Department of Chemistry, Jawahar Navodaya Vidyalaya, Peddapuram-533 437, India Manuscript received 12 March 2003. revised 10 November 2003, accepted 18 February 2004 The electrochemical reduction behaviour of 3-(1-phenyl)-1-(2'-hydroxynaphthyl)-2-propen-1-one (PHPO) has been studied in aq. DMF media of pH 2.0 to 12.0 by d.c. polarography. Diffusion coefficient (D) of the electrode process has been calculated. The stability constants of \(UO_2^{2+}\), Cu2+, Zn2+, Co2+, Ni2+ and Mn2+ complexes of PHPO have been determined in 75% (v/v) dioxane-water, acetone-water and 2-ethoxyethanol-water mixture using the Bjcrrum-Calvin pH titration technique as developed by Irving and Rossottii. The stability constants are in fair agreement with Irving-Williams order. The results obtained are compared with electrochemical reduction behaviour of PHPO and also with the data available in the literature. Abnormal behaviour of the chelates was observed in acetone-water medium. The thermodynamic parameters such as free energy, enthalpy and entropy changes involved in complexation have been calculated.