SHORT COMMUNICATION Urea Based Dipodal Fluorescence Receptor for Sensing of Fe 3+ Ion in Semi-Aqueous Medium Umesh Fegade & Hemant Sharma & Sanjay Attarde & Narinder Singh & Anil Kuwar Received: 6 July 2013 /Accepted: 2 September 2013 /Published online: 27 September 2013 # Springer Science+Business Media New York 2013 Abstract Urea based fluorescent chemosensor 1 was synthe- sized. Receptor 1 shows unique selectivity for the Fe 3+ ion and no such significant response was noticed with other metal ions (Cr 3+ , Mn 2+ , Co 2+ , Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ , Pb 2+ and Bi 3+ ) in DMSO/H 2 O (50:50,v/v) semi-aqueous solution. The binding features have been established by absorption and fluorescence spectroscopic methods. The binding constant (K) values obtained from Benesi-Hildebrand, Scatchard and Connor plot for receptor 1 is (8.3±0.3) × 10 3 M -1 and has good detection limit 0.7 μ M. The stoichiometry of 1. Fe 3+ complex was confirmed by mass spectroscopy and Job’ s plot. Keywords Dipodal receptors . Semi-aqueous medium . Binding constant Introduction The architecture of noncovalent bonding interactions array in the construction of host molecules for selective complexation with guest molecules is on the verge of getting transferred towards non-cyclic analogues of crown ether, cryptands, cy- clodextrins and spherends because of their solubility problem. Now a day, noncyclic receptors have been made to develop the field of supramolecular chemistry in which the molecular recognition, transport and catalysis phenomena have been deeply studied with the hope of shedding light on enzymatic and more complicated biological processes [1–3]. Over the past few decades, noncyclic compounds also have been utilized as the essential synthetic targets for further applica- tions in host –guest chemistry [ 4–6]. Noncyclic compounds con- taining multiples sites for noncovalent bonding interaction have gained considerable attention because of their ability of complex- ation towards broad range of analytes like ionic and/or neutral/ non-ionic molecules [ 7]. With the plan of synthesis of metallo- supramolecular complexes which can act as sensors and precur- sors, we made an attempt to design the ligands having selective and significant binding abilities towards various metal ions. Among transition metal ions Fe 3+ , Co 2+ and Zn 2+ have con- siderable biological importance and play significant role in many biochemical processes. The human body contains four grams of iron [ 8]. Most of the iron present in biological systems is tightly associated with enzymes and specialized transport and storage proteins and found in hemoglobin, the red pigment in the eryth- rocytes and rest of stored in ferretin. It plays a vital role in oxygen transfer processes in DNA and RNA synthesis. The deficiency of Fe 3+ causes anaemia, hemochromatosis, liver damage, diabetes, Parkinson’ s disease and cancer. Accumulation of copper and iron leads to over production of H 2 O 2 in tissues; causes oxidative stress and neurodegenerative diseases [9–12]. Herein, we have paid attention towards synthesis and de- signing of fluorescent sensors that utilize photoinduced electron transfer (PET) to translate a cation binding event into a fluores- cence signal. Generally these types of molecules were mostly used as an anion sensor due to the presence of amide groups but in the present work, we have reported a fluorescent sensor 1 designed for selective recognition of iron. Coordination sites in the receptors 1 show that there are two amide groups along with hydroxyl groups (Scheme 1). The binding ability of receptors 1 with Cr 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ ,Zn 2+ , Cd 2+ , Hg 2+ , U. Fegade : A. Kuwar (*) School of Chemical Sciences, North Maharashtra University, Jalgaon 425001, MS, India e-mail: kuwaras@gmail.com H. Sharma : N. Singh (*) Department of Chemistry, Indian Institute of Technology, Ropar, Rupanagar 140001, Punjab, India e-mail: nsingh@iitrpr.ac.in U. Fegade : S. Attarde School of Earth and Environmental Sciences, North Maharashtra University, Jalgaon 425001, MS, India J Fluoresc (2014) 24:27–37 DOI 10.1007/s10895-013-1297-4