STRUCTURE-ACTIVITY RELATIONSHIP OF NEW ORGANIC NLO MATERIALS BASED ONPUSH-PULL AZODYES - 1 - SYNTHESIS AND MOLECULAR-PROPERTIES OF THE DYES

Several new push-pull azobenzene dyes were synthesized by diazonium sa lt coupling of electron-poor anilines with N,N-dialkylanilines. Their dipole moments and first-order hyperpolarizabilities were evaluated re spectively from the concentration dependence of the dielectric constan t of solutions in apolar solvents and by the electric-field-induced-se cond-harmonic-generation (EFISH) technique. Investigation of the influ ence of both nature and steric hindrance of the electron with drawing group allowed to highlight a significant deviation from linearity in t he relationship between dipole moments and first-order hyperpolarizabi lities. This effect was particularly noticeable when multiple electron withdrawing groups pointing in different directions were present on t he same phenyl ring.