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

Heterobimetallic [Zn(II)Ln(II)I] complexes have been obtained using a compartmental Schiff-base ligand, H(2)valdmpn, resulting from the 2 : 1 condensation between o-vanillin and 2,2-dimethyl-propilenediamine: [Zn(H2O)(valdmpn)Sm(O2NO)(3)](1), [Zn(H2O)(valdmpn)Tb(O2NO)(3)] 2a, [Zn(H2O)(valdmpn)Tb(O2NO)(3)]center dot H2O 2b, and [Zn(H2O)(valdmpn)Gd(O2NO)(3)] center dot H2O 3. The crystal structures of 1, 2b, and 3 have been solved. Compounds 1 and 2a crystallize in a non-centrosymmetric space group (P2(1)2(1)2(1)), being isomorphous. Crystals 2b and 3 are also isomorphous (space group P (1) over bar). 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 N2O2 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(ex) = 775 nm, both second-harmonic generation at lambda(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.