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meso-Aryl sapphyrins with heteroatoms; synthesis, characterization, spectral and electrochemical properties

meso-Aryl sapphyrins with heteroatoms; synthesis, characterization, spectral and electrochemical properties
meso-Aryl sapphyrins with heteroatoms; synthesis, characterization, spectral and electrochemical properties
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 18? tetraphenylporphyrin and a 26? 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 ?redox observed for 3d suggests significant reduction of the HOMO–LUMO energy gap consistent with the large red shift observed for the Soret band.
1364-5471
961-968
Srinivasan, Alagar
04842003-40d2-4215-adea-ce2b9fd540e3
Pushpan, Simi K.
76ac501a-77bc-4d51-82f6-4e4f0b8b1fe0
Kumar, Murugaeson Ravi
df681bb8-0d2a-431e-a0b9-896e8aaeff56
Mahajan, Sumeet
b131f40a-479e-4432-b662-19d60d4069e9
Chandrashekar, Tavarekere K.
bcb068c0-c575-4686-a3c9-c9b8e320e2fa
Roy, Raja
5c86771f-3c8f-4a91-9953-f46dfbae6a03
Ramamurthy, P.
240c04e3-bed8-4288-9e56-5b078612c0b6
Srinivasan, Alagar
04842003-40d2-4215-adea-ce2b9fd540e3
Pushpan, Simi K.
76ac501a-77bc-4d51-82f6-4e4f0b8b1fe0
Kumar, Murugaeson Ravi
df681bb8-0d2a-431e-a0b9-896e8aaeff56
Mahajan, Sumeet
b131f40a-479e-4432-b662-19d60d4069e9
Chandrashekar, Tavarekere K.
bcb068c0-c575-4686-a3c9-c9b8e320e2fa
Roy, Raja
5c86771f-3c8f-4a91-9953-f46dfbae6a03
Ramamurthy, P.
240c04e3-bed8-4288-9e56-5b078612c0b6

Srinivasan, Alagar, Pushpan, Simi K., Kumar, Murugaeson Ravi, Mahajan, Sumeet, Chandrashekar, Tavarekere K., Roy, Raja and Ramamurthy, P. (1999) meso-Aryl sapphyrins with heteroatoms; synthesis, characterization, spectral and electrochemical properties. Journal of the Chemical Society, Perkin Transactions 2, (5), 961-968. (doi:10.1039/A900137I).

Record type: Article

Abstract

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 18? tetraphenylporphyrin and a 26? 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 ?redox observed for 3d suggests significant reduction of the HOMO–LUMO energy gap consistent with the large red shift observed for the Soret band.

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More information

Published date: 1999
Organisations: Institute for Life Sciences, Molecular Diagnostics & Thereputics

Identifiers

Local EPrints ID: 346832
URI: http://eprints.soton.ac.uk/id/eprint/346832
ISSN: 1364-5471
PURE UUID: c3d349a9-2c79-4ab8-9726-c18591e4ba51
ORCID for Sumeet Mahajan: ORCID iD orcid.org/0000-0001-8923-6666

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Date deposited: 27 Feb 2013 11:50
Last modified: 09 Nov 2021 03:16

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Contributors

Author: Alagar Srinivasan
Author: Simi K. Pushpan
Author: Murugaeson Ravi Kumar
Author: Sumeet Mahajan ORCID iD
Author: Tavarekere K. Chandrashekar
Author: Raja Roy
Author: P. Ramamurthy

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