Figure-02: Carbazole-Donor Based Organic Dyes (a) Dye-1(D1); (b) Dye-2(D2); (c) Dye-3(D3) [23]
In order to get structure of D1, carbazole dendritic was attached with thiophene bridge comprising of 3 thiophene rings connected with each other via carbon atoms. The carbazole dendritic was attached to thiophene bridge at 125o in order to get non-planer structures where the third thiophene ring was connected with carbon of cyanoacrilic acid. D1A is modified form of D1 which was obtained by adding a thiophene ring at 4th position of thiophene bridge.
The structure of D2 is derived from D1, it contains carbazole dendritic as donor and cyanoacrylic acid as acceptor, with the difference of π-spacer in such a way that D2 containsan oxadiazole ring substituted in place of 2nd thiophene ring.D2A is modified form of D2 which was obtained by adding a thiophene ring at 4thposition in π-spacer.
The structure of D3 is derived from D1 by adding an oxadiazole ring at 4th position of thiophene bridge of π-spacer. D3A is modified form of D3 which was obtained by adding an extra thiophene ring at 4th position and oxadiazole at 5th position in the π-spacer.