Novel D-π-A molecules modulation: Towards high-performance second order nonlinear optical materials

• 1、Chemistry and Chemical Engineering School, Chongqing University, Chongqing 401331

Abstract：Push-pull chromophores with large hyperpolarizability, excellent electro-optical activity and strong stability are crucial for the development of efficient nonlinear optical (NLO) materials.In the present work, the electronic properties of some typical electron donors (D) and acceptors (A) and azulene moietyfunctionalized as a π-conjugated bridge (π)are studied.Optimal combination of D, π and A was designed according to the sum-over-states model and frontier molecular orbital matching for charge transfer.A series of novel D-π-A molecules with strong NLO responses were obtained by the introduction of azulene as π bridge.The electronic structures and second-order NLO properties of all molecules are predicted using (time-dependent) density functional theory combined withthe sum-over-states model.It is found thatazulene greatly enhances the NLO response by its moddification of the electronic structures such as the dipole moment, HOMO-LUMO gap, and transition energy of the molecules. For example, with the introduction of azulene, the static first hyperpolarizability <β0>of D7A4increases by nearly five times from ?12.09×10?30 esu per heavy atomto ?61.36×10?30 esu per heavy atom (D7BazA4).Azulene serves as not only a π-bridge but also a part of polar chromophore. The presetn work shedslight on future molecular NLO materials exploration.

Keywords： physicalchemistry nonlinear optics D-π-A model azulene intramolecular charge transfer the static first hyperpolarizability