Vesicle-mediated growth of tubular branches and centimeter-long microtubes from a single molecule

The mechanism by which small molecules assemble into microscale tubular structures in aqueous solution remains poorly understood, particularly when the initial building blocks are non-amphiphilic molecules and no surfactant is used. It is here shown how a subnanometric molecule, namely p-aminothiophenol (p-ATP), prepared in normal water with a small amount of ethanol, spontaneously assembles into a new class of nanovesicle. Due to Brownian motion, these nanostructures rapidly grow into micrometric vesicles and start budding to yield macroscale tubular branches with a remarkable growth rate of ∼20 μm s⁻¹. A real-time visualization by optical microscopy reveals that tubular growth proceeds by vesicle walk and fusion on the apex (growth cone) and sides of the branches and ultimately leads to the generation of centimeter-long microtubes. This unprecedented growth mechanism is triggered by a pH-activated proton switch and maintained by hydrogen bonding. The vesicle fusion-mediated synthesis suggests that functional microtubes with biological properties can be efficiently prepared with a mixture of appropriate diaminophenyl blocks and the desired macromolecule. The reversibility, timescale, and very high yield (90%) of this synthetic approach make it a valuable model for the investigation of hierarchical and structural transition between organized assemblies with different size scales and morphologies.

Highly brominated porphyrins: synthesis, structure and their properties

This article reports the first perbromination of β-pyrrole and meso-phenyl groups of the 5,10,15,20-tetrakis(3',5'-dimethoxyphenyl)porphinato copper(II) to generate highly brominated porphyrin, 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(2',6'-dibromo-3',5'-dimethoxyphenyl)-porphinato copper(II), CuT (3',5'- DMP ) PBr 16 complex. Its crystal structure exhibited unusual five-coordination geometry with saddle shaped conformation of the porphyrin core. H2T(3',5'- DMP ) PBr 16 and its metal complexes exhibited large anodic shift of oxidation potentials with marginal changes in reduction potentials relative to their corresponding octabromotetraphenylporphyrin, MTPPBr 8 derivatives. The enhanced electron deficiency of the ZnT (3',5'-DMP)PBr16 complex was probed by axial ligation of various Lewis bases with differing pK a values. The ZnT (3',5'-DMP)PBr16 complex exhibited decrease in equilibrium constants for the ligation of bases relative to sterically unhindered ZnTPPBr 8. This has been ascribed to the sterics induced by the bulky ortho-bromo phenyl substituents that prevents the facile binding of Lewis bases to the Zn (II)-center.