Synthesis and Crystal Structures of β -Diketonato Associated Aluminium Complexes as Potential Catalysts for the Ring-Opening Polymerization of ε-Caprolactone.

A couple of novel crystalline aluminium(III) derivatives containing tridentate Schiff base ligand (HL) and β-diketones (acetylacetone = acac, benzoylacetone = bnzac, dibenzoylmethane = dbnz) viz [Al(L)bnzac] [Al1], [Al(L)dnbz] [Al2] and [Al(L)acac] [Al3] were synthesized and characterized well using different spectroscopic techniques and elemental analysis. Single crystal X-ray diffraction (SCXRD) analysis of Al2 & Al3 exhibited hexacoordinated geometry around aluminium centre atom. The ring opening polymerization (ROP) of caprolactone (CL) was evaluated to determine the catalytic potential of the complexes Al1-Al3 in absence as well as in presence of benzyl alcohol. IEnd group study was performed using MALDI-TOF spectrometry and 1H NMR spectral analysis verified the existence of the -OBn group as an end group. First order kinetics were found in the monomer aligned with the activated monomer mechanism for the catalysts. Density functional theory (DFT) was carried out to optimize the geometries at B3LYP/LANL2DZ level.