Two kinds of trivalent thulium ion complexes used for organic electroluminescent devices have been synthesized.IR emission spectrum from a bilayer structure device utilizing Tin complexes as emitting materials has been observed for the first time.It is clearly to draw the conclusion that the IR emission is ascribed to the electronic transition from

3

H

4

to

3

H

6

of Tm

3+

ion chelated by ligands which possess higher energy level of lowest excited triplet state than the upper level

3

H

4

.Intramolecular energy transfer should take place from ligands to central ion because of the absence of direct absorption of Tm

3+

ion.