[Study on the auxochrome of the electronic spectrum of organic compounds and its effect mechanism (I)].

This paper discusses the effect mechanism of auxochrome of electronic spectrum. The study proves that the auxochrome does not invariably make the maximum absorption wavelength of chromophore shift towards lower photon energy. For the transition of n-->pi*, the p orbit of the auxochrome interacts with the minimum antibonding empty orbit(pi*), which will make the energy of pi* increase, while the p orbit of the auxochrome is perpendicular to the n orbit of chromophore, and the energy of the n orbit will remain steady ultimately, so the transition energy of n-->pi* will increase. For the transition of pi-->pi*, the interaction of p orbit of the auxochrome and maximum bonding orbit (pi) of the chromophore forms new orbits, so the energy of the maximum bonding orbit in new orbits will increase. In some compounds, the increase is higher than those of pi*, so the transition energy of pi-->pi* will decrease and absorption wavelength will shift towards lower photon energy, which, however, is reverse in other compounds.