Synthesis and guest recognition of molecular cleft consisting of terpyridine–Pt(II) acetylide complexes

The stable molecular clefts 1 consisting of inert Pt–acetylide moieties and a 1,1′:3′,1″-terphenyl spacer were synthesized. Guest binding behavior of 1a was examined by 1H NMR spectroscopy to determine the association constants; naphthalene (Ka ∼0 M–1) < anthracene (10 M–1) < pyrene (50 M–1) < coronene (640 M–1) in chloroform-d/acetonitrile-d3 (3:1, v/v). 1a is stable enough to resist disassembly in the presence of anionic species. Thus, 1a shows a higher affinity to large electron-rich aromatic compounds. In addition, anionic aromatic guests were bound more strongly by 1a (Ka = 540 M–1 for 1-pyrenecarboxylate) due to the electrostatic interactions, π–π interactions, and the stable cleft scaffold.