A general, direct, and high-yield synthesis of bis(salicylaldimine) zinc complexes from the ligands and Et(2)Zn is reported. This synthetic method is particularly valuable, not only because it allows the efficient preparation of salen-type complexes of zinc but also because it can be used to prepare bifunctional pyridine-modified zinc(II) bis(salicylidene) complexes, which are potentially useful compounds for applications in asymmetric catalysis and materials chemistry. The synthesis and complete structural characterization of a new series of pyridine-modified zinc(II) bis(salicylidene) ligands is discussed.

The absorption, emission, and energy-transfer properties of monomeric and supramolecular (salen)Zn complexes (square and rectangular assemblies) are reported. The monomeric complexes fluoresce in solution, displaying photophysical behavior similar to typical (porphyrin)zinc complexes. Rhenium coordination chemistry is used to assemble molecular rectangles and squares that largely retain the photophysical properties of the parent compounds. Host-guest assemblies

No abstract

Abstract(Salen)Mn(III) catalysts show increased turnover numbers in the catalytic asymmetric epoxidation of conjugated olefins upon addition of bulky Lewis acids (LA) such as zinc tetraphenylporphyrin (ZnTPP). Up to 3-fold increase in total catalytic activity and at least a 20-fold increase in catalyst stability was observed with a (salen)Mn catalyst bearing pendant 5,5 -bis-pyridyl groups. This latter enhancement is primarily attributed to formation of a coordination triad, which provides steric protection for the catalyst from bimolecular decomposition. Supramolecular complex formation enhanced the catalyst's stability without compromising its enantioselectivity.

Gel-permeation chromatography (GPC) has been used to analyze transition-metal-based squares, triangles, and related supramolecular complexes. Using rhenium-containing molecular squares of different sizes, a linear calibration curve has been established, which was used for confirming the relative sizes of other assemblies. GPC can also discriminate cyclic trimers and tetramers of a dirhodium building block. Preparative GPC has been used to resolve macroscopic samples of a rhenium-based supramolecular mixture into pure syn and anti isomers. A mixture of "triangle" and "square" has also been successfully separated.