1. The main group chemistry involves all elements of the s- and p-blocks (groups 1 and 2 and 13–18 of the Periodic Table respectively) with conventional exceptions of H C and N.
2. The chalcogens (group 16) include O S Se Te and Po. The chemical properties of O are rather different from those of other members of the group and normally it is not included into discussion of chalcogen chemistry whereas chemistry of radioactive Po did not receive attention comparable with that of S Se and Te.
3. T. Chivers A Guide to Chalcogen-Nitrogen Chemistry World Scientific 2005.
4. Comprehensive Heterocyclic Chemistry III. Eds. A. R. Katritzky C. A. Ramsden E. F. V. Scriven R. J. K. Taylor Elsevier:2008.
5. The CT complex is a DA complex characterized by electronic transitions to an excited state in which there is a partial transfer of electronic charge from donor to acceptor:IUPAC Compendium of Chemical Terminology (The Gold Book) Eds. A. D. McNaught A. R. Wilkinson Blackwell Scientific Publications 1997.