Synthesis and Characterization of Two-Photon Active Chromophores Based on Tetrathienoacene (TTA) and Dithienothiophene (DTT)

Three new donor-π-donor (D-π-D) tetrathienoacene (thieno[2′,3′:4,5]thieno[3,2-b]thieno[2,3-d]thiophene (TTA))-cored chromophores, end-functionalized with electron-donating triphenylamine (TPA) groups, were developed and characterized for their two-photon-related properties by using both nano- and femtosecond laser pulses as the probing tools. TTA-based chromophores exhibit stronger and more widely dispersed two-photon absorption (2PA) than those of dithienothiophene (DTT)-based congeners. As a consequence, the bithiophene-conjugated TTA chromophore exhibits the highest maximum 2PA cross-section value (up to 2500 GM) with good thermal stability, and thus, it is the best performing two-photon chromophore among the studied model compounds. The bithiophene-conjugated DTT analogue exhibits the second highest maximum two-photon absorptivity of 1950 GM, which is nearly 7 times larger than that of previously reported DTT-based chromophores.