Maintenance work is planned for Wednesday 18 August 2021 from 07:00 to 23:59 (BST). Pages may load more slowly than usual and you may not be able to access some content or log in. If this happens then please refresh your web browser or try waiting two to three minutes before trying again. Sorry for any inconvenience and thank you for your patience. You do not have JavaScript enabled. Please enable JavaScript to access the full features of the site or access our non-JavaScript page. 18 unprecedented tetrazines unsymmetrically substituted at C3 and C6 by an aromatic heterocycle have been successfully prepared by the S-induced reaction of aromatic nitriles with hydrazine hydrate under thermal conditions. The spectral property investigation suggests that compounds 4d, 4e, 4f, 4p, 4q, 4r, and 4v can display intense fluorescence in the visible region, and their fluorescent properties are affected by the substituents both in tetrazine and in phenyl rings. Moreover, the electrochemical behaviors of these synthesized tetrazines are demonstrated to be fully reversible. Furthermore, density functional theory (DFT) calculations for these compounds were performed to investigate their optimized structures, Fukui function and reactivity or selectivity in the inverse electron demand Diels–Alder reaction. Novel 3,6-unsymmetrically disubstituted-1,2,4,5-tetrazines: S-induced one-pot synthesis, properties and theoretical study To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content.