Self-Assembly of a Pd₄Cu₈L₈ Cage for Epoxidation of Styrene and Its Derivatives

Abstract

Herein we report a discrete heterometallic Pd4Cu8L8 cage with a tubular structure, which was synthesized by the assembly of copper metalloligands and PdII ions in a stepwise manner. The Pd4Cu8L8 cage has been unequivocally characterized by single-crystal X-ray diffraction, electrospray ionization-mass spectroscopy, and energy dispersive spectroscopy. The cage showed excellent catalytic activity in the epoxidation of styrene and its derivatives under conditions without using additional solvent, providing potential material for catalyzing the oxidation reactions.

Experimental X-ray and DFT Structural Analyses of M12L8 Poly-[n]-catenanes Using exo-Tridentate Ligands

“…The self-assembly of discrete metal organic cages ( MOCs ) with well-defined voids is attracting much attention . Besides the exceptional symmetric structures, this finds functional applications in areas such as molecular separation, − catalysis, − and emergent behavior because of their internal nanoconfined space. ,− One strategy to combine the structural properties of MOCs and metal–organic frameworks ( MOFs ) − is by the preparation of poly-[ n ]-catenanes by mechanically interlocking metal organic cages − through mechanical bonds . − However, the synthesis of polycatenanes made of MOCs is not trivial because the cages need to have large windows where catenation can take place. − The self-assembly of Platonic icosahedral MOCs is elusive with very few examples reported so far. , Even more rare are the so-called one-dimensional (1D) M 12 L 8 poly-[ n ]-catenanes which are formed by the interlocking of M 12 L 8 nanocages in one crystallographic direction. This is because enthalpic and entropic aspects play a crucial role in the self-assembly of such large host guest systems. ,− Using exo-tridentate 2,4,6-tris-(4-pyridyl)­pyridine ( TPP ) , or 2,4,6-tris-(4-pyridyl)­benzene ( TPB ) ligands and ZnX 2 (where X = Cl and I), a new class of poly-[ n ]-catenanes self-assembled with large M 12 L 8 icosahedral nanocages have been synthesized in solution.…”

Heterometallic cages: synthesis and applications

“…24 Often for heterometallic cages, this first involves the formation of a relatively inert metallo-ligand complex before addition of the second more labile metal to complete the assembly of the cage structure. 59,104–114 Use of metallo-ligands in place of organic ligands potentially provides the resulting structures advantages such as new functionality, flexible geometric control and the ability to assemble many components into a discrete entity. 114 Exploiting the symmetry interaction approach outlined in Fig.…”

Hierarchical subcomponent self-assembly of covalent triple-stranded complexes with 3d–4f vertices: luminescence and magnetic properties

“…A myriad of diverse metallo-supramolecular compounds with sophisticated structures and fascinating functions, including, but not limited to, macrocycles, 10–12 helicates, 13–15 grids, 16,17 catenanes, 18 rotaxanes, 19 and metal–organic polyhedra, 20–23 have been successfully fabricated by the subcomponent self-assembly approach. Besides these types of structures, there is another type of structure composed of a discrete covalent organic skeleton and metal ions, namely discrete covalent metallo-supramolecular architectures, in which the metal ions are located at the vertices or panels of the covalent organic skeleton.…”

“…This type of structure is particularly appealing, since the introduction of metal ions not only can template the synthesis of covalent organic cages or covalent organic macrocycles 24–26 that cannot be acquired by traditional direct imine condensation, 27–32 but also endow the structure embedded by metal ions with special functions. 22,23,33–35 Therefore, templated metal ions play a dominant role in determining the structures and functions of discrete covalent metallo-supramolecular complexes. If two different metal ions, such as transition metal ions (3d) and lanthanide ions (4f), are simultaneously introduced into such systems, the intrinsic optical and large single-ion magnetic anisotropy of lanthanides together with remarkable magnetic interactions between 3d and 4f make such 3d–4f based complexes excellent candidates for luminescent materials and single molecular magnets (SMMs).…”