Synthesis And Characterization Of Benzopyridazine-based Conjugated Molecules

Organic semiconductors have been intensively investigated especially dueto their optoelectronic properties and potential applications in many fieldssuch as organic field effect transistors (OFETs), organic photovoltaics(OPVs), electrochromic devices, and organic light emitting diodes(OLEDs)[4]. The most critical challenges in developing above-mentioneddevices are to design and synthesis of novel hole-transportingsemiconductors(for p-type semiconductors) and electron-transportingsemiconductors(for n-type semiconductors)[1]. Great efforts have beenundertaken in the past decades to develop p-type organicsemiconductors[5]. However n-type organic semiconductors with asuitable electron affinity, excellent electron-transporting properties, andgood solubility in solvents, are still very few and undesirable enoughagainst oxidation in the process of the synthesis, device fabrication, andmeasurement.4Introduction of heteroatom to the conjugated backbone forthe formation of heteroacene, is an efficient method to achieving n-typeorganic semiconductors.5Recently, pyridazine derivatives containing twoelectron-withdrawing imine nitrogen atoms represent very interestingcandidate for n-type organic conjugated molecules, because of the electon-deficient character of the pyridazine.6,7With central-electronextended fragment, these compounds exhibited an inherent chargemobility used to be best suited electron transport device. But surprisingly,as far as we know, fused pyridazine derivatives are still not documented.Herein, we report the design and synthesis of a series of novel n-typeorganic conjugated oligomers comprising2,3-benzopyridiazine aselectron-withdrawing core and thiophene derivatives as electron-donating arms. On the other hand, the effect of the substituted alkyl chains atdifferent position of the thiophene ring, have been also taken into account.Meanwhile, optical and electrical properties of these molecules are alsosystematically investigated for elucidation of structure-propertycorrelation of these new conjugated oligomers.