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 boolean AND ON) bridge (L), and a linear ditopic linker (N boolean AND N) (L') has resulted into the formation of M4L2L2'-type manganese(I)-based tetranuclear metallorectangles of the general formula [{(CO)(3)Mn(mu-eta(4)-L)Mn(CO)(3)}(2)(mu-(N-N)(2))] (1-8), wherein L is 2,S-bis(n-butylamine)-1,4-benzoquinone (bbbq) and/or 2,S-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 H-1 nuclear magnetic resonance spectroscopies, elemental analysis, and electrospray ionization-mass spectrometry. The molecular and crystal structures of 1.n(CHCl3) and coronene subset of 3 center dot 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.