4-(Diethylamino)salicylaldehyde-based twin compounds as NLO-active materials

• 4-(Diethylamino)salicylaldehyde-based twin compounds were synthesized.
• Their glass transition temperatures range from 79 to 103 °C.
• The solutions show Stokes shifts ranging from 114 to 214 nm.
• High nonlinear optical activities with d33 values in the range of 24.5–31.9 pm/V.

4-(Diethylamino)salicylaldehyde-based twin compounds containing 1,3-indandione and 1,3-bisdicianovinylindane moieties were synthesized and their thermal, optical, photophysical, electrochemical, photoelectrical and nonlinear optical properties were studied. The synthesized compounds form glasses with the glass transition temperatures ranging from 79 to 103 °C. Photoluminescence spectra of the solutions of compounds exhibited red-shifts with the increase of the solvent polarity that was caused by the positive solvatochromic effect. The linear dependencies between the position of the photoluminescence maxima of compounds and the empirical parameter ET(30) of the different solvents were observed. The electron photoemission spectra of thin layers of the synthesized materials showed ionization potentials of 5.34–5.52 eV. The nonlinear optical properties of corona poled molecular glasses were characterized by means of Maker fringe technique. Three compounds exhibit remarkable nonlinear optical activities with d33 values in the range of 24.5–31.9 pm/V.