Resonance Raman characterization of the different forms of ground-state 8-substituted 7-hydroxyquinoline caged acetate compounds in aqueous solutions

Hui Ying An, Chensheng Ma, Wen Li, Kyle T. Harris, Timothy Dore, David Lee Phillips

Research output: Contribution to journalArticle

Abstract

To investigate the substituent effect on the distribution of the forms of the ground-state species of 8-substituted 7-hydroxyquinolines, ultraviolet-absorption and resonance Raman experiments were performed for 8-chloro7-hydroxyquinoline (CHQ-OAc) and 8-cyano-7-hydroxyquinoline (CyHQ-OAc) in acetonitrile (MeCN), in NaOH-H2O/MeCN (60:40, v/v, pH 11-12), and in H2O/MeCN (60:40, v/v, pH 6-7) solutions, and these results were compared to those previously reported for the 8-bromo-7-hydroxyquinoline (BHQ-OAc) compound. Swapping a bromine atom in BHQ-OAc for a chlorine atom in CHQ-OAc causes the amount of the tautomeric species to become larger, although the neutral species is still the predominant species for both systems in water-rich solutions. The absorption spectra and the resonance Raman spectra of CyHQ-OAc suggest that, because of the strong electron-withdrawing nature of the cyano substituent, a measurable amount of the anionic species is present and the tautomeric species cannot be easily detected in water-rich solutions. The results reported here reveal large substituent effects on the distribution of the different forms of the XHQ-OAc compounds in largely aqueous solutions. The steric effect of the 8-substituted group and competitive hydrogen bonding between the 8-substituted group and water molecules hinders the formation of a cyclic BHQ-OAc-water complex, and the electron-withdrawing property of the 8-substituted group enhances the deprotonation of the phenol group while disfavoring the formation of the positively charged quinoline nitrogen. We briefly discuss the implications of the substituent effects for using these compounds as phototriggers.

Original languageEnglish (US)
Pages (from-to)2498-2505
Number of pages8
JournalJournal of Physical Chemistry A
Volume114
Issue number7
DOIs
StatePublished - Feb 25 2010

Fingerprint

Ground state
acetates
Acetates
aqueous solutions
ground state
Water
water
Oxyquinoline
Bromine
Atoms
Deprotonation
Electrons
ultraviolet absorption
Chlorine
quinoline
bromine
Phenol
phenols
acetonitrile
chlorine

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Resonance Raman characterization of the different forms of ground-state 8-substituted 7-hydroxyquinoline caged acetate compounds in aqueous solutions. / An, Hui Ying; Ma, Chensheng; Li, Wen; Harris, Kyle T.; Dore, Timothy; Phillips, David Lee.

In: Journal of Physical Chemistry A, Vol. 114, No. 7, 25.02.2010, p. 2498-2505.

Research output: Contribution to journalArticle

@article{9dcb24857ff141d086afdc5a2675ce99,
title = "Resonance Raman characterization of the different forms of ground-state 8-substituted 7-hydroxyquinoline caged acetate compounds in aqueous solutions",
abstract = "To investigate the substituent effect on the distribution of the forms of the ground-state species of 8-substituted 7-hydroxyquinolines, ultraviolet-absorption and resonance Raman experiments were performed for 8-chloro7-hydroxyquinoline (CHQ-OAc) and 8-cyano-7-hydroxyquinoline (CyHQ-OAc) in acetonitrile (MeCN), in NaOH-H2O/MeCN (60:40, v/v, pH 11-12), and in H2O/MeCN (60:40, v/v, pH 6-7) solutions, and these results were compared to those previously reported for the 8-bromo-7-hydroxyquinoline (BHQ-OAc) compound. Swapping a bromine atom in BHQ-OAc for a chlorine atom in CHQ-OAc causes the amount of the tautomeric species to become larger, although the neutral species is still the predominant species for both systems in water-rich solutions. The absorption spectra and the resonance Raman spectra of CyHQ-OAc suggest that, because of the strong electron-withdrawing nature of the cyano substituent, a measurable amount of the anionic species is present and the tautomeric species cannot be easily detected in water-rich solutions. The results reported here reveal large substituent effects on the distribution of the different forms of the XHQ-OAc compounds in largely aqueous solutions. The steric effect of the 8-substituted group and competitive hydrogen bonding between the 8-substituted group and water molecules hinders the formation of a cyclic BHQ-OAc-water complex, and the electron-withdrawing property of the 8-substituted group enhances the deprotonation of the phenol group while disfavoring the formation of the positively charged quinoline nitrogen. We briefly discuss the implications of the substituent effects for using these compounds as phototriggers.",
author = "An, {Hui Ying} and Chensheng Ma and Wen Li and Harris, {Kyle T.} and Timothy Dore and Phillips, {David Lee}",
year = "2010",
month = "2",
day = "25",
doi = "10.1021/jp911143e",
language = "English (US)",
volume = "114",
pages = "2498--2505",
journal = "Journal of Physical Chemistry A",
issn = "1089-5639",
publisher = "American Chemical Society",
number = "7",

