Rhenium(I)-Based Heteroleptic Pentagonal Toroid-Shaped Metallocavitands: Self-Assembly and Molecular Recognition Studies.

A family of neutral, heteroleptic, dinuclear M 2 LL'-type pentagonal toroid-shaped metallomacrocycles ( 1-8 ) were synthesized using flexible ditopic N donors (L n = L 1 -L 2 ), rigid bis-chelating ligands (H 2 -L' = H 2 -E), and Re 2 (CO) 10 in a one-pot solvothermal self-assembly approach. The ligands and the metallomacrocycles were characterized using ATR-IR, electrospray ionization mass spectrometry, nuclear magnetic resonance, ultraviolet-visible, and emission spectroscopy methods. The molecular structures of 1 , 2 , 4 , 6 , and 7 were confirmed by an X-ray diffraction study and are similar to those of calix[5]arene. The cyclic inner cavities of the metallomacrocycles accommodate toluene/mesitylene/acetone/chlorobenzene as guest molecules that are stabilized by cumulative C-H···π and π···π interactions with the cyclic framework of metallomacrocycle. The photophysical properties of the ligands and the metallomacrocycles were studied. The host-guest recognition properties of metallocavitands 1 , 2 , 7 , and 8 as a model host with phenol and nitrobenzene derivatives as guest molecules were studied by emission spectroscopy methods.