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(CO), a bis-chelated diaminobenzoquinonato (ON∩ON) bridge (L), and a linear ditopic linker (N∩N) (L') has resulted into the formation of MLL'-type manganese(I)-based tetranuclear metallorectangles of the general formula [{(CO)Mn(μ-η-L)Mn(CO)}(μ-(N-N))] (-), wherein L is 2,5-bis(-butylamine)-1,4-benzoquinone () and/or 2,5-bis(phenethylamino)-1,4-benzoquinone () and N-N is 4,4'-bipyridine (), -1,2-bis(4-pyridyl) ethylene (), phenyl-1,4-bis(isonicotinate) (), and ,'-bis(4-pyridylformamide)-1,4-benzene (). Metallorectangles - were characterized by infrared, ultraviolet-visible (UV-vis) absorption, and H nuclear magnetic resonance spectroscopies, elemental analysis, and electrospray ionization-mass spectrometry. The molecular and crystal structures of •(CHCl) and coronene⊂•coronene were determined by the single-crystal X-ray diffraction method. Host-guest binding abilities of , , and 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 , , , and against lung, colon, and cervical cancer cells as well as normal cells. Compounds and were identified as visible-light-induced CO-releasing molecules from the myoglobin assay.