naa a22 4500 510734294 CHVBK 20180411083004.0 cr unu---uuuuu 180411e20130701xx s 000 0 eng 10.1007/s12039-013-0428-4 doi (NATIONALLICENCE)springer-10.1007/s12039-013-0428-4 Molecular aggregation, solvato- and acidochromic properties of symmetrical ketocyanines [Elektronische Daten] [TAREK FAYED, MOHAMMED EL-MORSI, MARWA EL-NAHASS] The absorption and fluorescence spectral characteristics of some symmetrical ketocyanine dyes have been investigated in different solvents of various polarities using steady-state absorption and emission spectroscopic techniques. The absorption spectral features are less sensitive to the solvent characteristics than the corresponding fluorescence spectra. A large excited state dipole moment parallel to the smaller ground state dipole moment was calculated. The large dipole moment change with the strongly solvatofluorochromic behaviour, as the solvent polarity increases, demonstrates the formation of an intramolecular charge-transfer (ICT) excited state, which is confirmed by theoretical calculation using semiempirical PM3 method. Also, the effect of dye concentration on the electronic absorption spectra for the investigated dyes has been studied in ethanol. In addition, the acidochromic behaviour of these dyes has been studied using sulphuric acid at different H o values. A progressive red-shift in the absorption and emission spectra has been observed upon increasing the concentration of sulphuric acid with dramatic changes in colour. This suggests the design of potential optical sensors for probing acidity of the medium or water content in sulphuric acid. The calculated excited state protonation constants $\left( {\mbox{p}K_{\rm a}^\ast } \right)$ are lower than p $K_{\rm a\thinspace}$ values calculated for the ground state, indicating that the investigated ketocyanines become more basic in the first excited singlet state. Graphical Abstract Significant changes in the spectral characteristics of the investigated ketocyanines suggest that they can serve as good reporters of solvent polarity, hydrogen-bond donating ability and the acidity of the medium. The colour change upon increasing sulfuric acid concentrations may lead to design of potential optical sensors for probing acidity of the medium. Indian Academy of Sciences, 2013 Ketocyanine dye nationallicence solvatochromic nationallicence intramolecular charge-transfer (ICT) nationallicence molecular aggregation nationallicence acidochromic nationallicence protonation constant nationallicence FAYED TAREK Department of Chemistry, Faculty of Science, Tanta University, 31527, Tanta, Egypt aut EL-MORSI MOHAMMED Department of Chemistry, Faculty of Science, Tanta University, 31527, Tanta, Egypt aut EL-NAHASS MARWA Department of Chemistry, Faculty of Science, Tanta University, 31527, Tanta, Egypt aut Journal of Chemical Sciences Springer India 125/4(2013-07-01), 883-894 0974-3626 125:4<883 2013 125 12039 https://doi.org/10.1007/s12039-013-0428-4 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s12039-013-0428-4 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- FAYED TAREK Department of Chemistry, Faculty of Science, Tanta University, 31527, Tanta, Egypt aut NATIONALLICENCE 700 1- EL-MORSI MOHAMMED Department of Chemistry, Faculty of Science, Tanta University, 31527, Tanta, Egypt aut NATIONALLICENCE 700 1- EL-NAHASS MARWA Department of Chemistry, Faculty of Science, Tanta University, 31527, Tanta, Egypt aut NATIONALLICENCE 773 0- Journal of Chemical Sciences Springer India 125/4(2013-07-01), 883-894 0974-3626 125:4<883 2013 125 12039 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer