Novel helix-shape bis[1,2,4]triazolo[4,3-b:3′,4′-f][1,2,4,5]tetrazines: synthesis, optical and charge-transfer properties

A two-step route to a wide range of new derivatives of 1,8-disubstituted bis[1,2,4]triazolo[4,3-b:3,4-f][1,2,4,5]tetrazines starting with the readily available 3,6-dihydrazinyl-1,2,4,5-tetrazine and the corresponding aldehydes has been proposed. The developed method is convenient and transition metal-free. The basic optical, electrochemical and semiconductor properties of the resulting compounds have been studied. The synthesized bis[1,2,4]triazolo[4,3-b:3,4-f][1,2,4,5]tetrazines show weak luminescent properties in MeCN solution with the highest quantum yields within 21-23%; they have an unexpected quasi-reversible electroreduction peak and exhibit ambipolar semiconductor properties with charge carrier mobilities ranging from 10⁻⁴ to 10⁻⁶ cm² V⁻¹ s⁻¹. The DFT and TDDFT calculations have also been performed to explain the observed features.