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[Display omitted] • Two coumarin-based compounds with blue and green emission were prepared. • These compounds have the potential to be used as novel dual-state emitting luminogens. • Positive solvatochromism is found in these molecules. • These molecules exhibit Aggregation-Caused Red Shifted Emission. • Rewritable data storage has been demonstrated using the DSEgen molecule. The development of dual-state organic luminogens with high emission efficiency both in solution and solid phase is still a difficult task. Dual-state emissive fluorescent materials have proven to have a much broader application in several fields. Molecular design plays a significant role in fabricating switchable as well as tunable emissions. Nonetheless, the mechanism of dual-state emission needs to be studied further. Herein, two compounds, Blue-Yellow emissive material (BYEM) and Green-Red emissive material (GREM), have been designed and synthesized for a novel class of luminogens with dual-state emission (DSEgens) properties. These compounds emit luminously in solution state as well as solid state, with Aggregation Caused Red-Shifted Emission (ACRE) emission. Close-packed molecular structure and the steric hindrance effect can reduce the intramolecular rotation solution state, which accelerates the radiative transition of the compound in the solution state. On the contrary, in the solid state, the twisted structure and intermolecular C–H⋯π interactions can indorse the J -aggregation, which leads to the high fluorescence at the solid state. Significant red shift emission at solid state has been supported by theoretical calculations. On the other hand, by combining a partly shared donor–acceptor unit based on the twisted molecule, these compounds have shown good solvatochromic behavior. Gradual redshift emission has been observed as the solvent polarity is increased. These dual state highly emissive compounds can be applied in several industrial applications as well as the biomedical field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Red emissive complexes with [Eu(TFFB) 3 L] stoichiometry were synthesized and investigated by spectroscopic studies. • Red emissive behavior of the complexes was characterized by photoluminescence study. • Photophysical characteristics of the mononuclear Eu(III) complexes were analyzed theoretically (JOES) and experimentally. • Probability amplitude distribution and the energy of HOMO and LUMO were estimated through DFT. Heteroleptic trivalent complexes of europium were prepared on reaction of EuCl 3 ·6H 2 O, fluorinated 1,3-diketone and 2,2′-bipyridine or its derivatives in the molar ratio of 1:3:1 respectively. Structural analysis of prepared complexes was done via spectral study. Luminescence features of synthesized complexes have been explored by the photoluminescence and decay spectral profile. Strong emission in the red spectral region was observed for Eu3+ ion corresponding to the electric dipole 5D 0 → 7F 2 hypersensitive transition. The radiative transition probabilities as well as the Judd-Ofelt parameters were computed and discussed. Complexes emit red light in the visible spectrum as illustrated by their CIE color coordinates are essential for creating effective display and lighting devices. [ABSTRACT FROM AUTHOR]