The synthesis and spectroscopic studies of two novel halogen pyrazoloquinoxaline (PQX) derivatives with 6-substituted fluorine (FPQX) or chlorine (ClPQX) are reported. The optical absorption and fluorescence emission spectra of both dyes are recorded in cyclohexane, tetrahydrofuran and acetonitrile solutions. The spectroscopic characteristics and photophysical constants derived from these measurements provide characterization of FPQX and ClPQX dyes as potential fluorescence emitters for luminescence or electroluminescence applications. Measured optical absorption and fluorescence emission spectra are compared with the results of quantum-chemical calculations based on DFT/TDDFT methods with hybrid B3LYP or long range corrected (LRC)-BLYP exchange-correlation (xc) functionals and polarizable continuum model. The reparameterized LRC-BLYP functional (ω = 0.231 Bohr−1) provides considerably better description of the experimental spectra comparing to the method based on the hybrid B3LYP functional. Discrepancy between the experiment and theory may be additionally reduced assuming that the planar molecular conformation, which results in most cases from geometrical optimization both in ground or excited states (T=0K), indeed may be broken at T≫0K due to rotation of thermally activated phenyl rings singly bonded to PQX moiety. In relevant approach we assume that the optical absorption statistically takes place from preferably weakly twisted ground state molecular conformations. The fluorescence emission, in contrast, would be expected from more twisted excited state molecular conformations.