Speaker
Description
Following our interest in photoluminescence properties of lanthanide coordination polymers constructed using 2-nitro-1,4-benzenedicarboxylate (NO$_2$-BDC$^2$$^-$ [1,2], the lanthanum and its europium and terbium doped samples have been prepared; [(La)(NO$_2$-BDC)$_1$$_.$$_5$(H$_2$O)$_4$] (1),[(La$_0$$_.$$_9$$_2$Eu$_0$$_.$$_0$$_8$)(NO$_2$-BDC)$_3$(H$_2$O)$_4$] (2), [(La$_0$$_.$$_9$$_2$Tb$_0$$_.$$_0$$_8$)(NO$_2$-BDC)$_3$(H$_2$O)$_4$] (3). According to the powder x-ray diffraction, 1-3 are isostructural exhibiting a dense 3D framework structures. Photoluminescence of the three samples were investigated among which only blue emission due to the intra-ligand fluorescence was found for 1 with the excitation at 337 nm. The doped samples 2 and 3 emitted the characteristic fฟ-f transitions at the same excitation wavelength; $^5$D$_0$-$^7$F$_j$ (J = 1, 2, 3, 4) at 588, 617, 672 and 693 nm for 2, and $^5$D$_4$-$^7$F$_j$ (J = 6, 5, 4, 3) at 488, 545, 586 and 620 nm for 3. Temperature dependent photoluminescence properties of 2 (Eu$^I$$^I$$^I$; $^5$D$_0$-$^7$F$_2$) and 3 (Tb$^I$$^I$$^I$; $^5$D$_4$-$^7$F$_5$ ) have been investigated in term of intensity, revealing significant difference in the Eu$^I$$^I$$^I$ and Tb$^I$$^I$$^I$ centered emissions in 333(2)-393(2)K range. The observed thermal responsive f-f transitions of the doped samples is discussed.
