Journal of Materials Science Research; Vol. 8, No. 3; 2019 ISSN 1927-0585 E-ISSN 1927-0593 Published by Canadian Center of Science and Education 6 Spectroelectrochemical Investigation of 4-Dicyanomethylene 2,6-Dimethyl-4H-Pyran (DDP) Dye with Guanidine Hydrochloride (GuHCl) in Water Somasundaram Gayathri 1 , Rajaraman Vasanthi 1 , Mahalingam Vanjinathan 1 , & Rajendran Kumaran 1 1 Department of Chemistry, Dwaraka Doss Goverdhan Doss Vaishnav College (Autonomous), Gokul Bagh, E.V.R. Periyar Road, Arumbakkam, Chennai, Tamil Nadu, India Correspondence: Rajendran Kumaran, Department of Chemistry, Dwaraka Doss Goverdhan Doss Vaishnav College (Autonomous), 833, Gokul Bagh, E.V.R. Periyar Road, Arumbakkam, Chennai 600 106, Tamil Nadu, India. Tel: 091-44-2475-6655. E-mail: kumaranwau@rediffmail.com Received: June 1, 2019 Accepted: July 5, 2019 Online Published: July 15, 2019 doi:10.5539/jmsr.v8n3p6 URL: https://doi.org/10.5539/jmsr.v8n3p6 Abstract Interaction of guanidine hydrochloride (GuHCl) with 4-dicyanomethylene-2,6-dimethyl-4H-pyran (DDP) dye were investigated by photophysical and electrochemical techniques. An enhancement in the fluorescence intensity and formation of an isosbestic point revels that the ground state and excited state properties of DDP dye. The nature of interaction between DDP dye and GuHCl is predominantly through hydrogen-bonding even thoughelectrostatic interaction in aqueous phase operate. The existence of electrostatic interaction by current response function describes that the shift in anodic peak potential towards less positive value indicate electrostatic binding. The existence of more than one microenvironment of DDP dye in aqueous phase is elucidated by Electrochemical Impedence Spectroscopy (EIS) studies through Nyquist plots. These plots signify that there exist at least three different micro environments or dye existing in different fluorescence lifetimes with varying of amplitude. Fluorescence spectral techniques along with electrochemical studies are used as efficient tools to elucidate the nature of interaction of a water soluble probe with hydrogen-bonding solutes is elucidated in our study. Keywords: DDP Dyes, Guanidine Hydrochloride, Hydrogen-Bonding, Fluorescence Emission, Fluorescence Lifetime, Cyclic Voltammetry, Electrochemical Impedance Spectroscopy 1. Introduction 4-Dicyanomethylene-2,6-dimethyl-4H-pyran (DDP) dye is a water soluble fluorophore, that exhibit electroluminescent properties also. The structure of DDP dye is similar to that of DCM type dye (Woods, 1958; Hammond, 1979; Meyer & Mialocq, 1987; Hsieh & Chen, 2007; Zarins, Jubels, & Kokars, 2011) which is a well known ICT type dye.DDP dye has a strong acceptor group (dicyanomethylene -C(CN) 2 ) in 4 th position and a donor moiety (methyl) substituted in 2 nd and 6 th positions. DDP dye possesses a significant advantage over DCM dye due to its better solubility in water and its photophysical property is distinctly different from DCM dye. There is no possibility of Twisted Intramolecular Charge Transfer (TICT) phenomenon unlike DCM dye such that the complexity over DCM dye is completely eliminated.Further, the significant edge over DCM dye is that the DDP dyeexhibits a single broad emission maxima in the visible regionwhereas DCM dye results in abroader spectra very near to the NIR region accompanied with dual emissive character.As reported in the literature pyranylidene derivatives as fluorophores are widely applied as coating materials in OLED substances and they play a major role as dopant in a polymer matrix at limited concentration which is of importance in the field of optoelectronics. Red-emitter pyranylidene-type compound usually have high luminescence quantum yield but their chromaticity is less in the presence of mono electron donor substituents (Zarins, Jubels, & Kokars, 2011). On the contrary, DDP dye exhibit excellent luminescence character in the presence of more electron releasing moieties and acts as an ideal is used as the host molecule. The present study involves Guanidine Hydrochloride (GuHCl) as the guest molecule and the role of GuHCl on the photophysical and electrochemical properties of DDP dye is established using fluorescence approach assisted by impedance spectral studies. The interaction of water soluble dyes exhibiting Intramolecular Charge Transfer (ICT) and Photoinduced