ENDOHEDRAL MAGNETIC SHIELDING IN FULLERENES - A GIAO CPHF STUDY

Ab initio GIAO CPHF calculations on the NMR chemical shifts of the noble gas guests in the He@C60, Ne@C60, He@C606-, He@C70, and He@C76 endohedral complexes are reported. Changes in shifts experienced by the guests upon encagement are found to be sensitive to the host geometries but only weakly dependent on the noble ps atom. For the He@C60 complex, good agreement between the shift calculated at the GIAO CPHF/6-31G&DZP level of theory and its experimental counterpart is obtained, and the differences among previous theoretical predictions are resolved. A simple theory explaining the observed trends in chemical shifts is outlined.