Synthesis and Characterization of Nanometric Pure Phase SnO₂ Obtained from Pyrolysis of Diorganotin(IV) Derivatives of Macrocycles

Abstract

Thermal decomposition of diorganotin(IV) derivatives of macrocycles of general formula, R 2 Sn(L1) and R 2 Sn(L2) (where R = n-butyl (1/4), methyl (2/5), and phenyl (3/6); H 2 L1 = 5,12-dioxa-7,14-dimethyl-1,4,8,11-tetraazacyclotetradeca-1,8-diene and H 2 L2 = 6,14-dioxa-8, 16-dimethyl-1,5,9,13-tetraazacyclotetradeca-1,9-diene), provides a simple route to prepare nanometric SnO 2 particles. X-ray line broadening shows that the particle size varies in the range of 36-57 nm. The particle size of SnO 2 obtained by pyrolysis of 3 and 5 is in the range of ∼5-20 nm as determined by transmission electron microscope (TEM). The surface morphology of SnO 2 particles was determined by scanning electron microscopy (SEM). Mathematical analysis of thermogravimetric analysis (TGA) data shows that the first step of decomposition of compound 4 follows first-order kinetics. The energy of activation (E * ), preexponential factor (A), entropy of activation (S * ), free energy of activation (G * ), and enthalpy of activation (H * ) of the first step of decomposition have also been calculated. Me 2 Sn(L2) and Ph 2 Sn(L1) are the best precursors among the studied diorganotin(IV) derivatives of macrocycles for the production of nanometric SnO 2 .