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.