Synthesis, structural investigation and NLO properties of three 1,2,4-triazole Schiff bases

We report in this work the synthesis, crystal structures analyses, and nonlinear-optical (NLO) properties of three Schiff bases with halogens and triazole moieties: (E)-1-(4-bromophenyl)-N-(1H-1,2,4-triazol-3yl)methanimine L1, (E)-1-(4-bromophenyl)-N-(4H-1,2,4-triazol-3-yl)methanimine L2, and (E)-1-(4chlorophenyl)-N-(4H-1,2,4-triazol-3-yl)methanimine L3. The three molecules are built on the basis of the same backbone formed by two aromatic rings (phenyl and triazole) linked by imine bridge. The two first compounds L1 and L2 contain tautomers of the Schiff base, where a phenyl ring is substituted by a bromine atom. The third one, L3, is similar to L2 but contains a chlorine atom instead of bromine. In crystals formed by these three Schiff bases the three dimensional networks are formed by supramolecular interactions such as hydrogen bonds, C-X...pi and X...X (X = Cl or Br) contacts. Complementary Hirshfeld surface analyses were carried out to investigate and quantify the contributions of the different intermolecular interactions within the supramolecular assemblies. These analyses reveal that the main contributions in the studied compounds are provided by the H center dot center dot center dot H and N center dot center dot center dot H interactions that represent-53% (for L1),-49% (for L2) and-50% (for L3) of the total contributions to the Hirshfeld surface. The nonlinear optical properties are investigated by nonlinear diffuse femtosecond-pulse reflectometry and are compared with those of the reference material LiNbO3, in particular regarding the temporal evolution. (C) 2020 Elsevier B.V. All rights reserved.