Synthesis and molecular properties of isomeric thienoisoindigo

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 9; no. 38; pp. 13218 - 13225
• Main Authors: Wang, Hua-Chun, Wang, Chang-Cheng, Chen, Yaorong, Cao, Jian, Ren, Xiancheng, Hong, Wenjing, Xu, Yun-Xiang
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 07.10.2021
• Subjects: Amides; Chemical synthesis; Conjugation; Fluorescence; Isomers; Molecular properties; Transport properties
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/d1tc02948g

Three isomers of thienoisoindigo (TII) are prepared by changing the ring-fusion mode or the amide arrangement of lactam units, namely, 5,10-dihexyl-5,10-dihydrodithieno[3,2- c :3′,2′- h ][2,6]naphthyridine-4,9-dione (TVTDA), 4,10-dihexyldithieno[3,2- c :3′,2′- h ][1,6]naphthyridine-5,9(4 H ,10 H )-dione (isoTVTDA) and ( Z )-4-hexyl-6-(5-hexyl-4-oxo-4,5-dihydro-6 H -thieno[2,3- c ]pyrrol-6-ylidene)-4,6-dihydro-5 H -thieno[3,2- b ]pyrrol-5-one (isoTII). The differences in electronic structures are validated through theoretical calculations and photophysical and electrochemical analyses. It is found that both six-membered lactams (TVTDA and isoTVTDA) show strong fluorescence. By contrast, both five-membered lactams (TII and isoTII) show almost no fluorescence due to non-radiative deactivation through conical intersection. Then, thioanisole was selected as an anchoring group to estimate the charge-transport properties of the four isomers. Compared with lactams in a head-to-tail arrangement, lactams in a tail-to-tail arrangement have a greater conductance due to higher conjugation and bigger transmission probability. As a conclusion, variation of the amide arrangement of lactam units can significantly regulate the single-molecule conductance. The luminescence and single-molecule conductance of the lactam molecules can be effectively regulated by changing the ring-fusion mode and the amide arrangement of lactam units.