Third-order nonlinear optical properties of unsymmetric pentamethine cyanine dyes possessing benzoxazolyl and benzothiazolyl groups

A series of unsymmetric pentamethine cyanine dyes featuring benzoxazolyl and benzothiazolyl groups were synthesized, the structures were characterized by H-1 NMR, UV-vis absorption spectroscopy and mass spectrometry. The dyes with different anions such as chloride, tetraphenylborate and tetra(4-fluorophenyl)borate were also obtained and their solubility can be changed by the choice of the anion part. The third-order nonlinear optical properties were measured by the Z-scan technique with a pico-second laser beam at 532 nm in DMF solution. The third-order nonlinear optical susceptibilities chi((3)) and the second-order hyperpolarizabilities gamma' were obtained. The results reveal that these dyes exhibit strong reverse saturable absorption and nonlinear refraction. (C) 2012 Elsevier Ltd. All rights reserved.