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 language | English |
|---|---|
| Pages (from-to) | 323-333 |
| Number of pages | 11 |
| Journal | Journal of Physical Chemistry A |
| Volume | 119 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - 15 Jan 2015 |
| Externally published | Yes |
Fingerprint
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 journal › Article
}
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 -