Push-pull derivatives based on CF₃-substituted pyrimidines as solvatofluorochromic materials for OLEDs

A series of push-pull fluorophores based on CF₃-substituted pyrimidines was synthesized and investigated using spectroscopic measurements and quantum chemical calculations. First-generation OLEDs were fabricated using these push-pull systems as emitters, exhibiting emission maxima in the blue region (464-477 nm) and varying performance. The compounds exhibited strong positive solvatofluorochromism. TD-DFT calculations at the MN15/6-31G(d,p) level of theory revealed the rotational flexibility of the dimethylamino group in these systems. The wavelength and oscillator strength of the S₀ → S₁ transition in push-pull fluorophores are highly sensitive to the rotation of the dimethylamino group. Due to the rotational flexibility of the dimethylamino group, the observed spectral and luminescent properties likely arise from a combination of different conformations and are affected by environmental conditions.