A selective fluorescent receptor for the determination of nickel (II) in semi-aqueous media Umesh Fegade a,b , Jaromir Marek c , Rahul Patil a , Sanjay Attarde b , Anil Kuwar a,n a School of Chemical Sciences, North Maharashtra University, Jalgaon 425001, MS, India b School of Environmental and Earth Sciences, North Maharashtra University, Jalgaon 425001, MS, India c Central European Institute of Technology, Masaryk University, Kamenice 5, 62500 Brno, Czech Republic article info Article history: Received 31 July 2013 Received in revised form 26 September 2013 Accepted 27 September 2013 Available online 7 October 2013 Keywords: (7E,8E)-N1′N3′-bis(1-(2-hydroxyphenyl) ethylidene) malonohydrazide Fluorescence probe Stability constant abstract The malonohydrazide based fluorescent probe (7E,8E)–N1′,N3′-bis(1-(2-hydroxyphenyl)ethylidene) malonohydrazide (receptor 5) was designed and synthesized. It was confirmed by spectroscopic methods and the single crystal X-ray method. The receptors 5 show strong intramolecular hydrogen bonding which is useful in host–guest complexation. The fluorescence spectra of receptor 5 have shown distinct enhancement with the addition of Ni 2 þ ion over other surveyed cations. The stability constant was obtained by Benesi–Hildebrand, Scatchard and Connor's fitting methodologies. The 1:1 stoichiometry of the host–guest complexation was confirmed by Job's continuous variation method. & 2013 Elsevier B.V. All rights reserved. 1. Introduction Design and synthesis of a selective fluorescent probes for the sensing of ionic species important from the environmental and material science point of view, mainly heavy metal ions, is a topic of growing interest in supramolecular chemistry [1–3]. A signifi- cant effort has been dedicated to the improvement of Ni 2 þ selective fluorescent receptors in the last few decades. However, in most cases fluorescence changes can only be observed in non- aqueous solvent and as well as gets affected by the common interference of other metal ions [4–9], which bound the limits for their analytical application in real samples analysis. Therefore, the development of highly sensitive and selective fluorescent receptor for Ni 2 þ in aqueous solution is very important and challenging area for the researchers [10–13]. Nickel can be found in the plasma of the blood. The absence of nickel from the plasma or red cells of a few subjects may be regarded as evidence against the existence of a physiologic function for this element [14]. In vitro nickel activates arginase, carboxylase and trypsin, and it may inhibit acid phosphatase. There is evidence that it affects the clotting mechanism by stabilizing the labile factor [15,16]. Nickel deliberation is a potential health hazard to fauna and flora if it exceeds the normal level than the cellular needs. Nickel toxicity can cause acute pneumonitis, dermatitis, asthma, eczema, cancer of lungs, sinus, stomachaches, unfavorable effects on blood (increases red blood cells) and kidneys (increases protein in urine) other disorders of respiratory system and central nervous system [17]. In current article, we report the synthesis of (7E,8E)–N1′,N3′- bis(1-(2-hydroxyphenyl)ethylidene) malonohydrazide (receptor 5) and studied its binding properties towards Cr 3 þ , Mn 2 þ , Fe 3 þ , Co 2 þ , Ni 2 þ , Cu 2 þ , Zn 2 þ , Cd 2 þ , Hg 2 þ , Pb 2 þ and Bi 3 þ in DMSO/H 2 O (1:1, v/v). Receptor 5 has interestingly shown significant enhance- ment in fluorescence emission maxima in the semi-aqueous phase with Ni 2 þ metal ion. This ability to grant fluorescent enhancement in semi-aqueous phase makes its application possible in the area of biology, environmental and material sciences. 2. Experimental 2.1. Chemical and apparatus All commercial grade chemicals and solvents were purchased from Sigma-Aldrich and used without further purification. 1 H-NMR and 13 C-NMR spectra were recorded on Varian NMR mercury System 300 spectrometer operating at 300 and 75 MHz in DMSO-d 6 solvent. The fluorescence spectra were recorded in DMSO/H 2 O (1:1, v/v) namely on Fluoromax-4 spectrofluorometer and Shimadzu UV- 24500 at room temperature using 1 cm pathlength cell. 2.2. Synthesis of (7E,8E)–N1′,N3′-bis(1-(2-hydroxyphenyl) ethylidene)malonohydrazide (receptor 5) Malonohydrazide (3) was synthesized from condensation of one mole diethyl malonate (0.32 g, 2 mM) with two moles of Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jlumin Journal of Luminescence 0022-2313/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jlumin.2013.09.075 n Corresponding author. Tel.: þ91 257 2257 432; fax: þ91 257 2257 403. E-mail address: kuwaras@gmail.com (A. Kuwar). Journal of Luminescence 146 (2014) 234–238