title: Improvement in Titanium Complexes Bearing Schiff Base Ligands in the Ring-Opening Polymerization of L-Lactide: A Dinuclear System with Hydrazine-Bridging Schiff Base Ligands.
abstract: A series of titanium (Ti) complexes bearing hydrazine-bridging Schiff base ligands were synthesized and investigated as catalysts for the ring-opening polymerization (ROP) of L-lactide (LA). Complexes with electron withdrawing or steric bulky groups reduced the catalytic activity. In addition, the steric bulky substituent on the imine groups reduced the space around the Ti atom and then reduced LA coordination with Ti atom, thereby reducing catalytic activity. All the dinuclear Ti complexes exhibited higher catalytic activity (approximately 10-60-fold) than mononuclear L(Cl-H)-TiOPr2 did. The strategy of bridging dinuclear Ti complexes with isopropoxide groups in the ROP of LA was successful, and adjusting the crowded heptacoordinated transition state by the bridging isopropoxide groups may be the key to our successful strategy.
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.
authors.forename: Hsi-Ching
authors.initials: HC
authors.lastname: Tseng
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.
authors.forename: Hsing-Yin
authors.initials: HY
authors.lastname: Chen
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.
authors.forename: Yen-Tzu
authors.initials: YT
authors.lastname: Huang
authors.affiliation: Department of Chemistry, National Chung Hsing University , Taichung 402, Taiwan R.O.C.
authors.forename: Wei-Yi
authors.initials: WY
authors.lastname: Lu
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.|Department of Chemistry, National Sun Yat-Sen University , Kaohsiung 804, Taiwan R.O.C.
authors.forename: Yu-Lun
authors.initials: YL
authors.lastname: Chang
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.|Department of Chemistry, National Sun Yat-Sen University , Kaohsiung 804, Taiwan R.O.C.
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Chiang
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Lai
authors.affiliation: Department of Medicinal and Applied Chemistry, Kaohsiung Medical University , Kaohsiung 80708, Taiwan R.O.C.
authors.forename: Hsuan-Ying
authors.initials: HY
authors.lastname: Chen