Synthesis and Physical Properties of Benzopyridazine-Based Conjugated Molecules

A series of novel organic conjugated molecules （5a--5d） comprising 2,3-benzopyridiazine as electron-with- drawing core and thiophene derivatives as electron-donating arms have been synthesized successfully in good yields. The ultraviolet-visible （UV-Vis） absorption spectra and fluorescence spectra of 5a--5d revealed that the optical properties are strongly influenced by the interactions between nitrogen and sulfur atoms in the conjugated backbone, as well as the position of the alkyl chains in the thiophene rings. The experimental results and theoretical calculation data clearly indicated that the band gap and the energy levels of LUMO and HOMO could be fine-tuned by the po- sition of alkyl chains in the thiophene rings. Thus, the structure-property correlation of this class of conjugated molecules can be well established.