Solid State Structure Prediction Through DFT Calculations and ¹³C NMR Measurements: Case Study of Spiro-2,4-dithiohydantoins

Abstract

We present a DFT approach for precise estimation of the intermolecular effects on the experimental and calculated ¹³C NMR shifts for a series of 5-spiro-2,4-dithiohydantoins (1–5), both in solid state and in solution. It has been found that the used B3LYP/6-31+ G^** method gives very good agreement with the experimental structural and the NMR parameters, provided the intermolecular hydrogen bonds are properly considered. For correct description of the experimental NMR shifts in solid state we have initially used the isolated-molecule and the cluster approaches for GIAO calculations of the NMR shifts, followed by periodic boundary condition calculations of the structure and the nuclear magnetic shielding constants by the GIPAW method implemented in the Quantum Espresso code. The best agreement with the experimental solid state data is obtained for the optimized small cluster (a trimer of molecules) in the calculations using the atom-centered orbitals. Excellent agreement between the ¹³C CPMAS NMR and the GIPAW calculated shift is obtained for fully relaxed bulk structures of compounds 1–5. This has been used as a final verification of the proposed solid state structure of compound 5 whose crystal structure is unknown yet.