Interaction of DNA and a series of aromatic donor–viologen acceptor molecules with and without the presence of CB[8]

Abstract

A series of 1-ethyl-1'-arylmethyl-4,4'-bipyridinium compounds is synthesized, where the aryl is phenyl (BEV), 2-naphthyl (NEV), 2-anthracenyl (AEV) or 1-pyrenyl (PEV). Among them, PEV and AEV can bind with calf thymus DNA mainly through intercalation and groove-binding modes, and both of them can be observed to photocleave plasmid pBR 322 DNA significantly under irradiation with a xenon arc lamp. After inclusion of cucurbit[8]uril (CB[8]), all of the aromatic donor-viologen acceptor compounds exhibit efficient DNA photocleavage ability. The reason is that CB[8] can inhibit the intramolecular backwards electron transfer in the aromatic donor-viologen acceptor molecule, prolonging the lifetime of the charge separated excited state to some extent. These studies bring a new subject in DNA photocleavage research and a potential application of the host-guest supramolecular system.

Study of the Counter Anions in the Host‐Guest Chemistry of Cucurbit[8]uril and 1‐Ethyl‐1′‐benzyl‐4,4′‐bipyridinium

“…In the CB[8] host-guest chemistry, viologen derivatives were often used as guest molecules because of their outstanding electron-accepting properties. The inclusion of the methyl viologen (N,N-dimethyl-4,4-bipyridinium, MV 2+ ) and derivatives in CB[8] has been studied extensively both by ourselves [18–26] and others [2–14] in recent years, and the results show that CB[8] can bind with MV 2+ and its radical MV +• strongly. In particularly, CB[8] can form a 2 : 1 including complex with the radical to form a dimer (MV +• ) 2 /CB[8]; the dimerization constant of MV +• in the presence of CB[8] is estimated to be 2 × 10 7  M −1 , which is about 10 5 times larger than that of MV +• alone in aqueous media.…”

“…As we know, viologen derivatives have two positive charges in the structure, and two counter anions are needed to keep the molecule neutral [3, 18–26]. Although the host-guest chemistry of viologen guest molecules with CB[8] has been studied widely, to the best of our knowledge, no attempt has been made to examine the effect of the counter anion in the CB[8] host-guest system.…”

“…In the previous study [26], 1-ethyl-1′-benzyl-4,4′-bipyridinium dichloride (BEV-Cl 2 ) and CB[8] are found to form inclusion complex. It is assumed that the effective positive charge character on the bipyridinium fragment could be affected by the associated counter anions, which could in turn influence the efficiency of CB encapsulation.…”

Photoresponsive Supramolecular Complexes as Efficient DNA Regulator

“…The interaction of 1 , 2 , and their CB[8]-bound complexes with ct-DNA was preliminarily examined by UV/vis spectroscopy26. As seen in Figures S52a and S53a, the absorbance of trans - 1 and trans - 2 was slightly decreased upon addition of ct-DNA, suggesting that the naked compounds had a weaker interaction with DNA double helix.…”

“…These phenomena could be contributed to the photoinduced electron transfer process, through which the photo-activated viologen moiety in these [2]pseudorotaxanes can generate the reactive oxygen species to destroy the DNA structures2629. Comparatively, no DNA damage was observed with the supramolecular complexes of trans - 1 ⊂CB[8] and trans - 2 ⊂CB[8] in the dark or by irradiating pBR322 DNA alone in the control experiments (Supplementary Figure S49), indicating that the DNA damage was attributed to the reduced viologen in cis - 1 ⊂CB[8] and cis - 2 ⊂CB[8].…”