Solvent and pH effects on the fluorescence of 7-(Dimethylamino)-2- fluorenesulfonate

Kwanghee Koh Park, Joon Woo Park, Andrew Hamilton

Research output: Contribution to journalArticle

Abstract

A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2- fluorenesulfonate (2,7-DAFS), was prepared by a three-step reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular charge-transfer (ICT) to π∈→∈π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless single band with a large Stokes shift, whereas that of the acidic form, *( +HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *( +HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence occurs. The pKa *was estimated as -1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15∈ ∈25 times greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant advantages for a variety of applications.

Original languageEnglish (US)
Pages (from-to)361-369
Number of pages9
JournalJournal of Fluorescence
Volume17
Issue number4
DOIs
StatePublished - Jul 2007

Fingerprint

pH effects
Fluorescence
water
Naphthalenesulfonates
Values
Group
Deprotonation
Molecules
Protonation
Quantum yield
Electron transitions
Titration
Fluorescent Dyes
Ground state
Protons
Charge transfer
Quenching
Switches
Water

Keywords

  • Aminofluorene
  • Fluorescent probes
  • Intramolecular charge transfer
  • Proton-induced quenching
  • Prototropism
  • Solvatochromic shift

ASJC Scopus subject areas

  • Analytical Chemistry
  • Clinical Biochemistry

Cite this

Solvent and pH effects on the fluorescence of 7-(Dimethylamino)-2- fluorenesulfonate. / Park, Kwanghee Koh; Park, Joon Woo; Hamilton, Andrew.

In: Journal of Fluorescence, Vol. 17, No. 4, 07.2007, p. 361-369.

Research output: Contribution to journalArticle

@article{6c7d59449a054d37908466d79daf978c,
title = "Solvent and pH effects on the fluorescence of 7-(Dimethylamino)-2- fluorenesulfonate",
abstract = "A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2- fluorenesulfonate (2,7-DAFS), was prepared by a three-step reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular charge-transfer (ICT) to π∈→∈π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless single band with a large Stokes shift, whereas that of the acidic form, *( +HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *( +HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence occurs. The pKa *was estimated as -1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15∈ ∈25 times greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant advantages for a variety of applications.",
keywords = "Aminofluorene, Fluorescent probes, Intramolecular charge transfer, Proton-induced quenching, Prototropism, Solvatochromic shift",
author = "Park, {Kwanghee Koh} and Park, {Joon Woo} and Andrew Hamilton",
year = "2007",
month = "7",
doi = "10.1007/s10895-007-0193-1",
language = "English (US)",
volume = "17",
pages = "361--369",
journal = "Journal of Fluorescence",
issn = "1053-0509",
publisher = "Springer New York",
number = "4",

}

TY - JOUR

T1 - Solvent and pH effects on the fluorescence of 7-(Dimethylamino)-2- fluorenesulfonate

AU - Park, Kwanghee Koh

AU - Park, Joon Woo

AU - Hamilton, Andrew

PY - 2007/7

Y1 - 2007/7

N2 - A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2- fluorenesulfonate (2,7-DAFS), was prepared by a three-step reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular charge-transfer (ICT) to π∈→∈π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless single band with a large Stokes shift, whereas that of the acidic form, *( +HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *( +HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence occurs. The pKa *was estimated as -1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15∈ ∈25 times greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant advantages for a variety of applications.

AB - A novel water-soluble solvatochromic molecule, 7-(dimethylamino)-2- fluorenesulfonate (2,7-DAFS), was prepared by a three-step reaction from 2-nitrofluorene in good overall yield. The pH and solvent effects on the UV-VIS absorption and fluorescence spectra of 2,7-DAFS have been studied. Protonation of the dimethylamino group switches the absorption from intramolecular charge-transfer (ICT) to π∈→∈π* transition. The ground state pKa value of 2,7-DAFS was determined as 4.51. The fluorescence spectrum of the excited basic form, *(DAFS), shows a structureless single band with a large Stokes shift, whereas that of the acidic form, *( +HDAFS), exhibits a structured band with a small Stokes shift. The emission intensities of the basic and acidic forms versus pH/Ho plots show stretched sigmoidal curves and indicate that (1) the rate of deprotonation of *( +HDAFS) is comparable to the fluorescence decay of the species, and (2) the efficient proton-induced quenching of *(DAFS) fluorescence occurs. The pKa *was estimated as -1.7 from the fluorescence titration curve. The fluorescence maximum of *(DAFS) is blue-shifted as the polarity of solvent decreases. However, no clear dependency of the emission intensity and spectral half width, and thus fluorescence quantum yield, on the solvent polarity was revealed. It appears that the fluorescence sensitivity of 2,7-DAFS is 15∈ ∈25 times greater than the sensitivity of a widely utilized fluorescent probe, 5-(dimethylamino)-1-naphthalenesulfonate. This higher sensitivity, together with the ease of derivatization, would provide the fluorene-based fluorescent molecules significant advantages for a variety of applications.

KW - Aminofluorene

KW - Fluorescent probes

KW - Intramolecular charge transfer

KW - Proton-induced quenching

KW - Prototropism

KW - Solvatochromic shift

UR - http://www.scopus.com/inward/record.url?scp=34547275903&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=34547275903&partnerID=8YFLogxK

U2 - 10.1007/s10895-007-0193-1

DO - 10.1007/s10895-007-0193-1

M3 - Article

VL - 17

SP - 361

EP - 369

JO - Journal of Fluorescence

JF - Journal of Fluorescence

SN - 1053-0509

IS - 4

ER -