56164-41-1Relevant academic research and scientific papers
Symmetrical and Nonsymmetrical Meso-Meso Directly Linked Hydroporphyrin Dyads: Synthesis and Photochemical Properties
Esemoto, Nopondo N.,Satraitis, Andrius,Wiratan, Linda,Ptaszek, Marcin
, p. 2977 - 2988 (2018/03/26)
A series of a rigid meso-meso directly linked chlorin-chlorin, chlorin-bacteriochlorin, and bacteriochlorin-bacteriochlorin dyads, including free bases as well as Zn(II), Pd(II), and Cu(II) complexes, has been synthesized, and their absorption, emission, singlet oxygen (1O2) photosensitization, and electronic properties have been examined. Marked bathochromic shifts of the long-wavelength Qy absorption band and increase in fluorescence quantum yields in dyads, in comparison to the corresponding monomers, are observed. Nonsymmetrical dyads (except bacteriochlorin-bacteriochlorin) show two distinctive Qy bands, corresponding to the absorption of each dyad component. A nearly quantitative S1-S1 energy transfer between hydroporphyrins in dyads, leading to an almost exclusive emission of hydroporphyrin with a lower S1 energy, has been determined. Several symmetrical and all nonsymmetrical dyads exhibit a significant reduction in fluorescence quantum yields in solvents of high dielectric constants; this is attributed to the photoinduced electron transfer. The complexation of one macrocycle by Cu(II) or Pd(II) enhances intersystem crossing in the adjacent, free base dyad component, which is manifested by a significant reduction in fluorescence and increase in quantum yield of 1O2 photosensitization.
PHOTOCHEMISTRY OF PYRIDINE N-OXIDES. TRAPPING OF AN INTERMEDIATE WITH AMINES
Albini, Angelo,Fasani, Elisa,Lohse, Christian
, p. 113 - 124 (2007/10/02)
The photochemistry of pyridine N-oxide (1a) and the corresponding 4-benzyl (1b), 4-phenyl (1c), and 2,6-dimethyl (1d) derivatives has been investigated or reinvestigated.Substrates 1a and 1b yield a small amount of the corresponding 2-acylpyrroles (5a,b) as the only isolable product, 1d yields 5d in moderate yield and 1c yields 5c in aprotic and the 2-pyridone 7c in protic solvents.In the presence of diethylamine isomeric 5-diethylaminopentadienenitriles (3,4) are obtained in moderate yield along with deoxygenated pyridines (6).Under this condition no 5 is formed, but the yield of 7 is unchanged.These reactions are most economically accunted for by admitting that nitrene 11 is formed as an intermediate and undergoes rearrangement to pyrroles 5 or polymerization to tars, or it can be trapped by amines (proton abstraction followed by nucleophilic substitution) to yield products 3 and 4.The lactams 7 arise directly from the N-oxide singlet excited state, which is also involved in the deoxygenation by amines.
Pyoluteorin Derivatives. II. Synthetic Approaches to Pyrrole Ring Substituted Pyoluteorins (1)
Cue, Berkeley W.,Chamberlain, Nancy
, p. 667 - 670 (2007/10/02)
A method for the regiospecific synthesis of 3-substituted 2-aroylpyrroles is described.These pyrroles, which are structurally related to the naturally occuring antibiotic pyoluteorin, are prepared by a Friedel-Crafts aroylation of 4-substituted pyrrole-3-carboxylic acid esters with 2,6-dimethoxybenzoyl chloride.The carboalkoxy group is then removed by hydrolysis and decarboxylation to produce isomerically pure 3-substituted-2-(2',6'-dimethoxybenzoyl)pyrroles (5 and 13).Conversion of these pyrroles into pyoluteorin-like coumpounds led to some unexpected products which arise from facile cleavage of the dihydroxybenzoyl portion of the molecules during chlorination.
