title: Synthesis, crystal structures, and nonlinear optical (NLO) properties of new Schiff-base nickel(II) complexes. Toward a new type of molecular switch?
abstract: An H2L Schiff-base ligand that was obtained from the monocondensation of diaminomaleonitrile and 4-(diethylamino)salicylaldehyde is reported together with four related nickel(II) complexes formulated as [Ni(L)(L')] (L' = MePhCHNH2, iPrNH2, Py, and PPh3). Crystal structures have been solved for H2L, [Ni(L)(MePhCHNH2)], and [Ni(L)(iPrNH2)]. Surprisingly, the complexation process leads to the formation of a rather unusual nickel amido (-NH-Ni(II)) bond by deprotonation of the primary amine of H2L. A reduction of the quadratic hyperpolarizability (beta) from 38 x 10(-30) to 17.5 x 10(-30) cm5 esu(-1) is evidenced on H2L upon metal complexation by the electric-field-induced second-harmonic (EFISH) technique. Qualitative ZINDO/SCI quantum chemical calculations indicate that, in [Ni(L)(MePhCHNH2)], the beta orientation strongly depends on the laser wavelength. In particular, a beta rotation strictly equal to 90 degrees could be obtained with 1.022 microm incident light on passing from [Ni(L)(MePhCHNH2] to a hypothetical [Ni(HL)(MePhCHNH2]+ protonated complex, thus raising the possibility for a new type of molecular switch.
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, 31077 Toulouse, France.
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Costes
authors.forename: Jean François
authors.initials: JF
authors.lastname: Lamère
authors.forename: Christine
authors.initials: C
authors.lastname: Lepetit
authors.forename: Pascal G
authors.initials: PG
authors.lastname: Lacroix
authors.forename: Françoise
authors.initials: F
authors.lastname: Dahan
authors.forename: Keitaro
authors.initials: K
authors.lastname: Nakatani