The variability in expressed HM with respect to its protein and energy content is high. This variability persists after standard fortification, possibly resulting in under- or overnutrition. Because both over- and undernutrition confer risks in later development, individualized fortification optimizes protein and energy intake.
Tetraphenylpyrene has been selected as a discotic core to promote liquid‐crystalline fluorescent columns in view of its high fluorescence quantum yield in solution and ease of substitution by flexible lateral side chains. The synthesis and characterization of ten new derivatives of pyrene have been carried out; the pyrene core has been substituted at the 1,3,6,8‐positions by phenylene rings bearing alkoxy, ester, thioether, or tris(alkoxy)benzoate groups on the para position; the compounds have been characterized by mass spectrometry and 1H NMR and UV‐vis spectroscopies. In order to generate liquid‐crystalline phases, the nature, number, and size of the side chains as well as the degree of polarity around the tetraphenylpyrene core have been varied. However, the desired liquid‐crystalline behavior has not been observed. The supramolecular order together with the absorption and emission properties in solution and the solid state are discussed and compared to theoretical predictions. Quantum‐chemical calculations rationalize the high solid‐state fluorescence of a tetraphenylpyrene derivative for which the crystal structure has been determined.
A concept for highly ordered solid-state structures with bright fluorescence is proposed: liquid crystals based
on tetraethynylpyrene chromophores, where the rigid core is functionalized with flexible, promesogenic alkoxy
chains. The synthesis of this novel material is presented. The thermotropic properties are studied by means
of differential scanning calorimetry (DSC), cross-polarized optical microscopy (POM), and X-ray diffraction.
The mesogen possesses an enantiotropic Colh phase over a large temperature range before clearing. The
material is highly fluorescent in solution and, most remarkably, in the condensed state, with a broad, strongly
red shifted emission. Fluorescence quantum yields (ΦF) have been determined to be 70% in dichloromethane
solution and 62% in the solid state. Concentration- and temperature-dependent absorption and emission studies
as well as quantum-chemical calculations on isolated molecules and dimers are used to clarify the type of
intermolecular interactions present as well as their influence on the fluorescence quantum yield and spectral
properties of the material. The high luminescence efficiency in the solid state is ascribed to rotated
chromophores, leading to an optically allowed lowest optical transition.
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