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

A family of neutral, heteroleptic, dinuclear MLL'-type pentagonal toroid-shaped metallomacrocycles () were synthesized using flexible ditopic N donors (L = L-L), rigid bis-chelating ligands (H-L' = H-E), and Re(CO) 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 , , , , and 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 , , , and as a model host with phenol and nitrobenzene derivatives as guest molecules were studied by emission spectroscopy methods.