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Second harmonic generation studies of metal and non-metal porphyrins at silica surfaces

Abstract:

Resonant molecular optical second harmonic generation (SHG) was obtained from [2, 3, 7, 8, 12, 13, 17, 18-Octaethyl-porphinato]M, with M = none, vanadyl and Ni(II), adsorbed onto fused silica substrates. The polarization dependence of the SHG signals at 1064nm allowed the determination of average molecular orientations. For the vanadium porphyrin the average angle between the long axis molecules and the surface normal was 38°, while, for the Nickel porphyrin, and the non-metal porphyrin the angle was close to 0°. These results can be understood in terms of the different symmetries of the molecules.