Jin Shi Ma

Switch from intra- to intermolecular H-bonds by ultrasound: induced gelation and distinct nanoscale morphologies.

During cooling of the ( R)-N-Fmoc-Octylglycine (Fmoc-OG)/cyclohexane solution, gelation is observed exclusively when ultrasound is used as an external stimulus, while deposit is obtained without sonication. The xerogel consists of entangled fibrous network made by interconnected nanofibers, while the deposit comprises large numbers of unbranched nanowires. It is found that the Fmoc-OG molecules form bilayer structures in both the deposit and the gel. However, the ratio ( R) between the Fmoc-OG molecules in a stable intramolecular H-bonding conformation and those in a metastable intermolecular H-bonding conformation can be tuned by the ultrasound, R (deposit) > R (gel). The increased population of the intermolecular H-bonding Fmoc-OG molecules induced by the ultrasonication facilitates to the interconnection of nanofibers for the formation of the fibrous network, and therefore gelation. The alteration in the morphologies and properties of the obtained nanomaterials induced by the ultrasound wave demonstrates a potential method for smart controlling of the functions of nanomaterials from the molecular level.

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

Summary Molecules containing polarized NH fragments that behave as anion-binding motifs are widely used as receptors for recognition and sensing purposes in aprotic solvents. We present here a new example of a receptor, 3-amino-5-(4,5,6,7-tetrahydro-1H-indol-2-yl)isoxazole-4-carboxamide (receptor 1), which contains pyrrole, amide and amino subunits. This receptor shows both changes in its UV–vis absorption and fluorescence emission spectra upon the addition of F−, resulting in highly selectivity for fluoride detection over other anions, such as Cl−, Br−, I−, HSO4 −, H2PO4 − and AcO− in CH3CN. 1H NMR titration, time-dependent density functional theory (TDDFT) calculations and other experiments confirm that the sensing process is brought about by deprotonation of the pyrrole-NH in receptor 1.

Diphenylchlorin and diphenylbacteriochlorin : Synthesis, spectroscopy and photosensitising properties

Two new photosensitisers, diphenylchlorin and diphenylbacteriochlorin, were prepared from the reduction of 5,10-diphenylporphyrin. These dyes are characterised by strong light absorption in the red spectral region and afford high yields of photosensitised singlet oxygen, photosensitiser anion radicals, and superoxide anion radical, based on studies using EPR spectroscopy. Consequently, they are potential photosensitisers for photodynamic therapy.

AN EFFICIENT ONE-STEP CONVERSION OF BILIVERDINS TO 14-FORMYLTRIPYRRINONES

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Intramolecular aggregation and optical limiting properties of triazine-linked mono-, bis- and tris-phthalocyanines.

A series of triazine-linked mono-, bis- and tris-phthalocyanines are synthesized, intramolecular aggregation is found in bis- and tris-phthalocyanines via π-π stacking interaction. Theoretical and experimental studies reveal the formation of the intramolecular aggregation. The spectrographic, photophysical and nonlinear optical properties of these compounds are adjusted for the formation of the intramolecular aggregation. The bis-phthalocyanine dimer presents smaller fluorescence quantum yield, lower triplet formation yield and the triplet-minus-ground state extinction coefficient, which causes poorer optical limiting performance. It is interesting that the tris-phthalocyanine is composed of a mono-phthalocyanine part and a bis-phthalocyanine part, the optical limiting property of the tris-phthalocyanine is similar to that of mono-phthalocyanine.

Syntheses and crystal structures of CuII and AgI coordination complexes based on the hydrolysis of N-salicylidene-2-aminopyridine

A mononuclear salicylaldehydato copper(II) complex and an infinite 2-aminopyridyl silver(I) coordination polymer have been synthesised by the self-assembly reaction based on the metal-induced hydrolysis of N-salicylidene-2-aminopyridine. The latter chain-like polymer is novel and unavailable under usual reaction conditions. Additionally, an interesting 2D polymeric network is formed from the weak intermolecular interactions.