Directed assembly of mesoscopic metallocycles with controllable size, chirality, and functionality based on the robust Pt-alkynyl linkage

This paper describes expeditious stepwise directed assembly of large homochiral metallocycles with up to 38 6,6'-bis(alkynyl)-1,1'-binaphthalene bridging ligands (L) and 38 trans-Pt(PEt3)(2) ([Pt]) centers and with cavities as large as 22 nm in diameter. These unprecedented mesoscopic metallocycles are synthesized by cyclization of different lengths of oligomeric building blocks, L-m[Pt](m+1)Cl-2 (m = 1, 2, 3, 5, 7, 11, 19, and 31) and [Pt](n)Ln+1H2 (n = 1, 2, 3, 4, 5, 6, 10, 18, and 30), and have been characterized by a variety of techniques, including H-1{P-31}, C-13 {H-1}, and P-31 {H-1} NMR spectroscopy, MALDI-TOF MS, elemental analysis, FT-IR, UV-vis, CD, size-exclusion chromatography, and diffusion-ordered NMR spectroscopy. The present synthetic methodology was also extended to the synthesis of non-homochiral metallocycles of very different topologies and macrocyclic structures with additional functional groups precisely placed at different positions. This work provides a general strategy for the construction of nanoscopic and mesoscopic functional supramolecular architectures of controllable size, chirality, and functionality that cannot be accessed from the existing synthetic approaches.