Spheroid Metallacycles and Metallocavitands with Calixarene- and/or Cleft-Shaped Receptors on the Surface

Flexible hexatopic ligands, 1,2,3,4,5,6-hexakis­(1H-naphtho­[2,3-d]­imidazol-1-ylmethyl)­benzene (L²) and 1,2,3,4,5,6-hexakis­(4,5-diphenylimidazol-1-ylmethyl)­benzene (L³), containing six neutral naphthanoimidazolyl and 4,5-diphenylimidazolyl N donors were synthesized and used to assemble M₆L₆L′-type [M = Re­(CO)₃, L = anionic angular rigid NN donors, and L′ = flexible hexatopic N donors] spheroid metallacycles. These molecules with a diameter of ∼17 Å were obtained from Re₂(CO)₁₀, H–L (imidazole, benzimidazole, and naphthanoimidazole), and L′ [1,2,3,4,5,6-hexakis­(benzimidazol-1-ylmethyl)­benzene (L¹), L², and L³] in a one-step process. Ligands L² and L³ were characterized by elemental analysis, electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), and ¹H NMR spectroscopy. Metallacycles 1–5 were characterized by elemental analysis, ESI-TOF-MS, Fourier transform infrared spectroscopy, and single-crystal X-ray diffraction analysis. Molecules 1, 2, and 4 can be considered as metallocavitands and contain multiple solvent-accessible receptors, i.e., two metallocalix[3]­arene units and six/four calix[4]­arene-/cleft-shaped receptors, on the surface. Guests such as acetone molecules could be accommodated in the calix[4]­arene/cleft-shaped receptor of the metallocavitands.