How the two factors of concentration and ultrasonic wave power affect on formation of kinetically or thermodynamically stable lead(II) complex nano-structures

Abstract

The reaction between quinoline-2-carboxylic acid (HQ) and lead(II) acetate trihydrate (Pb(OAc)2·3H2O) results in formation of kinetically stable and thermodynamically stable [Pb2(Q) 2(OAc)2]n (1) and [Pb(Q)2] n (2), respectively. Compound 1 (kinetically stable) was formed in aprotic solvent of acetonitrile and is stable in it. We evaluated the reaction between HQ and Pb(OAc)2·3H2O in two different ultrasonic baths and investigated the effect of initial reagents concentration on morphology and kind of resulting products. The resulting samples were characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Although these reactions were performed in acetonitrile, only in two samples compound 1 was synthesized. Thus in other four samples, the resulting products were compound 2. Indeed, ultrasonic waves with ultra-high energy could change the kinetically stable 1 to thermodynamically stable 2 in acetonitrile. With the highest 0.1 M concentration of initial precursors, only thermodynamically stable product (2) obtained in both of two ultrasonic baths. In lower concentrations of initial precursors (0.025 M and 0.05 M), the kind of resulting product attributed to the type of ultrasonic bath and its wave power and frequency. © 2014 Elsevier B.V. All rights reserved.