We report on the comprehension of novel europium activated hybrid organic Eu(dmh) phen (Eu: europium, dmh: 2,6-dimethyl-3,5-heptanedione, phen: 1,10 phenanthroline) organo-metallic complexes, synthesized at different pH values by the solution technique. Photo physical properties of these complexes in various basic and acidic solvents were probed by UV-vis optical absorption and photoluminescence (PL) spectra. Minute differences in optical absorption peaks with variable optical densities were encountered with the variation in solvent from basic (chloroform, toluene, tetrahydrofuran) to acidic (acetic acid) media, revealing bathochromic shift in the absorption peaks. The PL spectra of the complex in various acidic and basic organic solvents revealed the position of the emission peak at 613 nm irrespective of the changes in solvents whereas the excitation spectrum almost matched with that of the UV-vis absorption data. The optical density was found to be maximum for the complex with pH 7.0 whereas it gradually decreased when pH was lowered to 6.0 or raised to 8.0 at an interval of 0.5, demonstrating its pH sensitive nature. Several spectroscopic parameters related to probability of transition such as absorbance A(λ), Napierian absorption coefficient α(λ), molecular absorption cross-section σ(λ), radiative lifetime (τ ) and oscillator strength (f) were calculated from UV-vis spectra. The relative intensity ratio (R-ratio), calculated from the emission spectra was found to be almost the same in all the organic solvents. The optical energy gap, calculated for the designed complexes were found to be well in accordance with the ideal acceptance value of energy gap of the emissive materials used for fabrication of red organic light-emitting diode (OLED). The relation between Stoke's shift and solvent polarity function was established by Lippert-Mataga plot. This remarkable independence of the electronic absorption spectra of Eu complexes on the nature of the solvent with unique emission wavelength furnishes its potential to serve as a red light emitter for solution processed OLEDs, display panels and solid-state lighting.
We report the design and synthesis of volatile europium β-diketonate Eu(dmh) 3 phen organic hybrid complex by precipitation technique. A series of complexes were synthesized for different pH values, ranging between 8.0 and 6.0 maintaining stoichiometric ratio. Among all the synthesized complexes, Eu(dmh) 3 phen with pH 7 exhibits red intense emission at 613 nm with a sharp spectral bandwidth of 5 nm when excited at a wavelength of 372nm,infering that the synthesized complex is pH sensitive. This complex is further assessed for structural, thermal and luminescence behavior in various solvents. X-ray diffractogram reveals its crystalline nature and FTIR confirms the complete formation of the complex revealing the presence of TTA and bipy structure in the metal complex. TGA/DTA exhibits good thermal stability, which is highly essential for fabricating organic light emitting diodes (OLEDs) for solid state lighting. Hypsochromic shift was observed in the optical absorption spectra of Eu(dmh) 3 phen, when the solvent is changed from basic to acidic media.
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