Relative steric size of SCH(3), OCH(3), and CH(3) groups from circular dichroism measurements

The impact of cationic substituents in phenalen-1-one photosensitizers on antimicrobial photodynamic efficacy

SAGUA with its guanidinium moiety reaching an efficacy of ≥6log₁₀ steps of bacteria killing at 10 μM after irradiation with blue light (20 mW cm⁻²) for 60 s (1.2 J cm⁻²) without exhibiting dark toxicity.

Regulation of supramolecular chirality and morphology of the LB film of achiral barbituric acid by amphiphilic matrix molecules

Previously, we have found that an achiral barbituric acid (BA) derivative, 5-(4-(N-methyl-N-hexadecylaminobenzylidene))-2,4,6-(1H,3H)-pyrimidinetrione (BAC16), could form molecular assemblies showing supramolecular chirality through the organization at the air/water interface. To acquire more knowledge of the formation mechanism of such supramolecular assemblies, some achiral molecules, such as stearic acid (SA), octadecylamine (ODA), and an analogue of BA without an alkyl chain, were mixed into the BAC16 system. The effects of these matrix molecules on the supramolecular chirality and surface morphologies of Lanmuir-Blodgett (LB) films were investigated. It was observed that, at a low molar ratio of the matrix molecules (below 10%), the chirality of the BAC16 assemblies could be maintained with only a reduction in the intensity. When the matrix fraction was increased, the supramolecular chirality of the mixed films disappeared. The addition of the matrix molecules can greatly change the surface morphologies of the mixed films. When SA was mixed with BAC16, the spiral nanofibers of BAC16 were changed to long nanofibers. When ODA was mixed, the hydrolytic cleavage reaction of BAC16 took place at the air/water interface and disordered spirals were obtained. When the analogous BA derivate without an alkyl chain was mixed, the phase-separating morphology was observed. These changes in the chirality and surface morphologies indicated firmly that the supramolecular chirality of BAC16 films were formed due to the cooperative arrangement of the molecules. A certain amount of matrix molecules will destroy the cooperative arrangement and thus the chirality.

Supramolecular Assemblies of a Series of 2-Arylbenzimidazoles at the Air/Water Interface: In Situ Coordination, Surface Architecture and Supramolecular Chirality

The spreading behavior and supramolecular assemblies of some arylbenzimidazoles with 2-substituted aromatic groups such as phenyl, naphthyl, anthryl and pyrenyl on water surface and the subphase containing AgNO3 were investigated. It was observed that although these compounds lack long alkyl chains, they showed surface activity when spread from chloroform solution on water surface and formed the supramolecular assemblies. When AgNO3 was present in the subphase, a coordination between the imidazole group of the compounds and Ag(I) occurred in situ in the spreading film, which was verified by the surface pressure/area (pi-A) isotherms and UV/Vis absorption spectra. Both the spreading films from water and the aqueous AgNO3 subphase were transferred onto solid substrates and their surface morphologies as well as properties were characterized by AFM, UV/Vis absorption and CD spectra. Various surface morphologies such as nanoparticles, block domains and nanoutensils were observed depending on the substituted aromatic groups. Interestingly, although all of these compounds were achiral, supramolecular chirality was obtained for some of the arylbenzimidazole films assembled from either the water surface or the subphase containing AgNO3. It was revealed that chiral assemblies could be obtained from water surface for the benzimidazoles which have pyrenyl or alpha-naphthyl groups. For benzimidazole derivative with anthryl group, chiral assemblies could be obtained when spreading on the aqueous AgNO3 subphase. For the benzimidazoles with phenyl or beta-naphthyl groups, no chirality was obtained. It was suggested that both the overcrowded stacking of the aromatic groups and the cooperative arrangement of the molecules on water surface or aqueous AgNO3 subphase play a crucial role in forming the chiral supramolecular assemblies.