Syntheses, Structures, and Solution Studies of Multicomponent Macrocycles and Cages Based on Versatile Ligands

5 years ago

Syntheses, Structures, and Solution Studies of Multicomponent Macrocycles and Cages Based on Versatile Ligands

Li-Wei Mi, Ying-Ying Zhang, Guo-Xin Jin, Yue-Jian Lin, Wen-Xi Gao

Different types of multinuclear half-sandwich rhodium macrocycles and cages were designed and synthesized by using two similar multifunctional hydroxamate ligands (pyrazine-2-hydroxamic acid (NaHL1) and 4,4′-bipyridine-2-hydroxamic acid (KHL2)) featuring one monodentate site and two pairs of chelating sites. The RhIII–PdII heterometallic macrocycles were constructed by using the semi-open palladium(II) source [Pd(en)Cl2] with two free acceptor sites. However, only one kind of macrocycle was found when the shorter ligand L1 was used, while in for the larger ligand, various spectroscopic techniques demonstrated the coexistence of hexanuclear and octanuclear macrocycles in solution and the proportions of both components depended on concentration and temperature. The palladium salt Pd(NO3)2, as a source of “naked” Pd2+, was introduced to assemble the cuboid-shaped cage composed of two types of metal ions and three types of organic ligands. In addition, two silver(I)-containing mixed-metal complexes bridged by pyrazine were obtained, in which two forms of decanuclear complex with C2v and C2h point symmetry cocrystallized—one is a polymeric structure and the other is a discrete cage. However, the third form, with D2 point symmetry, was found in the larger cage. Making metal sandwiches: Various types of multicomponent half-sandwich rhodium macrocycles and cages were selectively constructed utilizing two multifunctional hydroxamate ligands. An equilibrium between the hexanuclear and octanuclear macrocycles was investigated in solution, and molecules with different point symmetries were found in the Rh–Ag assemblies (see figure).

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201702244