CHEM01200604004 Shri Sanyasinaidu Boddu - Homi Bhabha ...

these platinum complexes have been reported [22, 23]. Europium and terbium complexes
with ligands like 2-thenoyltrifluoroacetone (tta), bis(ferrocenyl-ethynyl)-1,10-phenanthroline
(Fc 2 phen), 6,6,7,7,8,8,8-heptafluoro-2,2-dimethyloctane-3,5-dione (fod) are well known
narrow band luminescent materials. In these materials, ligands act as sensitizers and absorb
light energy which is transferred to the metal ion. The latter, on de-excitation gives a narrow
band emission. Ligands based on β-diketones are well known sensitizers which can transfer
energy to lanthanide ions in β-diketone-lanthanide complexes. Several such complexes and
their luminescence properties have been reviewed recently [24-28]. More than 80% quantum
yield has been reported for some of these complexes after incorporation in polymers [29, 30].
A few representative examples of luminescent metal complexes are given in Fig.5 [31].
Fig.5.Examples of metal complexes [Alq 3 ( 1 π−π ∗ ), Eu(tta) 3 phen(f-f), PtOEP( 3 π−π ∗ ),
Ir(ppy) 3 ( 3 MLCT)] which shows intense photoluminescence [31].
1.5 Lanthanides and their Luminescence: Lanthanides are silvery-white, relatively soft,
reactive metals. It took more than 160 years until all of them were discovered, starting from
1787 when C.A. Arrhenius found a black stone near Ytterby (Sweden) from which several
lanthanides could be isolated [32]. It became apparent that the dominant oxidation state of
the lanthanides is +3 and the electronic configuration of a trivalent lanthanide ion can be
represented as [Xe]4f n [33]. Their popularity in modern technology is due to their exceptional
luminescence and magnetic properties. The 4f electrons are shielded by the 5s and 5p outer
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