Novel D–π–A–π–D type pyrimidine-based dyes, possessing (hetero)aryl electron-donating groups in 2,4-positions were synthesized, and their photophysical properties were investigated by using absorption and emission spectral analyses. All dyes proved to exhibit a strong emission solvatochromism with quantum yields up to 0.96, depending on their molecular structure and solvent polarity. The compounds have been established to undergo a reversible protonation, directed at nitrogen atoms of the pyrimidine ring, and these phenomena are associated with dramatic color changes. In addition, fluorophores 5a-d show a high sensitive response for nitroaromatic traces in solutions or real-time detection of their vapors in air. These findings indicate that the compounds obtained can be regarded as excellent fluorophores for fluorescent material applications.