The effect of hydrogen bonding interactions between 2-[4-(dimethylamino)phenyl]-3-hydroxy-4H-chromene-4-one in the ground and excited states and dimethylsulfoxide or methanol on electronic absorption and emission transitions Vasyl G. Pivovarenko a, * , Agnieszka Wro ´blewska b , Jerzy Blazejowski b a Faculty of Chemistry, Kyiv Taras Shevchenko National University, Volodymyrska 64, Kyiv 01033, Ukraine b Faculty of Chemistry, University of Gdan ´sk, J. Sobieskiego 18, Gdan ´sk 80-952, Poland Received 24 February 2004; revised 5 May 2004; accepted 5 May 2004 Available online 12 September 2004 Abstract The absorption and fluorescence spectra of 2-[4-(dimethylamino)phenyl]-3-hydroxy-4H-chromene-4-one in benzene or toluene and in the presence of methanol (proton donor) or the highly polar dimethylsulfoxide (proton acceptor) were measured and analyzed from the point of view of the potential influence of hydrogen bonding interactions on the spectral characteristics. The changes in the positions of the spectral maxima were interpreted as a result of the formation of complexes between the title compound and specifically interacting molecules present in the system. The structure and properties of possible complexes were predicted at the PM3 (ground state) and PM3/CI (excited state) levels of theory. The unique spectral features of the compound investigated, to a large extent affected by intramolecular proton transfer in the excited state and by specific interactions with certain components in the medium, can be utilized to determine the properties of solutions. q 2004 Elsevier B.V. All rights reserved. Keywords: 2-[4-(Dimethylamino)phenyl]-3-hydroxy-4H-chromene-4-one; Electronic absorption; Fluorescence; Hydrogen bonding interactions; Utilization in the determination of solution properties 1. Introduction Flavonols (derivatives of 3-hydroxy-2-phenyl-4H- chromene-4-one (dimethylamino-3-hydroxyflavone) (1) (Scheme 1)) are of considerable interest because of their possible application as multi-channel fluorescence probes, inter alia for the investigation of intermolecular interactions in liquid systems [1–4]. Their attractive features are related to the fact that the compounds exhibit two distinctly separate bands in the fluorescence spectra—originating from the N and T forms (Scheme 1)—the positions and intensities of which depend on the properties of the medium. The dual fluorescence of flavonols can be explained by Excited State Intramolecular Proton Transfer (ESIPT) [5]. This phenomenon, to a considerable extent dependent on the features of the medium, enhances the differentiation of spectral parameters relevant to the N and T forms, which are obtainable by steady-state fluorometry. Owing to this unique feature, several flavonols appear to be convenient probes for the analysis of the constitution of micelles [1,6–8] and phospholipid vesicles [2,3,8–12], and also in the fluor- escence recognition of cations of different radii [13,14]. Several attempts have been made to obtain information on the composition of a solution with flavonols as fluorescent probes [15–17]. Among them is a method, developed by Liu et al., for the detection of water in acetone, in which measurements of the fluorescence intensity of 2-[4-(dimethylamino)phenyl]-3-hydroxy-4H-chromene- 4-one (2, Scheme 1) were utilized [17]. In similar vein is a highly promising approach proposed by Klymchenko and Demchenko for the simultaneous determination of three physico-chemical parameters of a liquid phase from 0022-2860/$ - see front matter q 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2004.05.035 Journal of Molecular Structure 708 (2004) 175–181 www.elsevier.com/locate/molstruc * Corresponding author. Tel.: C38-44-239-33-12; fax: C38-44-220- 83-91. E-mail address: pvg@univ.kiev.ua (V.G. Pivovarenko).