Synthesis, characterization and evaluation of the photophysical and nonlinear optical behaviour of novel 4-substituted arylidene-2-[5-(2,6-dichlorophenyl)-3-methyl-1,2-oxazol-4-yl]-1,3-oxazol-5-ones

• Amongst the oxazolyloxazolones the dialkylamino substituted derivatives exhibited the highest λmax and λem in DMF.
• The nonlinear refractive index is found to be negative and its magnitude is of the order of 10−11 esu.
• The molecular two photon absorption cross-sections are of the order of 10−46 cm4 s/photon.
• Values of two photon absorption cross-section are nearly two orders of magnitude larger than of Rhodamine 6G.
• Molecules with –NR2 substituents exhibited better optical limiting behaviour.

Five new 4-substituted arylidene-2-[5-(2,6-dichlorophenyl)-3-methyl-1,2-oxazol-4-yl]-1,3-oxazol-5-ones have been designed and synthesized in order to study their third-order nonlinear optical properties. These novel compounds were characterized by advanced spectroscopic techniques (IR, 1H, 13C NMR, ESI-MS spectroscopy and elemental analyses). In addition, the evaluation of absorption and emission wavelengths of the new 5-oxazolone derivatives was carried out in seven different solvents of varying polarity, which showed intense absorption maxima at 350–480 nm and emission maxima at 390–535 nm respectively. The third-order nonlinear optical properties of the target molecules have been investigated in N,N-dimethylformamide using a single beam Z-scan technique with nanosecond laser pulses at 532 nm. The nonlinear refractive index, nonlinear absorption coefficient, magnitude of third-order susceptibility and molecular two photon absorption cross-sections have been determined. All of the compounds showed excellent optical limiting behaviour at 532 nm, with the best optical limiting behaviour observed with strong electron donor [dimethyl and N,N-diethyl amino] substituents.

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