Two-photon absorption properties of dehydrobenzo[12]annulenes and hexa kis(phenylethynyl) benzenes: Effect of edge-linkage

Two-photon absorption (TPA) properties of two trefoil-shaped compounds with different edge linkages-tris(hexadehydrotribenzo[12]annulene) and tris(tetradehydrotribenzo[12]annulene)and three asterisk-shaped compounds having no edge-linkage-hexakis(phenylethynyl)benzenes-ore investigated experimentally by the open-aperture Z-scan and TPA-induced fluorescence methads with wavelength tuneable femtosecond pulses. The coma pound with ethynylene edge-linkage exhibits the most intense TPA (the maximal TPA cross section is 1300 +/- 170 GM at 572 nm where 1 GM= 10(-50) cm(4)s molecule(-1) photon(-1)). The TPA activity of the compounds is primarily explained in terms of the planarity of the molecules in relation with the type of edge-linkage.