30π Aromatic Meso-Substituted Heptaphyrin Isomers: Syntheses, Characterization, and Spectroscopic Studies
作者:Venkataramanarao G. Anand、Simi K. Pushpan、S. Venkatraman、Seenichamy Jeyaprakash Narayanan、Abhishek Dey、Tavarekere K. Chandrashekar、Raja Roy、Bhavani S. Joshi、S. Deepa、G. Narahari Sastry
DOI:10.1021/jo025788d
日期:2002.9.1
bithiophene unit or in the tripyrrane unit. Theoretical calculations performed on three different heptaphyrins, 4, 5, and 17, also reveal that the inverted structures are approximately 35-40 kJ lower in energy relative to the corresponding noninverted structures. Furthermore, one of the heptaphyrins 10c shows the presence of two conformers in solution in the ratio 1:2 and no interconversion between the conformers
Meso Aryl Heptaphyrins: The First 30π Aromatic Expanded Porphyrins with an Inverted Structure
作者:Venkataramana Rao. G. Anand、Simi K. Pushpan、Alagar Srinivasan、Seenichamy Jeyaprakash Narayanan、Bashyam Sridevi、Tavarekere K. Chandrashekar、Raja Roy、Bhavani S. Joshi
DOI:10.1021/ol000251c
日期:2000.11.1
[reaction: see text] Synthesis of new meso aryl 30pi heptaphyrins 2, 3, and 4 is achieved. Spectroscopic studies reveal that 2, 3, and 4 are aromatic and possess an inverted structure.
Novel Core-Modified Expanded Porphyrins with <i>meso</i>-Aryl Substituents: Synthesis, Spectral and Structural Characterization
作者:Seenichamy Jeyaprakash Narayanan、Bashyam Sridevi、Tavarekere K. Chandrashekar、Ashwani Vij、Raja Roy
DOI:10.1021/ja991472k
日期:1999.10.1
spectral and structural characterization of meso-aryl sapphyrins and rubyrins containing heteroatoms such as S, O, Se in addition to pyrrole nitrogens are reported. The synthesis of the desired expandedporphyrins has been achieved using a single precursor, the modified tripyrranes containing heteroatoms, through an unprecedented oxidative coupling reaction in moderately good yields. The product distribution
meso-Aryl sapphyrins with heteroatoms; synthesis, characterization, spectral and electrochemical properties
作者:Alagar Srinivasan、Simi K. Pushpan、Murugaeson Ravi Kumar、Sumeet Mahajan、Tavarekere K. Chandrashekar、Raja Roy、P. Ramamurthy
DOI:10.1039/a900137i
日期:——
The synthesis, characterization and spectral properties of six new meso-aryl core modified sapphyrins are described. An efficient approach involving an acid catalyzed condensation of bithiophene diol 1 and modified tripyrranes 2a–2e allows preparation of the desired meso-aryl sapphyrins in 16–36% yield. The product distribution and the isolated yield were found to be dependent on the nature of the acid catalyst (Lewis acid or protic acid) and its concentration. Protic acid catalyst exclusively gave the expected sapphyrins while two additional products, an 18π tetraphenylporphyrin and a 26π modified rubyrin, were isolated under Lewis acid catalysis. An analysis of proton NMR and absorption spectral data suggests that in free base sapphyrins, the heterocyclic ring opposite to the bithiophene unit is inverted as in N-5 meso-aryl sapphyrin and the degree of inversion is dependent on the nature of the heterocyclic ring. The energy optimized structure calculated from the semi-empirical method substantiates such a conclusion. Protonation of sapphyrins generates respective mono- and dications and the heterocyclic ring retains an inverted structure in contrast to normal N-5 sapphyrins. The triplet excited lifetimes for free base and protonated derivatives are similar both under argon saturated and air equilibrated conditions, indicating that the triplet state quenching by oxygen is minimal. Cyclic voltammetric studies reveal easier reductions and harder oxidations relative to meso-aryl porphyrins and the Δredox observed for 3d suggests significant reduction of the HOMO–LUMO energy gap consistent with the large red shift observed for the Soret band.
Characterization of a new meso-aryl rubyrin isomer: [26]hexaphyrin (1.1.1.0.1.0) with an inverted heterocyclic ring
作者:Simi, K Pushpan、Venkataramana Rao G Anand、Sundararaman Venkatraman、Alagar Srinivasan、Akhilesh K Gupta、Tavarekere K Chandrashekar
DOI:10.1016/s0040-4039(01)00451-8
日期:2001.5
The synthesis and characterization of new aromatic 26π macrocycles obtained from the acid catalyzed 4+3 coupling reaction of core modified tripyrrane and tetrapyrrane are described.