Photoinduced intramolecular charge transfer and photophysical characteristics of (2Z)-3-[4-(dimethylamino) phenyl]-2-(2- methylphenyl) prop-2-ene-nitrile (DPM) in different media Abdullah M. Asiri a, b , Samy A. El-Daly a, c, * , Khalid A. Alamry a , Muhammad Nadeem Arshad b , Mehboobali Pannipara a a Department of Chemistry, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia b Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia c Department of Chemistry, Faculty of Science, Tanta University, Tanta, Egypt article info Article history: Received 20 April 2015 Received in revised form 20 May 2015 Accepted 22 May 2015 Available online 9 June 2015 Keywords: Cyano stilbene derivative Effect of solvents Dipole moment Photophysical parameters Micellization Medium of acidity abstract A new fluorophore, (2Z)-3-[4-(dimethylamino) phenyl]-2-(2-methylphenyl) prop-2-ene-nitrile (DPM), was synthesized by knoevenagel condensation of 4-(dimethylamino) benzaldehyde and 2-methylbenzyl cyanide in ethanol using NaOH as base. The electronic absorption and emission characteristic of DPM was studied in different solvents. The X-ray crystallographic structure of DPM was also investigated. A crystalline solid of DPM gives a strong green emission at about 533 nm; these phenomena are important for the application of DPM dye in organic photo emitting diode. DPM exhibits a red shift in its emission spectrum as solvent polarity increases, indicating a large change in the dipole moment of dye molecule upon excitation due to intramolecular charge transfer in excited DPM*. The fluorescence quantum yield depends strongly on the properties of the solvents, which was attributed to positive and negative sol- vatokinetic effects. The DPM dye displays solubilization in cationic (CTAB) micelle and could be used as a probe to determine the critical micelle concentration (CMC) of CTAB. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Stilbenes and its derivatives are well known photoreactive organic compounds, have been a great interest for researchers for many decades owing to their wide variety of applications in many areas of science. Upon photo excitation, stilbene-like molecules undergo various internal processes that make them as a model molecule for researchers in many branches of research. The prop- erties of stilbene derivatives can be tuned, upon interaction with light, are the main theme for their exploitation in optoelectronic, optical storage devices and optical brighteners [1e5]. The substit- uent effect play a prominent role in the photophysics and photo- chemistry of stilbene derivatives, hence structurally modified stilbene based luminophores have become a subject of intense research in various aspects of science that interface with physics, materials chemistry, biology, and medical science. Pi-conjugated organic compounds containing a donor and acceptor group at the opposite end separated by an ethenyl bridge show a phenomenon called intramolecular charge transfer (ICT) [6] upon photo excitation and therefore, most of the studies on these type of compounds are focused on the control or utilization of the ICT effect. Compounds of this class shows dual emission in polar solvents; one originated from their locally excited state and the other from the ICT state. The latter produce the large change in dipole moment that is sensitive to solvent polarity and hence provides a tool for the studies of the polarity and viscosity of media in the vicinity of a solute molecule [7e9]. However, instead of having an acceptor group at the opposite end of donor group; compounds containing an acceptor group in the a-position of ethylenic bond also exhibits ICT state and solvent sensitivity. Moreover these pi-conjugated molecules can be functionalized to improve their properties by chemical modification. This paper presents the synthesis, characterization and photophysical behavior of a cyano stilbene derivative, (2Z)-3-[4-(dimethylamino) phenyl]-2-(2-methylphenyl) prop-2-enenitrile (DPM) in different solvents as well as in cationic and anionic micelles. The pKa, pKa* and single crystal X-ray characterizations were also investigated. * Corresponding author. King Abdulaziz University, P.O. Box 80302, Jeddah 21589, Saudi Arabia. E-mail address: samyeldaly@Yahoo.com (S.A. El-Daly). Contents lists available at ScienceDirect Journal of Molecular Structure journal homepage: http://www.elsevier.com/locate/molstruc http://dx.doi.org/10.1016/j.molstruc.2015.05.048 0022-2860/© 2015 Elsevier B.V. All rights reserved. Journal of Molecular Structure 1098 (2015) 153e160