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.