Thermally stable, highly nonlinear porphyrin-based chromophores in poled host-guest thin films

A new class of chromophores has been fabricated that features both electron-releasing and electron-withdrawing groups fused via an intervening ethynyl moiety to the carbon framework of a (porphinato)metal complex. These species possess a number of unusual optical properties that include molecular first-order hyperpolarizabilities (β) of exceptional magnitude. [5-(4′-dimethylaminophenylethynyl)- 15-(4″-nitrophenylethynyl)-10,20-diphenylporphinato]copper(II) and [5-(4′-dimethylaminophenylethynyl)-15-(4″-nitrophenylethynyl )-10,20-diphenylporphinato]zinc(II) represent two archetypal members of this new class of exceptional nonlinear chromophores. One of these compounds, [5-(4′-dimethylaminophenylethynyl)- 15-(4″-nitrophenylethynyl)-10,20-diphenylporphinato]zinc(II), possesses β values near 5000×10^-30 esu at incident irradiation wavelengths of both 830 and 1064 nm and an off resonant β₍₀₎ value of approximately 800×10^-30 esu. A β₍₀₎ value of this magnitude indicates that these prototype chromophores based on our new design criteria rank with the very best organic chromophores for second harmonic generation that have been fabricated to date. This fact coupled with the observation that these chromophores are stable to heating at 250 °C in thin polyimide films, suggests that modification and elaboration of these structural motifs will dramatically impact the development of electrooptic devices as well as materials for efficient frequency doubling of incident irradiation (second harmonic generation).