Search results for "Free base"
showing 10 items of 27 documents
Theoretical study of the NH tautomerism in free base porphyrin
1997
Abstract The NH tautomerism of free base porphyrin is investigated at the semiempirical spin-unrestricted AM1 (UAM1) and ab initio RHF/3-21G levels. The UAM1 method provides delocalized geometries for all stationary structures without imposing any symmetry constraint. RHF/3-21G geometry optimizations have to be performed under symmetry restrictions to ensure that realistic delocalized structures are obtained. Both the semiempirical and the ab initio calculations predict that the interconversion between trans tautomers proceeds in an asynchronous two-step process via intermediate cis tautomers. The cis tautomers are characterized as minima in the potential energy surface and are 8–10 kcal m…
Electrochemistry, spectroelectrochemistry, chloride binding, and O2 catalytic reactions of free-base porphyrin-cobalt corrole dyads.
2005
Three face-to-face linked porphyrin-corrole dyads were investigated as to their electrochemistry, spectroelectrochemistry, and chloride-binding properties in dichloromethane or benzonitrile. The same three compounds were also investigated as to their ability to catalyze the electroreduction of dioxygen in aqueous 1 M HClO4 or HCl when adsorbed on a graphite electrode. The characterized compounds are represented as (PCY)H2Co, where P = a porphyrin dianion; C = a corrole trianion; and Y = a biphenylenyl, 9,9-dimethylxanthenyl, or anthracenyl spacer, which links the two macrocycles in a face-to-face arrangement. An axial binding of one or two Cl- ligands to the cobalt center of the corrole is …
Non-Innocent Base Properties of 3- and 4-Pyridyl-dithia- and Diselenadiazolyl Radicals : The Effect of N-Methylation
2018
International audience; Condensation of persilylated nicotinimideamide and isonicotinimideamide with sulfur monochloride affords double salts of the 3-, 4-pyridyl-substituted 1,2,3,5-dithiadiazolylium DTDA cations of the general formula [3-, 4-pyDTDA][Cl][HCl] in which the pyridyl nitrogen serves as a noninnocent base. Reduction of these salts with triphenylantimony followed by deprotonation of the intermediate-protonated radical affords the free base radicals [3-, 4-pyDTDA], the crystal structures of which, along with those of their diselenadiazolyl analogues [3-, 4-pyDSDA], have been characterized by powder or single-crystal X-ray diffraction. The crystal structures consist of “pancake” π…
Spectroscopic study of the loading of cationic porphyrins by carbon nanohorns as high capacity carriers of photoactive molecules to cells
2019
Carbon nanomaterials are attractive candidates for drug delivery due to their high surface area, ease of functionalisation and biocompatibility. This work describes the spectroscopic monitoring of the loading capacity of oxidised carbon nanohorns for two cationic porphyrins. Addition of the COOH functionalised carbon nanohorns to both meso-tetra(4-N-methylpyridyl) free base (H2TMPyP4) and platinum (PtTMPyP4) porphyrin in aqueous solution results in hypochromism of the Soret band and quenching of the porphyrin emission. These changes are used to monitor the non-covalent binding interactions with the nanohorn surface and determine the surface loading. The colloidal stability of the nanohorns …
Strong donor–acceptor couplings in a special pair-antenna model
2010
A special pair model composed of two cofacial zinc porphyrins (acceptor) linked to a free base (donor) acts as an energy transfer dyad. Despite the absence of conjugation, ππ*/charge transfer excited states and ultrafast energy transfer (∼5 ps) are noted.
Mono- and Tripodal Porphyrins: Investigation on the Influence of the Number of Pyrene Anchors in Carbon Nanotube and Graphene Hybrids.
2020
A series of molecular precursors, containing one (1 and 3) or three (2 and 4) pyrene anchors, covalently linked to porphyrins (free base or Zn), were prepared and characterized. All of them enable ...
The photophysics and photochemistry of cofacial free base and metallated bisporphyrins held together by covalent architectures
2007
Abstract This review focuses on the photophysical properties of bisporphyrin systems held in a face-to-face configuration by covalent bonds via flexible or rigid spacers and metal–metal bonds. The cofacial arrangement induces intramolecular bismacrocycle interactions promoting basic photophysical events such as excitonic interactions and energy and electron transfers. These events are relevant to mimic light harvesting and reactor devices known for photosynthesis in plants, and can be monitored by luminescence and flash photolysis methods.
New route to a face-to-face biscorrole free-base and the corresponding heterobimetallic copper(III)-silver(III) complex.
2004
A meso-aryl-substituted face-to-face biscorrole was synthesised in a two-step reaction and the corresponding homo- and heterobimetallic complexes were obtained and fully characterised.
Exploring the co-loading of lidocaine chemical forms in surfactant/phospholipid vesicles for improved skin delivery
2015
Abstract Objectives The present study was aimed at targeting the skin to deliver lidocaine loaded in surfactant/phospholipid vesicles tailored for improved local delivery. The influence of different formulation parameters was explored to maximise drug efficacy. Methods The vesicles were prepared using a mixture of soy lipids (Phospholipon 50) and a surfactant with penetration-enhancing properties (Oramix CG110, Labrasol, Labrafac PG or Labrafac CC), and loaded with lidocaine. The formulations were analysed in detail by cryo-TEM, SAXS, Turbiscan Lab, and tested in permeation experiments through new born pig skin, as a function of the chemical form and concentration of lidocaine (i.e. free ba…
A Functionalized Noncovalent Macrocyclic Multiporphyrin Assembly from a Dizinc(II) Bis-Porphyrin Receptor and a Free-Base Dipyridylporphyrin
2003
The bis-porphyrin system ZnP 2 , in which two zinc porphyrins are connected by a phenanthroline linker in an oblique fashion, acts as a bifunctional receptor towards the complexation of free-base meso-5,10-bis(4'-pyridyl)-15,20-diphenylporphyrin (4'-cisDPyP). In solution, NMR spectroscopy evidenced quantitative formation of the tris-porphyrin macrocyclic assembly ZnP 2 (4'-cisDPyP), in which the two fragments are held together by two axial 4'-N(pyridyl)-Zn interactions. The remarkable stability of the edifice (an association constant of about 6 x 10 8 M - 1 was determined by UV/Vis absorption and emission titration experiments in toluene) is due to the almost perfect geometrical match betwe…