A new dinuclear complex Europium(III) bis[(μ2-ethoxy)(benzoyl trifluoroacetonato)(nitrate) (1,10-phenanthroline) europium(III)]2 1,10-phenanthroline, here after [Eu(μ2-OC2H5)(btfa)(NO3)(phen)]2·phen)(1) (Figure 1a) and the mononuclear complex Eu(TTA)3(Ph3PO)2(2) (Figure 2a) were synthesized and characterized by photoluminescence (PL) spectroscopy. The PL emission spectra of the powder samples of the compounds were recorded in the temperature range 10.7 – 300 K. Both complexes show rare metal-centered luminescence in the energy range characteristic of the Eu3+ ion (580 – 710 nm) with emission bands according to ion selection rule. The emission bands in the PL are attributed to the internal 4f → 4f radiative transitions of the Eu3+ ion 5D0 → 7Fi (i = 0→4) and, in addition, to the splitting of each level caused by the influence of the electric field of the ligands of the complex. Due to the splittings, each level is divided into 2i+1 sublevels, which are well observed in the mononuclear compound 2 centered at 580, 595, 615, 650, and 698 nm. However, in the PL spectrum of the dinuclear compound, the splits show a double number of splits (2(2i + 1)), which indicates the presence of two positions of the Eu3+ ion in the molecule and which are not optically equivalent.
A series of coordination organic compounds based on the trivalent Eu3+ ion were synthesized and optimized: Eu(o- MBA)3phen, Eu(DBM)3(Ph3PO)1·H2O and Eu(TTA)3(Ph3PO)2. The efficiency of the photoluminescence (PL) emission of these coordination compounds depend on preparation technology, specifically on the optimal choice of the ligands. The photoluminescence spectrum measured in the range 500 – 750 nm exhibits a number of narrow (atomic-like) emission bands with the FWHM less than 10 nm. These PL emission bands are attributed to optical transitions5D0 → 7Fj , j 0...4 in the 4f orbital of the, ion. PL experimental results were analyzed in the framework of Judd-Ofelt theory and the characteristic luminescence parameters were obtained: PL lifetime constant, quantum yield, Ω coefficient, the probability Ai jfor electric dipole transitions, etc.
A new coordinate organic compound (COC) Eu(DBM)3(Ph3PO)1H2O was synthesized and investigated (DBM stands for 1,3-Diphenyl-1,3-propanedione and Ph3PO for triphenylphosphine oxide). The size of obtained Eu(DBM)3(Ph3PO)1H2O powder nanocrystals is around 50 nm. Under ultraviolet light excitation, the material exhibits an abundant and pure red color photoluminescence (PL). The PL spectrum measured in the range of 500 - 750 nm has a number of narrow (atomic) emission lines with FWHM less than 10 nm, which are assigned to the energy transitions 5D0→7Fi (i = 0,1,2,3,4) in the 4f – shell of the Eu3+ ion. PL experimental results and its kinetics were analyzed using the theory of Judd-Ofelt's parametric method and the characteristic parameters were obtained: the lifetime τ, quantum efficiency η, and transitions probability of electrical dipoles Aij.
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