Multicomponent Self-Assembly of Diaminobenzoquinonato-Bridged Manganese(I) Metallosupramolecular Rectangles: Host–Guest Interactions, Anticancer Activity, and Visible-Light-Induced CO Releasing Studies

The one-pot self-assembly of Mn 2 (CO) 10, a bis-chelated diaminobenzoquinonato (ON∩ON) bridge (L), and a linear ditopic linker (N∩N) (L′) has resulted into the formation of M 4 L 2 L 2 ′-type manganese(I)-based tetranuclear metallorectangles of the general formula [{(CO) 3 Mn(μ-η 4 -L)Mn(CO) 3 } 2 (μ-(N-N) 2 )] ( 1 – 8 ), wherein L is 2,5-bis( n -butylamine)-1,4-benzoquinone ( bbbq ) and/or 2,5-bis(phenethylamino)-1,4-benzoquinone ( bpbq ) and N-N is 4,4′-bipyridine ( bpy ), trans -1,2-bis(4-pyridyl) ethylene ( bpe ), phenyl-1,4-bis(isonicotinate) ( pbin ), and N, N ′-bis(4-pyridylformamide)-1,4-benzene ( bpfb ). Metallorectangles 1 – 8 were characterized by infrared, ultraviolet–visible (UV–vis) absorption, and 1 H nuclear magnetic resonance spectroscopies, elemental analysis, and electrospray ionization-mass spectrometry. The molecular and crystal structures of 1 • n (CHCl 3 ) and coronene⊂ 3 •coronene were determined by the single-crystal X-ray diffraction method. Host–guest binding abilities of 1, 3, and 7 with coronene, pyrene, and 4,4′-dihydroxybiphenyl were investigated using UV–vis absorption and emission spectroscopic techniques. Formation of host–guest complexes was further confirmed by the single-crystal X-ray structural analysis. Absorption of spectra of these metallorectangles showed high-intensity metal–ligand charge transfer as a broad band in the visible region. In vitro cytotoxicity assays were performed on 1, 3, 5, and 7 against lung, colon, and cervical cancer cells as well as normal cells. Compounds 5 and 7 were identified as visible-light-induced CO-releasing molecules from the myoglobin assay.