Some benzoate complexes of rare earth elements with the general formula [Nd2(Benz)6].3H2O
[Ln2(Benz)6].H2O (Ln: Sm, Eu) and [Gd2(Benz)6] (Benz: Benzoate) have been prepared. The ion fragments and luminescence properties of complexes in solid state were investigated by measuring the mass, excitation and emission spectra, the intramolecular ligand-to-rare earth energy transfer mechanisms were discussed. The mass spectra of complexes displayed complexes are dimes and there are six ion fragments in vapour. The emission spectra of the Nd(III) and Gd(III) complexes displayed only one narrow band arising from4 4 3/2 9/2 F I and 6 8 7/2 7/2 P S respectively. The emission spectrum of the Eu (III) complex displayed five bands arising from 5 7 0 1 D F , 5 7 0 2 D F , 5 7 0 3 D F , 5 7 0 4 D F ,5 7 0 5 D F transitions
On the other hand the emission spectrum of the Sm (III) complex displayed five bands arising from4 6 7/2 5/2 F H , 4 6 5/2 5/2 G H , 4 6 5/2 7/2 G H , 4 6 5/2 9/2 G H , 4 6 5/2 11/2 G H transitions.Keywords: complex, rare earth, benzoic acid, o-phenantroline.