Synthesis of yellow emitting bis-pyrimidine based purely organic phosphors

Two organic phosphors 5,5'-(4-pyridinylmethylene)bis[1,3-dimethyl-2,4,6- (1H,3H,5H)-pyrimidinetrione] (BP) and 5,5'-(4-nitrophenylmethylene)bis[1,3- dimethyl-2,4,6-(1H,3H,5H)-pyrimidinetrione] (BP-NO₂) have been synthesized through a one pot reaction of N,N-dimethylbarbituric acid and pyridine aldehyde in acetonitrile at 80 C. The synthesized phosphors were characterized by single-crystal X-ray crystallography, Fourier transform infrared spectroscopy, UV-vis spectroscopy, thermogravimetry analysis and photoluminescence (PL) spectroscopy. A broadband PL emission spectrum ranging from 400 to 800 nm was recorded from both phosphors. The BP showed a luminescence peak at ca. 560 nm (2.21 eV), while the BP-NO₂ exhibited a peak at 590 nm (2.1 eV), which reflect pure yellow emissions. The optimized geometry of the phosphors has been studied with a quantum chemical approach using the density functional theory. The highest occupied and lowest unoccupied molecular orbitals are predicted from the calculations.