Synthesis and characterization of some binuclear alkylene dithiophosphate complexes of bis(acetylacetonato)aluminium(III)-di-(μ-isopropoxo)di-isopropoxoaluminium(III) and sol-gel synthesis of nanosized θ-alumina

Abstract

Reactions of bis(acetylacetonato)aluminum(III)-di-(μ–isopropoxo)-di-isopropoxoaluminum(III) (A) with a variety of alkylenedithiophosphoric acids in different molar ratio yield products of the type [(CH3COCHCOCH3)2Al(μ-OPri)2Al{S(S)P(O-G-O)n(OPri)2-n] (1-9) {where G = C(CH3)2C(CH3)2, n=1[1], n=2[2]; -CH2CH(C2H5), n=1[3], n=2[4];CH2CH(CH3), n=1[5], n=2[6];C(CH3)2CH2CH(CH3), n=1[7]; CH(CH3)CH(CH3) n=1[8], n=2[9]}. Progress of the reaction is monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All pale coloured viscous products were soluble in common organic solvents and are characterized by elemental analyses, FT-IR and NMR (1H and 13C{1H} NMR) spectral studies. Molecular weight measurements in refluxing anhydrous benzene indicated binuclear nature of the complexes. 27Al NMR spectra of two of the derivatives, (1) and (2), suggested the presence of aluminium(III) atoms in different coordination states. 31P NMR spectra of the representative derivatives (1) and (2) exhibited only a single peak at 95.71 and 90.59 ppm, respectively, suggesting tetra-coordination around phosphorus atom and a bidentate mode of chelation of the dithio ligand. Sol-gel transformation of Al(OPri)3 and [(CH3COCHCOCH3)2Al(μ-OPri)2Al(OPri)2] (A) followed by sintering at ~850 °C yield alumina (a) and (b), respectively. The powder X-ray diffractionpatterns, SEM images and FT-IR spectral studies of (a) and (b) has indicated formation of nano-crystallites of θ -Al2O3 [PDF # 110517] in both the cases. The energy band gaps of 4.78 eV and 5.01 eV for (a) and (b), respectively are obtained from the absorption spectra.