Nonlinear optical absorption properties of two multisubstituted p-dimethylaminophenylethenyl pyridiniums

Two multisubstituted D-π-A type pyridinium salts, N-methyl-2,6-di[(E)-p- dimethylaminophenylethenyl]-pyridinium iodide (1) and N-methyl-2,4,6-tri[(E)-p- dimethylaminophenylethenyl]pyridinium iodide (2), were synthesized with good yields by a modified method, and the structure of 1 was confirmed by X-ray diffraction. The nonlinear optical absorption (NOA) properties of the two compounds in the solution state were investigated by the Z-scan technique. Compounds 1 and 2 both exhibited very strong saturated absorption at picosecond pulse, and 1 displayed reverse saturated absorption, while 2 revealed saturated absorption properties at the nanosecond pulse. The electron-donating ability, number of side chains, and molecular coplanar characteristics of the compounds have a significant impact on their NOA properties.