Push–pull effect to improve the electronic and optical properties of [7] circulene.

In the present research, an electron donor‐acceptor (push‐pull) compound based on [7] circulene was studied using density functional theory (DFT) methods. The electron donor and acceptor units were attached to [7] circulene to improve optical properties. It was demonstrated that the band gap of [7]circulene molecule was lowered in electron donor and acceptor groups' presence, also the CN‐CIR7‐NHLi and CF3‐CIR7‐NHLi molecules have the lowest values of the band gap. It was observed that the optical properties of [7]circulene molecule was improved in the presence of electron donor and acceptor units. Between these units, the ‐CN and ‐CF3 as electron acceptors and ‐NHLi substituents as electron donor groups have higher enhancements on optical properties of circulene which is corresponding to the results obtained for energy gap values. The electric dipole moment (𝜇D) and the charge transfer, the electronic properties, polarizability (α), and first hyperpolarizability (β) values of the investigated molecules have been also computed. The results of this research may be useful in designing new materials applicable as improved photosensitizer and photodynamic therapy. All calculations and analyses are carried out by using DFT and dependent time DFT (TD‐DFT) with the B3LYP/6–311G (d,p) model in the Gaussian 09 software packages. [ABSTRACT FROM AUTHOR]