Experimental and Theoretical Exploration of Aryl Substituent Effects on the Electronic Properties of Asymmetric 4,7-Di(thiophene-2-yl)-benzo[c][2,1,5]thiadiazole Compounds

Abstract

By introducing phenyl, 1-naphtyl, 2-thienyl, 2-furanyl and 3-pyridyl rings into 4,7-di(thiophene-2-yl)-benzo[c][2,1,5]thiadiazole structure 2, five new asymmetric derivatives were prepared. For these compounds, HOMO/LUMO and gap energy levels were estimated by UV-Vis and cyclic voltammetry experiments in aprotic solvents. The results showed significant effects of aryl groups on gap data, were this parameter was mainly tuned by changes in the HOMO level of structure 2. These properties were examined also by electronic structure calculations and the estimations obtained described the experimental trends. Quantum chemical modeling exhibited homogeneous distribution of HOMO and LUMO energy levels in all studied compounds and suggest that planarity in the system is crucial to diminish the gap. The calculations also explain that, a conformational change (predicting a 54.2° dihedral angle between the 1-naphtyl substituent and the rest of the molecule) was responsible for the unexpected increase in gap of compound bearing a 1-naphtyl substituent; the latter phenomenon was corroborated by X-Ray information, which reveals a dihedral angle of 46.8°.

Keywords:

• 4,7-Di(thiophene-2-yl)-benzo[c][2,1,5]thiadiazoles
• conformation analysis
• electronic structure
• substituent effects
• theoretical/experimental determinations

Acknowledgments

Authors thank DGTIC-UNAM for computational resources provided under project LANCAD-UNAM-DGTIC-022. The authors would like to thank the technical assistance provided by Gonzalez-Quezada M. (MS), Tapia-Mendoza E. (MS), Flores-Leonar M. (PhD), Romero-Avila M. (MS), García-Ruiz K. (MS), Rivera-Mendez L. (MS) and Vazquez-Sanchez A. (PhD), to Klain M. for spelling suggestions. For EA determinations authors thank to technician Lemus V. (USAII). We want to thank to CONACYT for the PhD grant extended to L.D.S.V. (273646). V.M.U.S thanks DGAPA for a PASPA national grant sabbatical stay.

Disclosure statement

The authors declare no relevant interest to disclose.

Additional information

Funding

This research was partially funded by CONACyT-SENER-Fondo de Sustentabilidad Energética under project 245754.