Synthesis of new napthocarbazoles for use in organic transistors

Abstract

New organic molecules to be tested for use in organic field effect transistors were synthesised and characterised. 2-(9H-carbazole-3-carbonyl)benzoic acid, 5H-naphtho[2,3-b]carbazole-7,12-dione, 9-dodecyl-9H-carbazole, 2-(9-dodecyl-9H-carbazole-3-carbonyl)benzoic acid and 5-dodecyl-5H-naphtho[2,3-b]carbazole-7,12-dione were synthesised. 2-(9H-carbazole-3-carbonyl)benzoic acid and 2-(9-dodecyl-9H-carbazole-3-carbonyl)benzoic acid were first synthesised by Friedel-Crafts reaction of carbazole and 9-dodecyl-9H-carbazole, respectively, with phthalic anhydride. For this reaction, BF3 was first tried as a catalyst, followed by AlCl3, which proved to be more successful. 5-dodecyl-5H-naphtho[2,3-b]carbazole-7,12-dione synthesis showed greater success than the 5H-naphtho[2,3-b]carbazole-7,12-dione, possibly due to the enhanced solubility of the former from the addition of a 12-C alkyl chain to the carbazole core.

The compounds were characterised using NMR and mass spectrometry, with FTIR also being used in cases where the former two prove inconclusive. One further step is also necessary to obtain the target molecules 5H-naphtho[2,3-b]carbazole and 5-dodecyl-5H-naphtho[2,3-b]carbazole, which is the facile reduction of 5H-naphtho[2,3-b]carbazole-7,12-dione and 5-dodecyl-5H-naphtho[2,3-b]carbazole-7,12-dione using LiAlH4. These reactions were not complete due to time limitations and the low yield of the preceding reactions producing insufficient material to work with.