Photoluminescence properties of new dinuclear [Eu(μ2-OC2H5)(btfa)(NO3)(phen)]2phen and mononuclear Eu(TTA)3(Ph3PO)2 complexes

Abstract

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() (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.