To develop high SHG active materials with short cut-off wavelengths, “umbrella-shaped”tribenzamide derivatives were investigated. Crystals of these umbrella type materials are expected to show molecular columns due to van der Waals interactions. Tribenzamide ( 1)gave a powder SHG efficiency 1.5 times that of urea, and itsλis 330 nm in methanol. In the β calculation of 1 by the ab initio STO-3 G CPHF method, the β component of the direction along umbrella shaft was the largest. However in the crystal state, the component disappeared due to antiparallel alignment of packing columns. In other para-substituted tribenzamide derivatives with methyl and methoxy substituents, only two compounds showed SHG efficiency.
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