Inclusion complex formation of ternary system: Fluoroscein-p-sulfonato calix[4]arene-Cu 2+ by cooperative binding Sharadchandra Gawhale a , Ankita Jadhav b , Nilesh Rathod b , Dipalee Malkhede b , Gajanan Chaudhari c,⇑ a Department of Applied Chemistry, AISSMS-CoE, Pune, India b Department of Chemistry, Savitribai Phule Pune University, Pune, India c Department of Chemistry, Shri. Shivaji Science College, Amravati, India highlights  The complexation of ternary system of fluorescein, p-SCX4 and Cu 2+ were investigated.  The binding constants and life time measurements were established.  NMR and IR spectroscopic analysis studied for possible interaction in system.  p-SCX4 is found efficient host for Cu 2+ and fluorescein. graphical abstract article info Article history: Received 17 September 2014 Received in revised form 12 March 2015 Accepted 27 March 2015 Available online 16 April 2015 Keywords: Para sulfonato calix[4]arene Fluorescein (FL) Ternary system Cooperative binding abstract The aqueous solution of fluorescein-para sulfonato calix[4]arene-metal ion complex has been studied based on absorption, fluorescence, 1 H NMR and FTIR spectroscopic results. It was found that the fluores- cence intensity quenched regularly upon addition of pSCX4 and metal ion. The quenching constants and binding constants were determined for pSCX4–FL and pSCX4-FL–Cu 2+ systems. 1:1 stoichiometry is obtained for pSCX4–Cu 2+ system by continuous variation method. The NMR and IR results indicates the interaction among FL, pSCX4 and Cu 2+ . The combined results demonstrate the cooperative binding to design the complex for ternary system. The life time for binary and ternary system has been studied. Ó 2015 Elsevier B.V. All rights reserved. Introduction Calixarenes and their derivatives have been attracting much attention as novel types of interesting host compounds. Their recognition and discrimination functionality for metal ions is one of their remarkable features that provide high potential as specific ionophores [1–4]. The upper and lower rims of calixarenes can be synthetically modified as per required application. Sulfonation of the calixarene at the upper rim facilitates water solubility [5], which has hydrophilic sulfonate groups on the upper rim and hydrophobic hydroxyl groups on lower rim of the calixarene cav- ity. The cone like structure of para sulfonato calix[4]arene (pSCX4) is stabilized by the planar H-bonding of the O–H groups at the narrow end of the molecule [6]. pSCX4 with a p-electron rich hydrophobic cavity and the strong hydrophilic nature of the upper rim has become increasingly important in the fields of supramolec- ular chemistry and crystal engineering [7]. The water soluble cal- ixarene sulfonates have been studied on the binding with several dyes [8–12]. Selective recognition of metal ions is of immense importance to environmental and biological point of view. During the last decade, http://dx.doi.org/10.1016/j.saa.2015.03.103 1386-1425/Ó 2015 Elsevier B.V. All rights reserved. ⇑ Corresponding author. Tel.: +91 721 2660855; fax: +91 721 2665485. E-mail address: gnchaudhari@gmail.com (G. Chaudhari). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 148 (2015) 382–388 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa