Impact of donor acceptor alternation on optical power limiting behavior of H Shaped thiophene imidazo[2,1-b] [1,3,4]thiadiazole flanked conjugated oligomers

Abstract

A new series of four D A D configured conjugated oligomers with H type structure, possessing two thiophene imidazo [2,1-b][1,3,4]thiadiazole branches and thiophene (TIT), thiophene 1,3,4-oxadiazole thiophene (TITO), thiazolo [5,4-d]thiazole (TITz), phenyl thiazolo [5,4-d]thiazole phenyl (TIPTz) units as central core moieties were efficiently synthesized. These core moieties were specifically selected to increase the planarity, rigidity, stability, extend the ? conjugation and to understand the influence of central core on nonlinear absorption coefficient (?eff) and optical limiting behavior of the synthesized oligomers. The structure-property relationships of these oligomers were established by the optical absorption (UV Vis), electrochemical (CV) and theoretical (DFT) studies. The effective two photon absorption of oligomers was confirmed by single beam Z scan analysis. The exceptional increase in nonlinear response was achieved with the oligomers TITO and TIPTz with nonlinear absorption coefficient (?eff) of 1.62 and 2.71 10?10 m W?1, and limiting thresholds of 6.02 and 3.14 J cm?2, respectively, which suggest that these oligomers could be potent materials for practical applications in laser photonics. 2020 Elsevier Ltd