Preparation, properties, and X-ray structures of bis(10-methyl-9- methyleneacridan)-type electron donors with a thiophene, bithiophene, or terthiophene skeleton: Redox switching of thiophenethienoquinoid structure accompanied by UVvisNIR electrochromic response

The newly designed title dyes 13 have a thiophene-type -skeleton, to which two methyleneacridan subunits are attached as electron-donating end groups. They undergo reversible one-wave 2e-oxidation to the corresponding dications containing a thienoquinoid moiety. The redox and spectral properties can be modified by changing the -skeleton, and bithiophene 2 and terthiophene 3 can serve as new entries of UVvisNIR electrochromic materials.