Contribution of edge-carbon atoms and non-benzenoid rings in graphitic carbons to π* peak profiles in CK-XANES
Yasuji Muramatsu and Yuma Hirai
University of Hyogo
Abstract
To analyze the local structure of non-benzenoid rings in graphitic carbons by soft X-ray absorption spectroscopy, CK-XANES of aromatic compounds having pentagonal or heptagonal rings were theoretically analyzed by the first principle calculations. Edge-carbon atoms split the π* peak into two peaks in CK-XANES. Pentagonal rings in polycyclic aromatic hydrocarbon structure disturb delocalization of π electrons in hexagonal rings. Hence, pentagonal rings split the π* peak into two peaks in CK-XANES. It is also confirmed that heptagonal rings play a role of a hole in hexagonal carbon layer, and the heptagonal carbon atoms can be regarded as edge carbon atoms. Hence heptagonal rings also split the π* peak into two peaks. Consequently, edge-carbon atoms and non-benzenoid rings make the π* peak wider than hexagonal rings.
Keywords: Soft X-ray, XANES
Topic: Polymer