}

TY - JOUR

T1 - Resonance Raman characterization of the different forms of ground-state 8-substituted 7-hydroxyquinoline caged acetate compounds in aqueous solutions

AU - An, Hui Ying

AU - Ma, Chensheng

AU - Li, Wen

AU - Harris, Kyle T.

AU - Dore, Timothy

AU - Phillips, David Lee

PY - 2010/2/25

Y1 - 2010/2/25

N2 - To investigate the substituent effect on the distribution of the forms of the ground-state species of 8-substituted 7-hydroxyquinolines, ultraviolet-absorption and resonance Raman experiments were performed for 8-chloro7-hydroxyquinoline (CHQ-OAc) and 8-cyano-7-hydroxyquinoline (CyHQ-OAc) in acetonitrile (MeCN), in NaOH-H2O/MeCN (60:40, v/v, pH 11-12), and in H2O/MeCN (60:40, v/v, pH 6-7) solutions, and these results were compared to those previously reported for the 8-bromo-7-hydroxyquinoline (BHQ-OAc) compound. Swapping a bromine atom in BHQ-OAc for a chlorine atom in CHQ-OAc causes the amount of the tautomeric species to become larger, although the neutral species is still the predominant species for both systems in water-rich solutions. The absorption spectra and the resonance Raman spectra of CyHQ-OAc suggest that, because of the strong electron-withdrawing nature of the cyano substituent, a measurable amount of the anionic species is present and the tautomeric species cannot be easily detected in water-rich solutions. The results reported here reveal large substituent effects on the distribution of the different forms of the XHQ-OAc compounds in largely aqueous solutions. The steric effect of the 8-substituted group and competitive hydrogen bonding between the 8-substituted group and water molecules hinders the formation of a cyclic BHQ-OAc-water complex, and the electron-withdrawing property of the 8-substituted group enhances the deprotonation of the phenol group while disfavoring the formation of the positively charged quinoline nitrogen. We briefly discuss the implications of the substituent effects for using these compounds as phototriggers.

AB - To investigate the substituent effect on the distribution of the forms of the ground-state species of 8-substituted 7-hydroxyquinolines, ultraviolet-absorption and resonance Raman experiments were performed for 8-chloro7-hydroxyquinoline (CHQ-OAc) and 8-cyano-7-hydroxyquinoline (CyHQ-OAc) in acetonitrile (MeCN), in NaOH-H2O/MeCN (60:40, v/v, pH 11-12), and in H2O/MeCN (60:40, v/v, pH 6-7) solutions, and these results were compared to those previously reported for the 8-bromo-7-hydroxyquinoline (BHQ-OAc) compound. Swapping a bromine atom in BHQ-OAc for a chlorine atom in CHQ-OAc causes the amount of the tautomeric species to become larger, although the neutral species is still the predominant species for both systems in water-rich solutions. The absorption spectra and the resonance Raman spectra of CyHQ-OAc suggest that, because of the strong electron-withdrawing nature of the cyano substituent, a measurable amount of the anionic species is present and the tautomeric species cannot be easily detected in water-rich solutions. The results reported here reveal large substituent effects on the distribution of the different forms of the XHQ-OAc compounds in largely aqueous solutions. The steric effect of the 8-substituted group and competitive hydrogen bonding between the 8-substituted group and water molecules hinders the formation of a cyclic BHQ-OAc-water complex, and the electron-withdrawing property of the 8-substituted group enhances the deprotonation of the phenol group while disfavoring the formation of the positively charged quinoline nitrogen. We briefly discuss the implications of the substituent effects for using these compounds as phototriggers.

UR - http://www.scopus.com/inward/record.url?scp=77249166546&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77249166546&partnerID=8YFLogxK

U2 - 10.1021/jp911143e

DO - 10.1021/jp911143e

M3 - Article

C2 - 20113003

AN - SCOPUS:77249166546

VL - 114

SP - 2498

EP - 2505

JO - Journal of Physical Chemistry A

JF - Journal of Physical Chemistry A

SN - 1089-5639

IS - 7

ER -