Organometallic complexes containing Ti, Al and Zn

Abstract

As new catalytic systems for lactide, trichlorotitanium and dichlorotitanium species containing chiral tridentate Schiff base ligand were achieved by changing the solvents. Single-crystal X-ray structure analyses revealed that chlorotitanium complexes are monomeric and octahedral. The chiral tridentate ligand occupies the meridional position of octahedral geometry. Although the chlorotitanium complexes contained no typical initiating groups such as alkoxides or amides, they proved to be effective catalysts for the controlled ring opening polymerization (ROP) of lactide (LA) as shown by the linearity of molecular weight versus [LA]/[Ti] ratio as well as very narrow PDI values. Aluminum aryloxide complexes having two 2-hydroxyphenyl benzotriazole ligands(HBTA) were synthesized as the catalyst of lactide. Though they showed no activity in the polymerization of lactide, they showed emission of sky blue region (475nm) with large emission area in PL spectrum. (A half width of peak is 150nm) Unexpected μ-oxo aluminum complex, {Al(HBTA)2}2O, was synthesized and characterized by X-ray crystallography. TGA analysis reveals {Al(HBTA)2}2O is extremely thermally stable product.(5% weight loss point is about 400oC) From molecular orbital calculation of Al(HBTA)2(OPh), transition of HOMO-1 → LUMO +1 is dominant in absorption and transition of LUMO → HOMO is dominant in emission. To verify this calculation, red-shifted aluminum phenoxide complex having two HBTA ligands containing chlorine atom in benzotriazole group was synthesized. This result is in good agreement with the molecular orbital calculation. As the coordination chemistry of academic purpose, dimeric or monomeric trichlorotitanium species containing 2-hydroxyphenyl benzotriazole ligand were achieved by changing the solvents. Single-crystal X-ray analysis revealed that chlorotitanium complex is dimeric in methylenechloride and monomeric in tetrahydrofuran. The 1H-NMR study suggested that coordination modes of tit...