A Quantum-Chemical and Correlation Study of the Ionization of Purpurin

摘要

Anthraquinoid tautomers participate in the ionization of purpurin.The tautomerism takes place in both ground and excited states of the molecules;the excited state is more sensitive to the tautomerism.The solvation and ionization shift the tautomeric equilibria.In the experimental absorption spectra of purpurin,the major bands correspond to the 9,10-,1,4-,and 1,10-anthraquinoid tautomers;anions with the 9,10-anthra-quinoid structure are not detected.The position and intensity of the pi,pi* bands,and also the quantum-chemical parameters linearly correlate with the degree of ionization of purpurin.