Please use this identifier to cite or link to this item:
Title: Theoretical and experimental insights into the complexation of 8-hydroxyquinoline-5-sulfonate with divalent ions of Group 12 metals
Authors: Ramos, M. Luísa 
Justino, Licínia L. G. 
Branco, Adriana 
Fonseca, Sofia M. 
Burrows, Hugh D. 
Keywords: Group 12 metals; Sulfoxine; NMR; Complexation; Optical sensing; DFT
Issue Date: 22-Mar-2013
Publisher: Elsevier
Citation: RAMOS, M. Luísa [et. al] - Theoretical and experimental insights into the complexation of 8-hydroxyquinoline-5-sulfonate with divalent ions of Group 12 metals. "Polyhedron". ISSN 0277-5387. Vol. 52 (2013) p. 743-749
Serial title, monograph or event: Polyhedron
Volume: 52
Abstract: The complexation of 8-hydroxyquinoline-5-sulfonic acid with cadmium(II) and mercury(II) has been studied in aqueous solutions using UV/visible absorption, fluorescence and 1H NMR spectroscopy, accompanied by DFT calculations. Results are compared with the behavior of zinc(II) and show in all cases the dominant formation of a 1:2 (metal:ligand) complex. DFT calculations under PCM (water) conditions indicate a preference for hexacoordinated metal centers with two ligands and two water molecules. However, while the zinc(II) complex has a square bipyramidal geometry, with the two 8-HQS ligands and metal in the same plane and two coordinated water molecules mutually trans, with cadmium(II) and mercury(II), the isomers in which the water molecules are in the cis geometry are more stable. Changes in UV–Vis absorption, fluorescence spectra and fluorescence intensity are observed on complexation. Fluorescence quantum yields follow the order Zn/8-HQS < Cd/8-HQS > Hg/8-HQS. We believe two competing factors may be involved: an increase in fluorescence on going from Zn(II) to Cd(II) due to increased stability, and a decrease on going increasing atomic number of the metal ion due to the heavy atom effect which increases intersystem crossing. Triplet state quantum yields were measured for the Zn(II) and Cd(II) complexes, and the value for the cadmium(II) complex is higher, in agreement with the heavy atom effect. However, the sum of fluorescence and triplet quantum yields in these cases is less than unity. It is suggested that there is a competing non-radiative route for deactivation of the excited state through ligand or solvent exchange. This provides a ready explanation of increased fluorescence yields when metal/8-HQS complexes are immobilized in solid matrices.
ISSN: 0277-5387
DOI: 10.1016/j.poly.2012.07.074
Rights: openAccess
Appears in Collections:FCTUC Química - Artigos em Revistas Internacionais

Files in This Item:
File Description SizeFormat
Theoretical and experimental insights into the complexation.pdf859.26 kBAdobe PDFView/Open
Show full item record


checked on Feb 18, 2020

Citations 10

checked on Jan 2, 2022

Page view(s)

checked on Dec 22, 2021

Download(s) 50

checked on Dec 22, 2021

Google ScholarTM




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