Molecular Design Of Transparent UV-NIR Absorption Materials Based On The Benzobis(Thiadiazole): A Theoretical Study

The ongoing interest in organic transparent materials is driven by the scientificchallenges，they present as well as by the promise of real-world applications in a multitude ofproducts. Both strong ultraviolet (UV) and near infrared (NIR) absorption are importantphenomena. However, previous reports pay mainly attention to transparent materialspossessing either UV or NIR absorption. The transparent materials possess both UV and NIRabsorption have not been reported to our best knowledge.The investigation in the thesis departs into two parts:In this work, firstly, we explore the theoretical understanding for the origin of observedabsorption spectra of BBT derivatives here to confirm the deduction obtained experimentally.The calculated results reveal that M062X/6-31G(d)//PBE1PBE/6-31G(d) yield reliable resultsfor geometries and electronic properties of BBT derivatives. Meanwhile, introducing suitablespacer in the BBT derivatives as a bridge between D and A fragments will show completelycoplanar structure.Secondly, in order to design UV-NIR-absorbing organic materials, a series of moleculesare designed by linking the triphenylamine (R1),4,4-di-methane-4H-cyclopenta[2,1-b:3,4-b′]bithiophene derivative (R2), and fluorine (R3) to the core4,8-di(2-pyrrolyl)benzo[1,2-c:4,5-c’]-bis[1,2,5]thiadiazole (Py-BBT) at either α or β positions of the pyrrole fragment, denoted asna and nb series. Furthermore, we undertake the task of systematic investigations of thedifferent positions of the substituent effect on these properties of the Py-BBT derivatives viaquantum chemical calculations. The electronic structures of these designed molecules havebeen studied with emphasis on the frontier molecular orbitals, energy gaps, reorganizationenergies, mobilities, as well as absorption spectra. We will provide an in-depth understandingof the optical and electronic properties of these complexes and offer some directions forfuture research. These photo-electronic properties can be tuned by chemical modifcations ofthe donor fragments and the substitution positions on the Py-BBT fragment. The integrationof nb series strongly improves the optical properties of the dyes in terms of hyperchromicshift compared with na series, and shows high transparent in the visible region. Such strongabsorption in the UV and NIR region and transparency of the solar spectrum is unusual fororganic conjugated small molecules, which suggests that nb series molecules be promisingcandidates for practical applications.