1. Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of, the Ministry of EducationCollege of Chemistry and Materials ScienceNorthwest University Xi'an 710127 P. R. China
2. School of PhysicsNorthwest University Xi'an 710127 P. R. China
3. Center for Nanosystems Chemistry & Institut für Organische ChemieUniversität Würzburg Am Hubland 97074 Würzburg Germany