Thermally Stable Imines as New Potential Nonlinear Optical Materials

In the search for new thermostable acentric nonlinear optical (NLO) crystalline materials, several
polar imine derivatives with the general structure D-π-A(D‘) were synthesized and studied. Introduction of the amino
group (D‘) into the acceptor moiety of these molecules was supposed to bring hydrogen bonds into the crystal
structures, and so to elevate their melting points and to assist acentric molecular packings. Ten compounds of this
type have been prepared, and for six of them single crystals have been grown and characterized by X-ray diffraction
analysis. High melting points were found for all synthesized compounds. It was found that four compounds have
acentric crystal structures. Analysis of the crystal packing and hydrogen bonding in the compounds studied has
been carried out along with quantum calculations of the molecular NLO responses. This allowed an understanding
of the thermal stability of the compounds studied and some of their NLO characteristics.