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The implantation of metal ions into photorefractive materials followed by thermal annealing leads to an increase in resonance optical absorption as well as an enhancement of the nonlinear optical properties. We have implanted ions of Au (3.6 MeV), Ag (1.5 MeV) and Cu (2.0 MeV) into pure silica followed by careful heat treatment. Using optical absorption spectrophotometry and rutherford backscattering spectrometry we have measured the cluster size for each heat treatment temperature and determined the activation energies for their formation. The third order electric susceptibility for silica with 2 nm gold clusters has been determined by Z-scan to be 65×10−8 esu.

Inspired by the diversity created by nature, organic chemists have been using a divergent strategy to improve the synthetic efficiency of diverse molecules. Transition-metal-catalyzed C–H functionalization has become one of the most straightforward, powerful, and atom-economical methods to construct complex scaffolds. However, C–H activation initiated divergent transformation to prepare diverse molecules is still limited. To address this challenge, we herein developed Rh­(III)-catalyzed C–H olefination/annulation reaction cascades to divergently construct diverse polyheterocycles by tuning manipulations of directing groups (DGs). Up to 9 distinct scaffolds were creatively synthesized under simple conditions with good functional group tolerance, chemo-, and regioselectivity. Such a versatile strategy and its extension may encourage researchers to discover more promising manipulations of DGs for transition-metal-catalyzed C–H bond activation, making diverse available targets and materials that would have been previously out of range.

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The schematic of the experimental system.