Experimentally Established Benchmark Calculations of 31P NMR Quantities

The accuracy of different density function theory functionals and the MP2 approximation in P-31 NMR calculations has been evaluated for ten phosphorous containing molecules in which the phosphorous atoms are not involved in intermolecular interactions. The obtained absolute chemical shielding tensors are compared to experimental ones. The dependence of the numerical values on the size of basis sets has been inspected from the 6-311G(2d,p) to the pcSseg-3 basis sets. General recommendations on the most reliable functionals and the smallest possible size of a basis set have been reported. For example, the use of the M06L functional should be avoided. For five polycrystalline samples, the conformation of molecules has been identified with a high precision. These structures have been used to determine the reference values of the absolute chemical shielding for the TPSSh, B3LYP, and omega B97XD functionals and different basis sets. As reported in the supporting information, these structures can be used to determine the reference value of the absolute chemical shielding for any approximation of interest.