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Organic fluorescent nanoparticles, excitation-dependent photoluminescence, hydrogen-bonded clusters and lysobisphosphatidic acid are four interesting individual topics in materials and biological sciences. They have attracted much attention not only because of their unique properties and important applications, but also because the nature of their intriguing phenomena remained unclear. Here we report a new type of organic fluorescent nanoparticles with intense blue and excitation-dependent visible fluorescence in the range of 410–620 nm. The nanoparticles are composed of ten bis(monoacylglycerol)bisphenol-A molecules and the self-assembly occurs only in elevated concentrations of 2-monoacylglycerol via radical-catalysed 3,2-acyl migration from 3-monoacylglycerol in neat conditions. The excitation-dependent fluorescence behaviour is caused by chromophores composed of hydrogen-bonded monoacylglycerol clusters, which are linked by an extensive hydrogen-bonding network between the ester carbonyl groups and the protons of the alcohols with collective proton motion and HO···C=O (n→π*) interactions.

The factors influencing the formation, organizations, and temperature ranges of the smectic phases of a structurally diverse family of phosphonium salts have been examined. The salts consist of one short group and three long n-alkyl chains attached to a positively charged phosphorus atom and either a free or covalently attached counterion, the latter resulting in zwitterionic salts. Of the 61 salts investigated, of which 37 have not been synthesized previously, most pack in lamellae within their solid phases. Single-crystal X-ray structures of two of amidomethyl-tri-n-tetradecylphosphonium bromide (1P14CONH(2)Br) and carboxymethyl-tri-n-tetradecylphosphonium bromide (1P14CO(2)HBr) have been solved. In each, the constituent molecules are packed in stacks of bilayers in which the directors of molecules on opposite sides of the ionic planes (where the phosphonium cationic centers and anions are located) that separate the layers are antiparallel. In each molecule, two of the long n-alkyl chains are paired while the third is antiparallel to the other two and paired with an n-alkyl chain of a molecule in a neighboring bilayer. The tri-n-alkylmethylphosphonium salts (1PnX) with small anions X (where n = 6-18 is the number of carbon atoms in the three long chain and 1 is the methyl group) do not form liquid-crystalline phases as a consequence of strong alternating intra- and intermolecular P(+)-X(-) interactions within the ionic planes that separate the bilayers of long chains. Thermotropic and enantiotropic liquid-crystalline phase formation of 1PnX salts is favored by larger anions and longer n-alkyl chains, which reduce order within ionic planes while promoting order within the lipophilic layers. We conjecture that covalent attachment of a hydroxymethylene, carboxy, or amido functional group Y to the alpha-methyl group of a 1PnX salt (resulting in mPnYX salts, where m is the number of methylene units separating the phosphorus atom from the Y group on the short chain) moves the anion X farther from the P(+) ion as a result of intramolecular X(-)...H(Y) H-bonding interactions and, therefore, substantially weakens intramolecular P(+)-X(-) ionic interactions within the ionic planes. In contrast to the trends mentioned for the 1PnX salts, liquid-crystalline phases of mPnYX are found more frequently when n is shorter and X is smaller. The observation that the liquid-crystalline phases of mPnYX salts have lower clearing and onset temperatures than the corresponding 1PnX may be attributed to the greater freedom of motion at and near the ionic planes of the former as a result of their more dispersed ionic interactions. Overall, a detailed study of the dependence of phase type and phase transition temperatures on several key structural factors of phosphonium salts has been made. The correlations found provide insights into how new mesmorphic phosphonium salts can be designed and exploited for a wide range of potential applications.

Liquid crystalline 1-acetamido-3-alkylimidazolium bromide, hexafluorophosphate and tetrafluoroborate salts with 3-alkyl chains of carbon number n ~10, 12, 14, 16 and 18 were prepared. The single crystal structure of the PF 6 2 salt of n ~12 self-organizes to form a framework of a hydrogen bonded ribbon polymer. The mesomorphic behaviors of these compounds were studied by polarized optical microscopy, differential scanning calorimetry and powder X-ray diffraction. The presence of extended hydrogen bonding interactions in these acetamidoimidazolium salts allows them to have a wide temperature range of the mesophase. Anions have a profound effect on the phase transition temperature, suggesting that both ionic and hydrogen bonding interactions play dominant roles in the mesomorphic behavior of these liquid crystalline compounds. {Electronic supplementary information (ESI) available: IR, proton and carbon NMR data for all compounds. See http://www.rsc.org/ suppdata/jm/b2/b210562d/ Scheme 1 Schematic representation of [C n , amide-im]X.Scheme 2 Hydrogen bonding motifs in primary amides.

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