Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Jan 10;3(1):314-328.
doi: 10.1021/acsomega.7b01833. eCollection 2018 Jan 31.

Effect of Microheterogeneity of Different Aqueous Binary Mixtures on the Proton Transfer Dynamics of [2,2'-Bipyridyl]-3,3'-diol: A Femtosecond Fluorescence Upconversion Study

Rupam Dutta  1 , Arghajit Pyne  1 , Dipankar Mondal  1 , Nilmoni Sarkar  1
Affiliations

Effect of Microheterogeneity of Different Aqueous Binary Mixtures on the Proton Transfer Dynamics of [2,2'-Bipyridyl]-3,3'-diol: A Femtosecond Fluorescence Upconversion Study

Rupam Dutta et al. ACS Omega. .

Abstract

In this article, we have investigated the excited-state intramolecular double proton transfer dynamics of [2,2'-bipyridyl]-3,3'-diol, BP(OH)2, in three alcohol-water binary mixtures, namely, ethanol (EtOH)-water, n-propanol (PrOH)-water, tert-butyl alcohol (TBA)-water, and dimethyl sulfoxide (DMSO)-water utilizing the femtosecond fluorescence upconversion technique. We have found that in alcohol-water binary mixtures the proton transfer (PT) pathway of BP(OH)2 is sequential and the anomalous slowdown in PT dynamics is observed in mole fraction (χ) ranges χEtOH = 0.04-0.07, χEtOH = 0.23-0.28, χPrOH = 0.17-0.30, χTBA = 0.12-0.21, and χTBA = 0.40-0.46. Our study sheds light on the involvement of water network in the PT dynamics. Reduction in water accessibility due to the involvement of water molecules in cluster formation results in hindered PT dynamics, and this retardation is more for the TBA-water binary mixture compared to that for the other two mixtures. Additionally, we have found two anomalous regions for the DMSO-water binary mixture in ranges χDMSO = 0.12-0.16 and χDMSO = 0.26-0.34. However, most interestingly, beyond χDMSO = 0.40, we do not find any growth component in the femtosecond fluorescence upconversion trace, which may be due to the change in the PT mechanism from a sequential water-mediated pathway to a concerted intramolecular pathway.

PubMed Disclaimer

Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Structures of Different Tautomers of BP(OH)2 Involved in Two Different ESIDPT Pathways: Stepwise and Concerted
Figure 1
Figure 1
Absorption spectra of BP(OH)2 in (a) ethanol (EtOH)/water, (b) n-propanol (n-PrOH)/water, (c) TBA/water, and (d) DMSO/water binary mixtures varying the mole fractions of alcohol or DMSO.
Figure 2
Figure 2
Steady-state fluorescence spectra of BP(OH)2 (λex = 345 nm) in (a) EtOH/water, (b) n-PrOH/water, (c) TBA/water, and (d) DMSO/water binary mixtures varying the mole fractions of alcohol or DMSO.
Figure 3
Figure 3
Fluorescence quantum yield of BP(OH)2 in different binary mixtures at the excitation wavelength of 345 nm as a function of increasing mole fraction of alcohols for (a) EtOH/water, (b) n-PrOH/water, and (c) TBA/water and increasing mole fraction of DMSO for (d) DMSO/water.
Figure 4
Figure 4
Normalized fluorescence upconversion traces of BP(OH)2 (λex = 380 nm) in (a) EtOH/water, (b) n-PrOH/water, (c) TBA/water, and (d) DMSO/water binary mixtures at different mole fractions of alcohols or DMSO and the femtosecond fluorescence kinetics is taken at the respective emission maxima (ranging from 465 to 480 nm) for different mole fractions.
Figure 5
Figure 5
Change in the fast time scale (τfast) of fluorescence upconversion traces of BP(OH)2 (λex = 380 nm) as a function of varying mole fraction of alcohols or DMSO for (a) EtOH/water, (b) n-PrOH /water, (c) TBA/water, and (d) DMSO/water.
Scheme 2
Scheme 2. Two Possible Proton Transfer Pathways of BP(OH)2 in Water
Figure 6
Figure 6
Femtosecond fluorescence anisotropy decays of BP(OH)2 (λex = 380 nm) in (a) EtOH/water, (b) n-PrOH/water, (c) TBA/water, and (d) DMSO/water binary mixtures at different mole fractions of alcohols or DMSO and the femtosecond fluorescence kinetics is taken at the respective emission maxima (ranging from 465–480 nm) for different mole fractions.
Figure 7
Figure 7
Change in the average rotational time of BP(OH)2 (λex = 380 nm) as a function of varying shear viscosity of the TBA–water binary mixture.
See this image and copyright information in PMC

References

    1. Electron and Proton Transfer in Chemistry and Biology. In Studies in Physical and Theoretical Chemistry; Müller A., Ratajczak H., Junge W., Diemann E., Eds.; Series 78; Elsevier Science Publishers B.V.: Amsterdam, 1992.
    1. Demchenko A. P. Visualization and Sensing of Intermolecular Interactions with Two-Color Fluorescent Probes. FEBS Lett. 2006, 580, 2951–2957. 10.1016/j.febslet.2006.03.091. - DOI - PubMed
    1. Tang K.-C.; Chang M.-J.; Lin T.-Y.; Pan H.-A.; Fang T.-C.; Chen K.-Y.; Hung W.-Y.; Hsu Y.-H.; Chou P.-T. Fine Tuning the Energetics of Excited-State Intramolecular Proton Transfer (ESIPT): White Light Generation in A Single ESIPT System. J. Am. Chem. Soc. 2011, 133, 17738–17745. 10.1021/ja2062693. - DOI - PubMed
    1. Park S.; Kwon J. E.; Kim S. H.; Seo J.; Chung K.; Park S. Y.; Jang D. J.; Medina B. M.; Gierschner J.; Park S. Y. A White-Light-Emitting Molecule: Frustrated Energy Transfer between Constituent Emitting Centers. J. Am. Chem. Soc. 2009, 131, 14043–14049. 10.1021/ja902533f. - DOI - PubMed
    1. Liu B.; Wang J.; Zhang G.; Bai R.; Pang Y. Flavone-Based ESIPT Ratiometric Chemodosimeter for Detection of Cysteine in Living Cells. ACS Appl. Mater. Interfaces 2014, 6, 4402–4407. 10.1021/am500102s. - DOI - PMC - PubMed