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Excited state intramolecular proton transfer (ESIPT) in a dioxotetraamine derived schiff base and its complexation with Fe(III) and Cr(III)

Paper ID Volume ID Publish Year Pages File Format Full-Text
28410 44074 2007 13 PDF Available
Title
Excited state intramolecular proton transfer (ESIPT) in a dioxotetraamine derived schiff base and its complexation with Fe(III) and Cr(III)
Abstract

The excited state intramolecular proton transfer (ESIPT) process in a symmetric Schiff base derived from dioxotetraamine and salicylaldehyde, N,N′-Bis{2-[(2-hydroxybenzylidine)amino]ethyl}malonamide (BHAEM) has been investigated experimentally by the fluorescent method and a two step proton transfer mechanism from dienol to ketoenol and then to diketo tautomer has been proposed on the basis of the theoretical evidence obtained through semi-empirical MO/CI calculations using the AM1 Hamiltonian. BHAEM on interaction with Fe(III) and Cr(III), in an aqueous medium of 0.1N ionic strength and 25 ± 1 °C forms monomeric metal complexes of the type ML and MLH−2 with both metal ions, whereas with Cr(III) it forms two more additional species, MLH and MLH−1. The stabilities of these metal complexes have been evaluated using potentiometric and spectrophotometric methods and the relative stabilities of the complexes formed with this ligand are rationalized. At low pH, the ligand coordinates to the metal ions through bis-imine nitrogen and bis-phenolate oxygen atoms but with an increase of pH, further coordination occurs through two amide nitrogen atoms of the ionized amide groups. The structures of the metal complexes were predicted from minimum strain energy calculations employing molecular mechanics using the MM3 force field and from their theoretical electronic spectra obtained through semi-empirical AM1/ZINDO method.

Keywords
ESIPT; Schiff base; Potential energy surface (PES); Transition state search; Stability constants; Molecular mechanics; Semi-empirical method
First Page Preview
Excited state intramolecular proton transfer (ESIPT) in a dioxotetraamine derived schiff base and its complexation with Fe(III) and Cr(III)
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 188, Issues 2–3, 20 May 2007, Pages 298–310
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering