Please use this identifier to cite or link to this item: http://hdl.handle.net/10316/10331
Title: β-Carbolines. 2. Rate Constants of Proton Transfer from Multiexponential Decays in the Lowest Singlet Excited State of Harmine in Water As a Function of pH
Authors: Dias, A. 
Varela, A. P. 
Miguel, M. da Graça 
Becker, R. S. 
Burrows, H. D. 
Maçanita, A. L. 
Issue Date: 7-Nov-1996
Publisher: American Chemical Society
Citation: The Journal of Physical Chemistry. 100:45 (1996) 17970-17977
Abstract: The β-carbolines present a complex problem involving multiple equilibria in the excited state in hydrogen-bonding solvents including water. Three excited state species exist: neutral, cation, and zwitterion. Here we examine the multiple equilibria and excited state kinetics of harmine, using time-resolved and steady state fluorescence techniques. From an analysis of the multiexponential decays, measured at the emission wavelengths of the three species as a function of the pH, seven unknowns (four rate constants and three reciprocal lifetimes) were determined. Data analysis was made both by a previously reported numerical method and by analytical solution of the differential equation set. The results obtained accurately describe the independently obtained steady-state fluorescence results. The dramatic modifications of the equilibria and rate constants between the ground and excited states can be understood on the basis of the significative changes in charge densities on the two nitrogen atoms of harmine upon excitation. Mechanisms are proposed for the formation of excited state cation and zwitterion beginning with the excited state neutral molecule.
URI: http://hdl.handle.net/10316/10331
DOI: 10.1021/jp961406u
Rights: openAccess
Appears in Collections:FCTUC Química - Artigos em Revistas Internacionais

Files in This Item:
File Description SizeFormat
β-Carbolines. 2. Rate Constants of Proton Transfer.pdf907.73 kBAdobe PDFView/Open
Show full item record

SCOPUSTM   
Citations

44
checked on Nov 8, 2019

Page view(s)

86
checked on Nov 20, 2019

Download(s)

67
checked on Nov 20, 2019

Google ScholarTM

Check

Altmetric

Dimensions


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.