Synthesis of some novel quinone diimine derivatives of benzo-15-crown-5 for application in Hg 2+ recognition S. D. Jagadale, a A. D. Sawant, b P. P. Patil, a D. R. Patil, a A. G. Mulik, a D. R. Chandam, a S. A. Sankpal a and M. B. Deshmukh a * ABSTRACT: A series of novel fluoroionophore bearing derivatives of benzo-15-crown-5 were synthesized by the amination of benzo-15-crown-5 followed by condensation with different quinones in the presence of titanium tetrachloride (TiCl 4 ) and 1,4-diazabicyclo-[2.2.2]octane. The compounds were characterized by infrared, 1 H and 13 C nuclear magnetic resonance, mass spectroscopy and elemental analysis. Absorption and fluorescence spectral characteristics of these compounds were studied. It was observed that the anthraquinone derivative was acting as an Hg 2+ ion sensor. Copyright © 2013 John Wiley & Sons, Ltd. Keywords: benzo-15-crown-5 (B15C5); 4-Aminobenzo-15-crown-5 (4AB15C5); quinone diimine derivatives; emission spectroscopy; metal ion sensor Introduction Recently, macrocyclic polyethers have become ubiquitous in many fields of chemistry, material science and molecular biology (1–4). Several workers have reported modified crown ethers with chromogenic groups (5,6). It is known that, crown ether functionalized with different fluorophores is of great significance due to the sensitivity of the resulting fluorophores and the ease of monitoring the change in the optical signal. The fluorophore unit with an intramolecular charge transfer excited state is ac- customed to produce a strong optical response to the cation– macrocycle interactions (7–9). At present, there has been much interest in the synthesis of crown ether derivatives involving combinations of more than one fluoroionophore with a crown ether moiety (10–15). Such fluoroionophores can induce a specific fluorescence spectral change. Fluorescent chemosensor molecules that change their fluorescence in response to the substrate represent an extremely sensitive optical method for real-time monitoring of the molecular interactions (16–18). Such chemosensors are used as metal ion complexing agents (19), ion selective electrode (20), biological membranes (21) and other biological applications (22). There are many reports about use of steady state fluorescence spectroscopy to test the cation- complex formation abilities of chromophore imbibed crown ether moieties (23,24). Nowadays, there has been great interest to vary the structure of N=C-C=C-C=N conjugated systems to tune and acquire more favourable physical and functional properties (25). Quinone imines are important intermediates for organic synthesis and constitute potential precursors to a number of natural products (26). A num- ber of articles related to complexes of transition and non-transition metals with various substituted quinone diimine ligands have been published (27). These complexes exhibited biological activi- ties (28) and have been employed as a catalysts in olefin polymer- ization (29). Such complexes also have interesting spectral and redox (30) properties, which can be used for building molecules with fascinating electronic properties. Recognition of metal ions particularly Hg 2+ is of great interest, taking into account the toxic- ity of the metal (31). Our goal was to synthesize a fully conjugated novel benzo-15-crown-5 functionalized quinone diimine deriva- tive as optical sensor for Hg 2+ ion recognition. Experimental Crown ether and quinones were purchased from Sigma-Aldrich Chemicals Ltd. Banglore, India and all other chemicals and solvents were AR grade and used as purchased without any further purifica- tion. The progress of the reaction was monitored by thin-layer chro- matography TLC (silica gel 60 F 254 , Merck, Germany). Infrared (IR) spectra were recorded on a Perkin-Elmer spectrometer (USA), mixed with KBr and pressed into pellets, scanning from 4000 to 450/cm. The 1 H NMR and 13 C NMR were recorded on Bruker 300 AVANCE II (Switzerland) with CDCl 3 as solvent and tetramethylsilane as internal standard. Elemental analysis was conducted using the EURO Vector Elemental Analyser (USA). Melting points were determined in an open capillary tube and are uncorrected. The absorption spectra were recorded on an ultraviolet–visible near-infrared spectrophotometer Shimadzu (Model-UV-3600, Japan). The fluorescence spectra were recorded on a spectroflu- orometer (Jasco-FP 8300, USA). Deionized water is used for preparing a stock solution of Hg 2+ . * Correspondence to: Madhukar B. Deshmukh, Department of Chemistry, Shivaji University, Kolhapur, Maharashtra, India 416 004. E-mail: shubhlaxmi111@gmail.com a Department of Chemistry, Shivaji University, Kolhapur, Maharashtra, India b Department of Chemistry, Sanjay Ghodawat Institute of Technology, Atigre, Kolhapur, Maharashtra, India Luminescence 2014; 29: 586–590 Copyright © 2013 John Wiley & Sons, Ltd. Research article Received: 20 December 2012, Revised: 3 August 2013, Accepted: 7 August 2013 Published online in Wiley Online Library: 9 October 2013 (wileyonlinelibrary.com) DOI 10.1002/bio.2585 586