Synthesis and quadratic molecular hyperpolarizabilities of two new chiral boronates: Computational and experimental study Horacio Reyes a , Jose ´ Marı ´a Rivera a , Norberto Farfa ´n * ,a , Rosa Santillan a, * , Pascal G. Lacroix * ,b , Christine Lepetit b , Keitaro Nakatani c a Departamento de Quı ´mica, Centro de Investigacio ´ n y de Estudios Avanzados del IPN, Apdo. Postal 14-740, 07000 Me ´xico D.F., Mexico b Laboratoire de Chimie de Coordination du CNRS, 205 Route de Narbonne, 31077 Toulouse Cedex 04, France c Laboratoire de Photophysique et Photochimie Supramole ´culaires et Macromole ´culaires (UMR8531 du CNRS), Ecole Normale Supe ´ rieure de Cachan, Avenue du Pre ´sident Wilson, 94235 Cachan, France Received 18 March 2005; received in revised form 2 May 2005; accepted 3 May 2005 Available online 11 July 2005 Abstract A monomeric boronate and an oxobridged chiral dimer were obtained by reaction of the ligand derived from 4-diethylamino- salicylaldehyde with (R)-()-phenylglycinol, and phenyl boronic acid or boric acid. The compounds were fully characterized by spectroscopic techniques ( 1 H, 13 C, 11 B NMR, elemental analyses, IR and masses spectrometry); and their molecular hyperpolariz- abilities were investigated by the electric field induced second harmonic (EFISH) technique and semi-empirical calculations. The experimental quadratic hyperpolarizability which is equal to 9.8 · 10 30 cm 5 esu 1 at 1.064 lm for the monomeric derivative rises to 19.5 · 10 30 cm 5 esu 1 in the dimeric specie. Ó 2005 Elsevier B.V. All rights reserved. Keywords: NLO; Boronates; DFT and semi-empirical calculations 1. Introduction There is a considerable interest in the synthesis and characterization of organoboron compounds due to their interesting applications, for example in medicinal chemistry, as anticancer agents or in Boron Neutron Capture Therapy [1]. Moreover, they also display a wide range of applications in organic synthesis [2], as materi- als with fluorescence [3], electro-optical and nonlinear optical properties [4]. The design of nonlinear optical (NLO) materials efficient in second harmonic generation (SHG) is usually achieved in two steps which imply first the synthesis of compounds having large b values, according to the fol- lowing expression of the molecular polarization (l) in- duced by a laser electric field (E) [5]: lðEÞ¼ l 0 þ aE þ bE 2 þ ð1Þ In this expression, l 0 is the permanent dipole moment, a is the linear polarizability, and b the quadratic hyperpo- larizability, the origin of the NLO response. The largest b values are obtained when the molecules contain p-elec- tron systems with charge asymmetry arising from the use of donor and acceptor substituents [6]. Ultimately, the NLO response of a macroscopic material is related not only to b, but also to the relative orientation of mol- ecules in the solid state (second step). A non-centrosym- metric environment is required to avoid the cancellation of the quadratic property. In a previous study we reported on the quadratic NLO properties of a series of 18 ‘‘push-pull’’ boronates 0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2005.05.034 * Corresponding author. Tel.: +52 55 5061 3725; fax: +52 55 5061 3389. E-mail addresses: jfarfan@cinvestav.mx (N. Farfa ´n), rsantill@ cinvestav.mx (R. Santillan), pascal@lcc-toulouse.fr (P.G. Lacroix). Journal of Organometallic Chemistry 690 (2005) 3737–3745 www.elsevier.com/locate/jorganchem