fac-[M(CO)3] (M = Mn or Re)-based capped metallacalix[3]arenes.

• Self-assembly of fac-[M(CO)3] (M = Mn or Re)-based neutral heteroleptic metallocages. • 5,6-di-(methoxycarbonyl)-benzimidazolyl substituted N donor-based tripodal ligand. • Metallocalix[3]arenes capped with ester functionalized flexible tritopic framework. A flexible tritopic ligand, 1,3,5-tri(5,6-di-(methoxycarbonyl)-benzimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (Tebim) was designed, synthesized and characterized. Six neutral heteroleptic fac -[M(CO) 3 ]-based capped metallacalix[3]arenes with/without six or twelve ester decorated motifs were synthesized via one-pot approach using M 2 (CO) 10 (M = Mn or Re), rigid angular bidentate ligand (benzimidazole (H-bim) or 5,6-di-(methoxycarbonyl)-benzimidazole (H-ebim)), and tritopic ligand (1,3,5-tri(benzimidazol-1-ylmethyl)-benzene (Tbim) or Tebim). All capped metallacalix[3]arenes are characterized using FT-IR, 1H NMR spectroscopy and mass spectrometry. The 1H NMR spectra for all the complexes displayed a simple and symmetrical pattern with characteristic upfield and downfield shifts for the protons of both the coordinated ligands, which signifies that synthesized capped metallacalix[3]arenes retains the structural framework in the solution. Further, the molecular structures of 1 and 3b were confirmed by single crystal X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]