Reversible and pH dependent photophysical properties of mixed-ligand Ru(II) complexes containing 2,2′-bipyridine and nitrosobarbiturate: Experimental and theoretical approach

A ruthenium(II) complex of type [Ru(bpy)2(L′H)]·PF6 1 (L′H = 5-Nitroso-pyrimidine-2,4,6-trione, is prepared by the reaction of [1,5-dihydro-5-[5-pyrimidine-2,4(1H,3H)-dionyl]-2H-chromeno[2,3-d] pyrimidine-2,4(3H)-dione)]) LH4 with [Ru(bpy)2(NO3)2] (prepared in situ). It is characterized using elemental analyses, spectroscopic and single crystal X-ray diffraction techniques. This complex is converted in another complex of type [Ru(bpy)2(L′)] 2 by the addition of an aqueous solution of NaOH. The complex 2 turns back to complex 1 after its neutralization by the addition of an aqueous solution of HCl. The reversible conversion of complexes 1 and 2 in each other is monitored using their UV–Vis and luminescence spectra. Quantum chemical calculations using density functional theory (DFT) method corroborates transfer of electron density from nitrosobarbiturate to metal ion leading the formation of complex 2.