First hyperpolarizability of some nonconjugated donor-acceptor 3D molecules: Noncentrosymmetric crystal through conformational flexibility

Four derivatives of 2,4,6-tris(benzylamino)-1,3,5-triazine are synthesized and detailed computational and nonlinear optical investigations are carried out. Computations indicate near degenerate conformations (C₃ and C ₁ symmetry) in all systems in the gas phase; the dipole moments are also of similar magnitude in all of them except molecule 4 [2,4,6-tris(4- fluorobenzylamino)-1,3,5-triazine]. HRS measurements of these molecules in solution reveal moderately large β values; structure-property relations are analyzed through computations. These molecules have one added advantage of nearly 100% optical transmission through the visible range, due to the nonconjugated structure. Molecule 4 crystallizes in a noncentrosymmetric structure by adopting the conformation with the lower dipole moment; it also shows optical SHG in the solid state.