Syntheses, structures and catalysis of tetranuclear zinc N-alkoxide ketoiminate complexes for ring-opening polymerization of rac-lactide

In Situ Assembled Polynuclear Zinc Oxo Clusters Using Modified Schiff Bases as Ligands

A series of different cores and nuclearity zinc metal clusters 1-5 have been synthesized using Zn(ClO4)2·6H2O, Schiff-base primary ligands, and dibenzoyl methane (DBM) or monoethanolamine (MEA) as co-ligand in a room-temperature reaction. The structure of the complexes is characterized using single-crystal X-ray diffraction. Among them, (1) [Zn(L1)(DBM)] is mononuclear; (2) [Zn4(L2)2(DBM)4], (3) [Zn4(L2)4(H2O)2(ClO4)2]·2CH2Cl2, and (4) [Zn4(L3)2(DBM)4] have a cubane core; and (5) [Zn4(L4)4(MEA)2(ClO4)2] has a ladderlike core structure. Compounds 1-5 have also been characterized using UV-vis absorption and emission spectroscopies. For an in-depth understanding of the absorption spectra of 1 and 3, density functional theory (DFT) calculations have been performed, which suggest that the transitions correspond to the π → π* intraligand charge transfer (ILCT) transitions.