple photon dissociation (IRMPD) in a Fourier transform ion cyclotron resonance (FT ICR)-MS instrument. The aim of the study was to probe if a kinetic study by IRMPD can yield useful information on the ion structure of the precursor ion species. The measured activation energy values determined by IRMPD are related to the potassium affinity, DeltaH(K(+)), of N-methyl proline determined by threshold collision-induced dissociation experiments. By appropriate scaling with this reference value, the experimentally determined activation energy values for the K(+) loss are transformed into respective potassium affinities, DeltaH(K(+))(IRMPD). These values match the calculated potassium affinity values for salt bridge (SB) structures, DeltaH(K(+))(SB), substantially better than those for canonical structures with a single formal charge site (charge solvation (CS)), thereby allowing structure identification. This conclusion is consistent with other spectroscopic data, which yielded unambiguous evidence of these tertiary amino acids adopting SB structures in the gas phase. This study demonstrates that IRMPD can be applied to determine individual ion structures in the gas phase, given that adequate reference values are available for proper scaling.
Carbohydrates are interesting starting materials for scientific and industrial syntheses as they allow a versatile chemistry. Moreover, they are of natural origin and environmentally benign. During the past few years, inositol, a rather "exotic" carbohydrate, and its derivatives have gained increasing attention. Here, we describe the syntheses of new regiochemically defined inositol monoethers and monoesters as well as regioisomeric inositol ester mixtures and investigate their amphitropic liquid crystallinity. Furthermore, first results on their surface activity in aqueous solutions are given and compared with classical sugar surfactants.
Twenty new enantiopure chiral materials have been synthesized, showing liquid crystalline phases of smectic (SmA*), twisted grain boundary (TGB) and cholesteric (N*) type. The central ester-linkage as well as the length of the attached alkyl-chains were varied in a systematic way and the effects of these structural changes on the liquid crystalline properties have been studied. The liquid crystalline phases were characterized by means of differential scanning calorimetry, polarisation microscopy as well as small angle X-ray diffraction (SAXS).
Abstract In this article we describe research into the molecular design features for potential thermotropic biaxial nematogens of low-molar mass. We discuss how we can systematically change the shape of molecular structures in view of this aim of our work. The optical biaxialities of the materials prepared were tested through conoscopic and birefringence measurements. So far none of these materials synthesised and tested in this way have unequivocally exhibited the biaxial nematic phase. An overview of numerous further materials different in molecular shape and in part studied by others is also given. Key Words: Biaxial nematicsliquid crystalsgeometrical factorsmetal complexesmetallome-sogensmultifunctional compoundsradial multifacessynthetic routes
The synthesis of a homologous series of 5-(4-alkylphenyl)isatin derivatives, as well as the crystal structure and DFT studies of the respective hexyl derivative are presented, constituting the first examples of a new family of supramolecular bilayer forming isatin derivatives, which reveal a new type of molecular strand—a molecular arrangement also supported by quantum chemical calculations.
Abstract The chromophoric biheterocycle 2,5-dihydropyrrolo\[3,4-c]pyrrole-1,4-dione widely variable basic core structure has been introduced into liquid crystal research and the first eight calamitic examples of thermomesomorphic derivatives are presented and discussed. (DPPD) as a
Abstract Conoscopic studies reveal that the nematic phase of 4,4-(p-terphenyl)-bis\[2,3,4-tri(dodecyloxy)benzal]imine is biaxial, the biaxial angle increasing with schlieren textures exhibited by the nematic phase have been between glass plates, as well as free-standing consisting entirely of s or 2-brush disclinations, confirming an earlier suggestion that the absence of 4-brush disclinations is evidence of biaxiality. decreasing temperature. The examined. Films sandwiched films, exhibit a nematic schlieren texture
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