Quantum Chemical Calculations of NMR Chemical Shifts of Organic Molecules: XI.* Conformational and Relativistic Effects on the ~(31)P and ~(77)Se Chemical Shifts of Phosphine Selenides

摘要

Conformational and relativistic effects on the ~(31)P and ~(77)Se chemical shifts of phosphine selenides were analyzed in terms of the ZORA-GIAO-B1PW91/TZP approach. The effect of conformation of phosphine selenides related to internal rotation about the single P-C bonds was found to be insignificant, while the contribution of relativistic spin-orbit interaction to the calculated values of ~(77)Se chemical shifts did not exceed 10 ppm. On the other hand, relativistic effects arising from magnetic shielding of the phosphorus nucleus in the P=Se fragment by selenium are fairly strong (25-30 ppm), which indicates the necessity of including the contribution of relativistic spin-orbit interaction in the calculation of ~(31)P chemical shifts in phosphine selenides.