Non-aqueous synthesis of nano-sized aluminium(III) isopropoxide derivatives with 8-hydroxyquinoline and their sol-gel transformation to nano-sized δ-alumina

Non-aqueous reactions of aluminum isopropoxide with 8-hydroxyquinoline (Hq = HONH6C9) in 1:1, 1:2 and 1:3 molar ratios in anhydrous benzene yield complexes of the type [q(n)Al(OPri)(3-n)] {where n = 1 (1), n = 2 (2), n = 3 (3)}. Progress of the reactions were monitored by estimating liberated 2-propanol in benzene-2-propanol azeotrope by oxidimetric method. All the products were fluorescent green powders, sparingly soluble in CHCl3. They were characterized by elemental analysis, FT-IR and (H-1, C-13 and Al-27) NMR studies. The ESI mass spectral studies indicate dimeric nature for (1) and (2) and monomeric nature for the compound (3). The XRD spectra of (1-3) showed crystalline nature with the average particle size of 45, 32 and 27 nm respectively, as evaluated from Debye-Scherrer equation. The XRD spectrum of (3) also suggests the formation of beta-crystalline polymorphs of Alq(3). The SEM images appear to indicate granular morphology for (1) and formation of cylindrical shaped rods for (2) and (3). Sol-gel hydrolysis of (1), (2) or (3) in presence of a strong acid as well as of the precursor, Al(OPri)(3),without acid or base catalyst, followed by sintering at 950 A degrees C yielded tetragonal primitive phase of nano-sized delta-alumina in all the cases, as reflected by their powder X-ray diffraction pattern. The IR, SEM and EDX studies also support the formation of transition alumina.