Complex of Lewis Acid and Substrate (IMAGE) Technical University of Munich (TUM) Caption The bulky Lewis acid (above) shields one side of the substrate (bottom) pushing the photoreaction in to the direction of the desired product. Furthermore the complex of Lewis acid and substrate requires a lower excitation energy than the substrate alone. Radiating the complex with light of this wavelength favors the formation of the desired substance while it delivers not enough energy for the non-specific photoreaction of the uncomplexed substrate. Credit Image: Richard Brimioulle Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.