Syntheses, crystal structures, and quadratic nonlinear optical properties in four “push–pull” diorganotin derivatives

Four “push–pull” diorganotin compounds obtained by reaction of methoxysalicylaldehyde or 4-diethylaminosalicylaldehyde, 2-amino-5-nitrophenol and dibutyltin or diphenyltin oxide are reported. The molecular structures for the diphenyl derivatives, in the solid state, show a tin in a distorted trigonal bipyramid geometry with the oxygen atoms in axial positions and the organic moieties and iminic nitrogen in equatorial ones. For the dibutyl derivative, a dimeric structure was favored due to intermolecular interactions between the tin and oxygen atoms, in this case, the tin atom shows a distorted octahedral geometry. A computational study of the diethyl derivatives constructed from the available dibutyl structure, at DFT level, revealed that the main differences between the solid and gas phases are the geometry around the tin atom and the π-conjugated organic backbone which is nearly planar in the solid state and distorted in the gas phase. The electric field induced second-harmonic (EFISH) of the nonlinear optical (NLO) response for the dibutyl derivatives revealed that the change from boron to tin increases 1.5 times the hyperpolarizabilities (β).