A simple approach for the synthesis of coumarin fluorescent dyes under microwave irradiation and their application in textile printing

Abstract

Purpose The purpose of this study is to successfully implement microwave irradiation for the rapid synthesis of novel fluorescent dyes. The prepared dyes are then applied for printing of polyester and polyamide by silk screen printing process. Design/methodology/approach A series of new N′-(methylene)-2-imino-2H-chromene-3-carbohydrazide derivatives 3a–r were synthesised in excellent yield and high atom economy by the Knoevenagel condensation of salicylaldehyde derivatives 1 and cyano-N′-methyleneaceto-hydrazide derivatives 2 in the presence of piperidine catalyst. The optical properties of the synthesised compounds were recorded; all of the compounds were found to be fluorescent in 1, 4-dioxane solution; they all emitted blue light (440-460 nm). This work shows that the optical properties strongly depend on the nature of the substituent, and indicate which type of substituent is favourable for a given application. It confirms that iminocoumarin derivatives could lead to a new generation of fluorescent probes, prone to easy modification of their chemical structure. These synthesised dyes are used to print polyester and polyamide fabrics using synthetic thickener in the printing paste for silk screen technique. Findings The structures of synthesised dyes were established and confirmed for the reaction products on the basis of their elemental analysis and spectral data (MS, IR and 1H-NMR). The suitability of the prepared dyestuffs for traditional printing on polyester and polyamide fabrics has been investigated. The prints obtained using the synthesised dyes were found to possess high colour strength and excellent overall fastness properties but relatively low light fastness. Research limitations/implications The synthesised fluorescent dyes were prepared by a simple reaction process in microwave. The optical properties for obtained dyes show include the fact that it will have various important applications. In addition, they were used for printing synthetic fabrics and were found to have good results. Practical implications The new fluorescent dyes’ system has excellent printing properties. Also they are superior in terms of yield, purity, colour strength and fastness properties which may lend them valuable commercial production. Originality/value The result of this work aimed to define the scope and limitation of the procedures for the synthesis of novel iminocoumarin dyes via a simple and economic way.