Thangjam Promila Devi, Phanjoubam Pengkiliya, Lonibala Rajkumari
2014
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Journal
South African journal of chemistry
Abstract
Coordination behaviour of 3-hydroxypicolinamide (HPA) towards TbIII is studied in aqueous and micellar media. The complex formed exists asML2 species in which HPA behaves as anO,O,N,N-chelating ligand. The solid complex is isolated from aqueous medium and characterized employing elemental analysis, TG/DTA, magnetic, IR, ESR and mass spectral data. Stability constant and other accompanying thermodynamic parameters of the Tb III complex have been determined pHmetrically. The complexation reaction is spontaneous and exothermic. Effect of micelles andpHon the luminescence of Tb III were also studied. The emission peaks of Tb III are highly sensitized on complexation with HPA and the optimum luminescence efficiency is obtained in slightly acidic to neutral solutions (pH 6–8). The complex decays biexponentially and the presence of ethanol and surfactants causes a large increase in the luminescence intensity protecting the complex fromradiationless deactivation processes. KEYWORDS : 3-Hydroxypicolinamide, stability constant, micelles, terbium luminescence, sensitization.