Synthesis, photophysical and electrochemical properties of donor-acceptor type hydrazinyl thiazolyl coumarins

• Published in: New journal of chemistry 2020-05, Vol.44 (17), p.77-716
• Main Authors: Godugu, Kumar, Gundala, Thrivikram Reddy, Bodapati, Ramakrishna, Yadala, Venkata Divya Sri, Loka, Subramanyam Sarma, Nallagondu, Chinna Gangi Reddy
• Format: Article
• Language: English
• Subjects: Aldehydes; Aromatic compounds; Chloroform; Crystallography; Electrochemical analysis; Energy levels; Fluorescence; Ketones; Molecular orbitals; Montmorillonite; NMR; Nuclear magnetic resonance; Properties (attributes); Substrates; Synthesis
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d0nj00082e

A water-mediated MCR strategy has been developed for the synthesis of donor (D)-acceptor(A) type hydrazinyl thiazolyl coumarins (HTCs) ( 4 ) in excellent isolated yields (90-98%) from a three component reaction of aromatic aldehydes/ketones ( 1 ), thiosemicarbazide ( 2 ) and 3-(2-bromoacetyl)-2 H -chromen-2-one ( 3 ) catalyzed by an environmentally compatible montmorillonite (MMT) K10 clay at RT for 20-40 min. The present MCR strategy has several advantages that include its wide-spread substrate scope, eco-compatibility, short reaction times and products that do not require chromatographic purification. Besides, the method is simple to perform, it is easy to construct C-N, C&z.dbd;N and C-S bonds in one pot and the reaction can be scaled up to a gram level. Moreover, the catalyst can be reused 7 times without significant change of activity. The photophysical properties of the synthesized D-A type HTCs are also studied and it was noticed that the fluorescence properties can be varied with the position of electron donating group on the aromatic ring of aldehyde/ketone of HTCs. Most of the compounds exhibited bright fluorescence in chloroform (1.0 × 10 −5 M) with emission maxima ranging from 409 to 511 nm and large Stokes shifts. Further, the HOMO and LUMO energy levels of the HTCs are found in the range from −5.65 eV to −5.22 eV and −2.67 eV to −2.17 eV, respectively, and in good agreement with the reported hole transporting materials. A practical green MCR strategy has been developed for the synthesis of D-A type hydrazinyl thiazolyl coumarins catalyzed by an environmentally compatible MMT K10 clay in water at RT.