Third order nonlinear optical properties of some organic nitroxyls

The degenerate four-wave mixing experiments have been performed in the dichloromethane solutions of 2,2,6,6-tetramethyl-pipridine-4-ol-N-oxyl p-hydroxybenzaldehyde oxime benzoic ester (TPOHBOBE) and bis-(TPOHBOBE) cobalt (II), respectively. The result is in agreement with the theoretical prediction of depending on the molecular chain length l as l⁵. A large off-resonant third order hyperpolarizability _xxxx of 1.3 × 10^–30 esu for bis-(TPOHBOBE) cobalt (II) was obtained. The corresponding value of the third order nonlinear optical susceptibility ⁽³⁾_xxxx for its solid state is estimated to be 7.8 × 10^–9 esu.