Investigation of Heavy Atom Effect of Organobismuth Compounds based on NMR Chemical Shifts Estimated by Experimental Measurements and Theoretical Studies

In this paper, the heavy atom effect of organobismuth compounds synthesized by the author was discussed based on experimental and theoretical studies. NMR chemical shifts of organobismuth compounds are often influenced by the heavy atom effect derived from bismuth atom. In the case of bismabenzene and bismacyclobutadiene synthesized by the author and co-workers, the NMR signals assigned to be hydrogen and carbon nuclei were observed at unusual low-field region, probably due to the unique heavy atom effect. To get insight into the heavy atom effect of such compounds, I performed theoretical calculations by using Gaussian program package. Based on the comparison of chemical shifts estimated by experimental and theoretical methods, the heavy atom effect of organobismuth compounds was discussed in detail.