Synthesis and Optical Properties of Anion-Responsive X-shaped -Electronic System

The properties of donor-pi-acceptor molecules are strongly influenced by the electron density and configuration of both donor and acceptor moieties. In particular, X-shaped molecules, where two linear pi-conjugation systems ended by donors and/or acceptors are crossed in their middle, are well-known to separate frontier molecular orbitals, and the donor and acceptor strongly influence the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), respectively. A novel X-shaped molecule, containing a diphenylamino group as the donor and a dimesitylboryl group as the acceptor, was synthesized to modulate the optical properties via anion complex formation. The X-shaped molecule formed [1+1]- and [1+2]-type anion complexes in solution, and a negative cooperative effect for the formation of the [1+2]-type anion complex was observed. UV-vis and fluorescence spectroscopy reveled the changes in the optical properties by the formation of anion complexes, with the spectral changes upon anion addition were consistent with the theoretical spectra obtained from time-dependent density functional theory calculations. Furthermore, the X-shaped molecule, which exhibits remarkable luminescence properties even in the solid state, demonstrated electroluminescent behavior.