Design of non-linear optical materials based on inorganic compounds
This Thesis is concerned with the prediction, synthesis, characterization and testing of inorganic materials for Second Harmonic Generation (SHG). Chapter One describes the fundamentals of non-linear optics, and poses the problems, and some of their solutions which confront the synthetic chemist and the theoretical prediction of the second order hyperpolarizability constant β using CNDOVSB calculations. Chapter Two describes the design, implementation and calibration of an apparatus for measurements of the second harmonic generating efficiency of solids based on the Kurtz powder technique, and a solvatochromic method for the determination of β. Novel compounds with potential chirality due to atropisomerism, asymmetric octahedral structures, and asymmetric tetrahedral symmetry of metal centers are discussed in Chapters Three to Five. Chapter Three surveys the use of pentane-2,4-dionato- ligands and their coordination compounds as possible NLO active materials. The single crystal X-ray structures of bis(triphenylphosphine)(4-nitrobenzoylacetonato)palladium(II) tetrafluoroborate and tris(triphenylphosphine)[3-(2,4-dinitrophenyl)-pentane-2,4-dionato]palladium(II) tetrafluoroborate were determined. Chapter Four describes the syntheses, characterization and SHG properties of trans-β-ionylidenecyanoacetic acid (2-cyano-3-methyl-5-(2,6,6-trimethyl-l-cyclohexen-1- yl)-2,4-pentadienoic acid) and some of its metal and non-metal salts. Chapter Five describes the synthesis, characterization and second harmonic generation properties of some platinum(II) and palladium(II) complexes of β- ionylidenecyanoacetic acid. Chapter Six describes the use of conventional asymmetric carbon centers to introduce chirality into centrosymmetric compounds. The chiral compound (L)-N-[2-cyano- 3-methyl-5-(2,6,6-trimethyl-1 -cyclohexene-1 -yl)-2,4-pentadiene-1 -one]-L-proline and some of its salts were synthesized from β-ionylidenecyanoaeetic acid and tested for SHG.