Acid-Base Strength and Acidochromism of Some Dimethylamino-Azinium Iodides. An Integrated Experimental and Theoretical Study

Enrico Benassi, Benedetta Carlotti, Cosimo G. Fortuna, Vincenzo Barone, Fausto Elisei, Anna Spalletti

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

The effects of pH on the spectral properties of stilbazolium salts bearing dimethylamino substituents, namely, trans isomers of the iodides of the dipolar E-[2-(4-dimethylamino)styryl]-1-methylpyridinium, its branched quadrupolar analogue E,E-[2,6-di-(p-dimethylamino)styryl]-1-methylpyridinium, and three analogues, chosen to investigate the effects of the stronger quinolinium acceptor, the longer butadiene π bridge, or both, were investigated through a joint experimental and computational approach. A noticeable acidochromism of the absorption spectra (interesting for applications) was observed, with the basic and protonated species giving intensely colored and transparent solutions, respectively. The acid-base equilibrium constants for the protonation of the dimethylamino group in the ground state (pKa) were experimentally derived. Theoretical calculations according to the thermodynamic Born-Haber cycle provided pKa values in good agreement with the experimental values. The very low fluorescence yield did not allow a direct investigation of the changes in the acid-base properties in the excited state (pKaa∗) by fluorimetric titrations. Their values were derived by quantum-mechanical calculations and estimated experimentally on the basis of the Förster cycle. (Figure Presented).

Original languageEnglish
Pages (from-to)323-333
Number of pages11
JournalJournal of Physical Chemistry A
Volume119
Issue number2
DOIs
Publication statusPublished - 15 Jan 2015
Externally publishedYes

Fingerprint

Iodides
iodides
Bearings (structural)
analogs
acid base equilibrium
cycles
acids
Acids
Protonation
Equilibrium constants
butadiene
Titration
Excited states
titration
Isomers
Ground state
Absorption spectra
isomers
Salts
Fluorescence

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Acid-Base Strength and Acidochromism of Some Dimethylamino-Azinium Iodides. An Integrated Experimental and Theoretical Study. / Benassi, Enrico; Carlotti, Benedetta; Fortuna, Cosimo G.; Barone, Vincenzo; Elisei, Fausto; Spalletti, Anna.

In: Journal of Physical Chemistry A, Vol. 119, No. 2, 15.01.2015, p. 323-333.

Research output: Contribution to journalArticle

Benassi, Enrico ; Carlotti, Benedetta ; Fortuna, Cosimo G. ; Barone, Vincenzo ; Elisei, Fausto ; Spalletti, Anna. / Acid-Base Strength and Acidochromism of Some Dimethylamino-Azinium Iodides. An Integrated Experimental and Theoretical Study. In: Journal of Physical Chemistry A. 2015 ; Vol. 119, No. 2. pp. 323-333.
@article{645f2b936ea84326bd7b4c2dc9ecae06,
title = "Acid-Base Strength and Acidochromism of Some Dimethylamino-Azinium Iodides. An Integrated Experimental and Theoretical Study",
abstract = "The effects of pH on the spectral properties of stilbazolium salts bearing dimethylamino substituents, namely, trans isomers of the iodides of the dipolar E-[2-(4-dimethylamino)styryl]-1-methylpyridinium, its branched quadrupolar analogue E,E-[2,6-di-(p-dimethylamino)styryl]-1-methylpyridinium, and three analogues, chosen to investigate the effects of the stronger quinolinium acceptor, the longer butadiene π bridge, or both, were investigated through a joint experimental and computational approach. A noticeable acidochromism of the absorption spectra (interesting for applications) was observed, with the basic and protonated species giving intensely colored and transparent solutions, respectively. The acid-base equilibrium constants for the protonation of the dimethylamino group in the ground state (pKa) were experimentally derived. Theoretical calculations according to the thermodynamic Born-Haber cycle provided pKa values in good agreement with the experimental values. The very low fluorescence yield did not allow a direct investigation of the changes in the acid-base properties in the excited state (pKaa∗) by fluorimetric titrations. Their values were derived by quantum-mechanical calculations and estimated experimentally on the basis of the F{\"o}rster cycle. (Figure Presented).",
author = "Enrico Benassi and Benedetta Carlotti and Fortuna, {Cosimo G.} and Vincenzo Barone and Fausto Elisei and Anna Spalletti",
year = "2015",
month = "1",
day = "15",
doi = "10.1021/jp510982h",
language = "English",
volume = "119",
pages = "323--333",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "2",

}

TY - JOUR

T1 - Acid-Base Strength and Acidochromism of Some Dimethylamino-Azinium Iodides. An Integrated Experimental and Theoretical Study

AU - Benassi, Enrico

AU - Carlotti, Benedetta

AU - Fortuna, Cosimo G.

AU - Barone, Vincenzo

AU - Elisei, Fausto

AU - Spalletti, Anna

PY - 2015/1/15

Y1 - 2015/1/15

N2 - The effects of pH on the spectral properties of stilbazolium salts bearing dimethylamino substituents, namely, trans isomers of the iodides of the dipolar E-[2-(4-dimethylamino)styryl]-1-methylpyridinium, its branched quadrupolar analogue E,E-[2,6-di-(p-dimethylamino)styryl]-1-methylpyridinium, and three analogues, chosen to investigate the effects of the stronger quinolinium acceptor, the longer butadiene π bridge, or both, were investigated through a joint experimental and computational approach. A noticeable acidochromism of the absorption spectra (interesting for applications) was observed, with the basic and protonated species giving intensely colored and transparent solutions, respectively. The acid-base equilibrium constants for the protonation of the dimethylamino group in the ground state (pKa) were experimentally derived. Theoretical calculations according to the thermodynamic Born-Haber cycle provided pKa values in good agreement with the experimental values. The very low fluorescence yield did not allow a direct investigation of the changes in the acid-base properties in the excited state (pKaa∗) by fluorimetric titrations. Their values were derived by quantum-mechanical calculations and estimated experimentally on the basis of the Förster cycle. (Figure Presented).

AB - The effects of pH on the spectral properties of stilbazolium salts bearing dimethylamino substituents, namely, trans isomers of the iodides of the dipolar E-[2-(4-dimethylamino)styryl]-1-methylpyridinium, its branched quadrupolar analogue E,E-[2,6-di-(p-dimethylamino)styryl]-1-methylpyridinium, and three analogues, chosen to investigate the effects of the stronger quinolinium acceptor, the longer butadiene π bridge, or both, were investigated through a joint experimental and computational approach. A noticeable acidochromism of the absorption spectra (interesting for applications) was observed, with the basic and protonated species giving intensely colored and transparent solutions, respectively. The acid-base equilibrium constants for the protonation of the dimethylamino group in the ground state (pKa) were experimentally derived. Theoretical calculations according to the thermodynamic Born-Haber cycle provided pKa values in good agreement with the experimental values. The very low fluorescence yield did not allow a direct investigation of the changes in the acid-base properties in the excited state (pKaa∗) by fluorimetric titrations. Their values were derived by quantum-mechanical calculations and estimated experimentally on the basis of the Förster cycle. (Figure Presented).

UR - http://www.scopus.com/inward/record.url?scp=84927523179&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84927523179&partnerID=8YFLogxK

U2 - 10.1021/jp510982h

DO - 10.1021/jp510982h

M3 - Article

VL - 119

SP - 323

EP - 333

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 2

ER -