One- and two-photon induced emission in heterobimetallic Zn super(II)-Sm super(III) and Zn super(II)-Tb super(III) complexes with a side-off compartmental ligand

Heterobimetallic [Zn super(II)Ln super(III)] complexes have been obtained using a compartmental Schiff-base ligand, H sub(2)valdmpn, resulting from the 2 : 1 condensation between o-vanillin and 2,2-dimethyl-propilenediamine: [Zn(H sub(2)O)(valdmpn)Sm(O sub(2)NO) sub(3)] 1, [Zn(H sub(2)O)(valdmpn)Tb(O sub(2)NO) sub(3)] 2a, [Zn(H sub(2)O)(valdmpn)Tb(O sub(2)NO) sub(3)].H sub(2)O 2b, and [Zn(H sub(2)O)(valdmpn)Gd(O sub(2)NO) sub(3)].H sub(2)O 3. The crystal structures of 1, 2b, and 3 have been solved. Compounds 1 and 2a crystallize in a non-centrosymmetric space group (P2 sub(1)2 sub(1)2 sub(1)), being isomorphous. Crystals 2b and 3 are also isomorphous (space group P1&cmb.macr; ). The complex entities in the four crystals are similar and their structures consist of binuclear species with the pentacoordinated zinc(ii) ion hosted into the N sub(2)O sub(2) compartment and the lanthanide(iii) ion in the large, open compartment, with a coordination number of 10. The photophysical properties of the four compounds have been investigated. Strong visible excited (excitation tails extend up to 420-430 nm) one photon antenna sensitization was obtained with the samarium(iii) and terbium(iii) derivatives. Following femtosecond Ti:Sapphire laser at lambda sub(ex) = 775 nm, both second-harmonic generation at lambda sub(em) = 775/2 nm and two-photon induced emission in the VIS range were obtained, extending thus the excitation range of these complexes from the VIS to the NIR spectral range. The two-photon induced emission and second harmonic generation effect for a samarium(iii) complex are reported for the first time.