8 research outputs found
Controlled Growth of Porphyrin Wires at a SolidâLiquid Interface
Bis(zinc porphyrin) scaffolds bearing C8 or C18 alkyl chains and imidazole end groups selfâassembled in a headâtoâtail fashion into multiâporphyrin assemblies on both HOPG and mica. Due to weaker molecule surfaceâinteractions, longer arrays formed on mica than on HOPG. In both cases, it was essential first to generate monomers that were drop casted on the surface, then to allow time for the bis(zinc porphyrins) to assemble. Although thicker fibrous assemblies were observed with the C8 alkyl substituents than with the longer chains, noncovalent assemblies up to 1â
ÎŒm long were observed for each molecule. These investigations provide a reproducible, noncovalent method to grow porphyrin arrays that may be of interest in molecular electronics for charge transport
Metal-mediated linear self-assembly of porphyrins
Porphyrin derivatives are highly relevant to biological processes such as light harvesting and charge separation. Their aromatic electronic structure and their accessible HOMOâLUMO gap render porphyrins highly attractive for the development of opto- and electro-active materials. Due to the often difficult covalent synthesis of multiporphyrins, self-assembly using metal complexation as the driving force can lead to well defined objects exhibiting a controlled morphology, which will be required to analyse and understand the electronic properties of porphyrin wires. This article presents two assembly approaches, namely by peripheral coordination or by binding to a metal ion in the porphyrin core, that are efficient and well designed for future developments requiring interactions with a surface
Peripherally Metalated Porphyrins with Applications in Catalysis, Molecular Electronics and Biomedicine
Pairing-up viologen cations and dications: a microscopic investigation of van der Waals interactions
Hydrogen bond directed molecular recognition in water in a strapped-porphyrin-cyclodextrin assembly
A water soluble, phenanthroline-strapped zinc porphyrin bearing four arylsulfonate groups formed a stable hostâguest complex with two per-O-methylated ÎČ-cyclodextrin cavities. In the hostâguest assembly, the zinc porphyrin was capable of binding imidazole within the cavity between the zinc(II) ion and the phenanthroline strap in an aqueous medium. The formation of a hydrogen bond between the imidazole NH and the nitrogen atoms of the phenanthroline was an essential element of the binding event, as shown by comparative binding studies with a non-strapped tetrasulfonated zinc porphyrin and with N-methylimidazole. This hydrogen bonding in an aqueous medium was possible due to the protected hydrophobic environment created by the cyclodextrins around the phenanthroline strap. This type of binding event may provide a biomimetic approach to study water soluble heme protein models
Probing the Growth of Organic Molecular Films Embedded between Cobalt and Iron Electrodes: Ferromagnetic Nuclear Resonance Approach
A water-soluble supramolecular complex that mimics the heme/copper hetero-binuclear site of cytochrome c oxidase
In mitochondria, cytochrome c oxidase (CcO) catalyses the reduction of oxygen (O2) to water by using a heme/copper hetero-binuclear active site. Here we report a highly efficient supramolecular approach for the construction of a water-soluble biomimetic model for the active site of CcO. A tridentate copper(II) complex was fixed onto 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(III) (FeIIITPPS) through supramolecular complexation between FeIIITPPS and a per-O-methylated ÎČ-cyclodextrin dimer linked by a (2,2âČ:6âČ,2âČâČ-terpyridyl)copper(II) complex (CuIITerpyCD2). The reduced FeIITPPS/CuITerpyCD2 complex reacted with O2 in an aqueous solution at pH 7 and 25 °C to form a superoxo-type FeIIIâO2â/CuI complex in a manner similar to CcO. The pH-dependent autoxidation of the O2 complex suggests that water molecules gathered at the distal Cu site are possibly involved in the FeIIIâO2â/CuI superoxo complex in an aqueous solution. Electrochemical analysis using a rotating disk electrode demonstrated the role of the FeTPPS/CuTerpyCD2 hetero-binuclear structure in the catalytic O2 reduction reaction