Corrole NH Tautomers: Spectral Features and Individual Protonation

Protonation of a free-base meso-pyrimidinyl-substituted AB2-corrole (H3AB2) in ethanol solution by stepwise addition of sulfuric acid has been studied in the temperature range from 293 to 333 K. The formation rate of protonated species was found to depend profoundly on the temperature at which the t...

Full description

Saved in:
Bibliographic Details
Published in:The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Molecules, spectroscopy, kinetics, environment, & general theory, 2012-11, Vol.116 (44), p.10683-10694
Main Authors: Ivanova, Yulia B, Savva, Vadim A, Mamardashvili, Nugzar Z, Starukhin, Aleksander S, Ngo, Thien H, Dehaen, Wim, Maes, Wouter, Kruk, Mikalai M
Format: Article
Language:English
Subjects:
Ethanol - chemistry
Ethyl alcohol
Fluid dynamics
Formations
Molecular Structure
Porphyrins - chemistry
Protonation
Protons
Solutions
Spectra
Spectrophotometry, Ultraviolet
Spectroscopy
Sulfuric Acids - chemistry
Tautomers
Temperature
Titration
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Protonation of a free-base meso-pyrimidinyl-substituted AB2-corrole (H3AB2) in ethanol solution by stepwise addition of sulfuric acid has been studied in the temperature range from 293 to 333 K. The formation rate of protonated species was found to depend profoundly on the temperature at which the titration was undertaken. Two steps in the titration curve were identified at temperatures around 293–298 K, whereas one-step formation of protonated species was found to occur at temperatures above 308 K. The protonation product was the same in both cases, i.e., H4AB2 + corrole, protonated at the macrocycle core nitrogen atoms. The two steps in the protonation kinetics at lower temperatures were attributed to protonation of individual tautomers of the free-base H3AB2 corrole. To the best of our knowledge, this is the first well-illustrated (spectrophotometric) observation of individual properties of corrole NH tautomers in fluid solution. Concomitant increase in the NH tautomerization rate with increasing temperature is proposed to account for the one-step protonation. Evidences for the role of individual corrole NH tautomers in the protonation process as well as their optical features are discussed based on spectroscopic results and simulation data.
ISSN:1089-5639
1520-5215
DOI:10.1021/jp305325e