Photoinduced reactivity and cytotoxicity of a series of zinc(II)–flavonolate derivative complexes

Abstract A series of Zn(II)-based complexes as photoinduced carbon-monoxide-releasing molecules (photoCORMs), viz. ( L )Zn( R )]ClO 4 with L  = tris(pyridine-2-ylmethyl)amine (TPA), N , N -((5-estermethyl-2-pyridyl)methyl)-bis(2-pyridylmethyl) amine (5-COOCH 3 TPA), N , N -(bis(5-estermethyl-2-pyridyl)methyl)-(2-pyridylmethyl) amine [(5-COOCH 3 ) 2 TPA], or N , N -((6-estermethyl-2-pyridyl)methyl)-bis(2-pyridylmethyl) amine (6-COOCH 3 TPA) and R  = 4-dimethylaminoflavonol [4-N(Me) 2 FLH], 4-diethylaminoflavonol [4-N(Et) 2 FLH], or 4-methoxyflavonol (4-MeOFLH), have been prepared and characterized. When dissolved in CH 3 CN or 1:1 H 2 O:dimethylsulfoxide (DMSO) in presence of O 2 , visible light ( λ max ranging from 417 to 462 nm) induced dioxygenase-type reactions to release CO quantitatively from these complexes. Moreover, the intracellular uptake and CO releasing reactivity were confirmed by the change of their fluorescent properties observed under fluorescence microscopy. The cytotoxicity of the complexes demonstrates that they exhibit good biocompatibility in the concentration range from 1 to 50 μM. The solid complexes are stable in air for more than 60 days, and their aqueous solutions are also stable for 96 h under anaerobic or dark condition. The remarkable stability and biocompatibility of the complexes are indispensable properties for use in pharmaceutical chemistry. Graphic abstract