title: Non-centrosymmetric crystals of new N-benzylideneaniline derivatives as potential materials for non-linear optics.
abstract: Three new N-benzylideneaniline derivatives [p-nitrobenzylidene-p-phenylamineaniline (I), 2,4-dinitrobenzylidene-p-phenylamineaniline (II) and p-dinitrobenzylidene-p-diethylamineaniline (III)] containing electron-push-pull groups have been prepared. They present a planar N-benzylideneaniline core and neighbouring functional atoms, which are related through an efficient intramolecular charge transfer (CT). Two of the derivatives crystallize in non-centrosymmetric space groups, a necessary condition for non-linear optical (NLO) responses. The NLO properties were calculated for the molecular conformations determined by single-crystal X-ray diffraction as well as for the four molecules packed into each corresponding unit cell, using a quantum-chemical method at the cam-B3LYP/NLO-V level of theory. As expected from antiparallel face-to-face stacking through centrosymmetry, the main NLO descriptors - namely, the first hyperpolarizability (βtot) and its projection on the dipole moment direction (βvec) - are almost zero for the tetramer of derivative III. Interestingly, the calculated first hyperpolarizability decreases in the non-centrosymmetric unit-cell content of derivative II when compared to its single molecule, which may be related to its molecular pillaring, similar to that observed in derivative III. On the other hand, a desirable magnification of the NLO properties was found for packed units of derivative I, which may be a consequence of its parallel face-to-tail stacking with the CT vectors of all molecules pointing in the same direction. Moreover, the CT vector of compound I makes an angle of θ = 33.6° with its crystal polar axis, resulting in a higher-order parameter (cos(3)θ = 0.6) compared with the other derivatives. This is in line with the higher macroscopic second-order NLO response predicted for derivative I, βtot = 120.4 × 10(-30) e.s.u.
authors.affiliation: Instituto de Química, Universidade Federal de Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas, Minas Gerais 37130-000, Brazil.
authors.forename: Talita Evelyn
authors.initials: TE
authors.lastname: Souza
authors.affiliation: Instituto de Química, Universidade Federal de Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas, Minas Gerais 37130-000, Brazil.
authors.forename: Iara Maria Landre
authors.initials: IM
authors.lastname: Rosa
authors.affiliation: Faculdade de Ciências de Bauru, UNESP - Universidade Estadual Paulista, Campus Bauru, Av. Eng. Luiz Edmundo Carrijo Coube No. 14-01, Bauru, São Paulo 17033-360, Brazil.
authors.forename: Alexandre Oliveira
authors.initials: AO
authors.lastname: Legendre
authors.affiliation: Departamento de Química, ICE, Universidade Federal de Juiz de Fora, Campus Universitário, Juiz de Fora, Minas de Gerais 36036-330, Brazil.
authors.forename: Diego
authors.initials: D
authors.lastname: Paschoal
authors.affiliation: Instituto de Física, Universidade Federal de Goiás, Campus Samambaia, CP 131, Goiânia, Goiás 74001-970, Brazil.
authors.forename: Lauro J Q
authors.initials: LJ
authors.lastname: Maia
authors.affiliation: Departamento de Química, ICE, Universidade Federal de Juiz de Fora, Campus Universitário, Juiz de Fora, Minas de Gerais 36036-330, Brazil.
authors.forename: Hélio F
authors.initials: HF
authors.lastname: Dos Santos
authors.affiliation: Instituto de Química, Universidade Federal de Goiás, Campus Samambaia, CP 131, Goiânia, Goiás 74001-970, Brazil.
authors.forename: Felipe Terra
authors.initials: FT
authors.lastname: Matins
authors.affiliation: Instituto de Química, Universidade Federal de Alfenas, Rua Gabriel Monteiro da Silva, 700, Alfenas, Minas Gerais 37130-000, Brazil.
authors.forename: Antonio Carlos
authors.initials: AC
authors.lastname: Doriguetto
keywords: N-benzylideneaniline derivatives; electron–push–pull; non-centrosymmetric crystals; non-linear optics