Controlling photophysical properties is critical for the continued development of electroluminescent devices and luminescent materials. The preparation and study of novel molecules suitable as luminescent for the development of optoelectrical devices have recently received a lot of attention. Even though the as-triazine unit is a good building block for organic active substances, it is rarely used in this context. We created here novel bis-triazine derivative dyes in the far UV–Vis range by alkylation of triazine-thione derivatives with appropriate dibromo compounds. At the B3LYP/6-311**G(d,p) basis set, their optimal molecular structures were obtained. DFT technique confirmed that the new triazine derivatives are in noncoplanar with one of the two phenyl rings and the triazine plane rotating out by 102.09. Also, depending on the energy gap difference between HOMO and LUMO, some important parameters including chemical potential (π), electronegativity (χ), and chemical hardness (η) were calculated. The compounds may be readily polarized and have significant NLO characteristics, as seen by the tiny HOMO–LUMO energy gap. The calculated values for the polarizability (α) of the two new triazine derivatives have the range 6.09–10.75 × 10–24 (esu). The emission peaks seemed to move to the long-wavelength (redshift), with a rise in the fluorescence band, suggesting that the singlet excited state is more polar than the ground state. The influence of solvent polarity and the intermolecular charge transfer (ICT) processes are reflected in the photophysical properties of new fused triazine derivatives. These properties such as extinction coefficient, absorption and emission cross-sections, fluorescence quantum yield, fluorescence lifetime, oscillator strength, the dipole moment, radiative decay rate constant, the energy yield of fluorescence, and the attenuation length were assessed and discussed.

Polymethylmethacrylate (PMMA) and Rhodamine 6G (R6G), were used to achieve an electronically excited R6G/PMMA complex of definite stoichiometry as an active laser exciplex, pumped by different laser sources. This paper is the first that is capable of interpretation of the interactions of the reactants to form the exciplex on the molecular level using DFT. The system was prepared by thermochemical polymerization, and structurally identified using FTIR, XRD and SEM in conjunction with DSC. In low-to moderate-loading of R6G, FTIR and XRD studies indicated a good interaction between PMMA and R6G to give poor-or semi-crystalline structures. Higher dye loadings were achieved for the synthesized exciplex; loading of PMMA with 0.25 Wt-% R6G decreased the glass transition temperature from 98.74 °C to 70.08 °C. However, increasing the loading with R6G to 5 Wt-% and 20 Wt-% increased the Tg values to 86.26 and 91.90 °C, respectively. MD simulations were conducted; the electronic mobility within the system was related to different quantum parameters, EHOMO, ELUMO, η, μ and ω were about -7.671 eV, -5.241 eV, 1.215 eV, -6.456 eV and 17.1522 eV, respectively. DFT calculations indicated that R6G/PMMA has a characteristic lasing stability, so that the lasing lifetimes about 8000 pulses and efficiencies about 21% were obtained.