title: Influence of Water in the Photogeneration and Properties of a Bifunctional Quinone Methide.
abstract: Quinone methides (QM) are crucial reactive species in molecular biology and organic chemistry, with little known regarding the mechanism(s) for the generation of short-lived reactive QM intermediates from relevant precursors in aqueous solutions. In this study, several time-resolved spectroscopy methods were used to directly examine the photophysics and photochemical pathways of 1,1'-(2,2'-dihydroxy-1,1'-binaphthyl-6,6'-diyl)bis(N,N,N-trimethylmethanaminium) bromide (BQMP-b) from initial photoexcitation to the generation of the key reactive binol QM intermediate (BQM) in aqueous solution. The fluorescence of BQMP-b is effectively quenched with a small amount of water, which suggests an excited state intramolecular proton transfer (ESIPT) occurs. The kinetics isotope effects observed in femtosecond and nanosecond time-resolved transient absorption experiments provide evidence for the participation of water molecules in the BQMP-b singlet excited state ESIPT process and in the subsequent -HNMe3+group release and ground state intramolecular proton transfer that give rise to production of the reactive BQM intermediate. Nanosecond time-resolved resonance Raman (ns-TR3) measurements were also employed to investigate the structure and properties of several intermediates, including the key reactive BQM in aqueous solution. The ns-TR3and density functional theory (DFT) computational results were compared, and this indicates the binol moiety and water molecules both have important roles in the characteristics and structure of the key reactive BQM intermediate produced from BQMP-b. The results presented here also provide new benchmark characterization of bifunctional quinone methide intermediates that can be utilized to guide direct time-resolved spectroscopic study of the alkylation and interstrand cross-linking reactions of quinone methides with DNA in the future.
authors.affiliation: Department of Chemistry, University of Hong Kong , Pokfulam Road, Hong Kong S.A.R., P. R. China.
authors.forename: Lili
authors.initials: L
authors.lastname: Du
authors.affiliation: Department of Chemistry, University of Hong Kong , Pokfulam Road, Hong Kong S.A.R., P. R. China.
authors.forename: Xiting
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Zhejiang Sci-Tech University , Hangzhou 310018, P. R. China.
authors.forename: Jiadan
authors.initials: J
authors.lastname: Xue
authors.affiliation: School of Pharmacy, Anhui Medical University , Meishan Road 81, Hefei 230032, P.R. China.
authors.forename: WenJian
authors.initials: W
authors.lastname: Tang
authors.affiliation: Department of Chemistry, University of Hong Kong , Pokfulam Road, Hong Kong S.A.R., P. R. China.
authors.forename: Ming-De
authors.initials: MD
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Hong Kong , Pokfulam Road, Hong Kong S.A.R., P. R. China.
authors.forename: Xin
authors.initials: X
authors.lastname: Lan
authors.affiliation: Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, P. R. China.
authors.forename: Jiangrui
authors.initials: J
authors.lastname: Zhu
authors.affiliation: Department of Chemistry, University of Hong Kong , Pokfulam Road, Hong Kong S.A.R., P. R. China.
authors.forename: Ruixue
authors.initials: R
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, P. R. China.
authors.forename: Yuxiang
authors.initials: Y
authors.lastname: Weng
authors.affiliation: Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences , Beijing 100190, P. R. China.
authors.forename: Yun-Liang
authors.initials: YL
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Hong Kong , Pokfulam Road, Hong Kong S.A.R., P. R. China.
authors.forename: David Lee
authors.initials: DL
authors.lastname: Phillips
mesh_terms: D045563:Indolequinones / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D011789:Quantum Theory; D014867:Water / Q000737:chemistry*
chemical_list: D045563:Indolequinones; D014867:Water; C068040:quinone methide