Unraveling the polymorphism of [(p -cymene)Ru(κN-INA)Cl₂] through dispersion-corrected DFT and NMR GIPAW calculations

The structural and ¹³C/¹H NMR parameters of the four crystal forms (1α, 1·H₂O, 1β, and 1γ) of the solid wheel-and-axle (WAA) metal-organic compound [(p-cymene)Ru(κN-INA) Cl₂] have been studied by means of periodic DFT calculations. The quality of the results obtained strongly depends on a correct description of long-range interactions; thus, in the geometry refinement protocol used, the pure DFT functionals need to be coupled with a dispersion-correction term (B3LYP-D2, B3LYP-D*). The solid-state ¹³C/¹H NMR δ_iso parameters and ¹³C MAS NMR spectra, calculated by means of the PBE-GIPAW method, agree well with the experimental data for the four crystal forms (mean absolute deviations of the ¹³C and ¹H δ_iso data values lie in the ranges 1.3-2.9 and 0.3-1.0 ppm, respectively). In this context, some revisions in the experimental assignment of the ¹³C/¹H NMR δ_iso parameters of the 1·H₂O, 1β, and 1γ crystal forms can be suggested. The mismatch in the assignment seems to be due to the rotation of the -COOH moiety, which occurs at the 1α-1·H₂O transition and was not considered in the experiments. Finally, the results obtained suggest the presence of two COOH···Cl hydrogen bonds of comparable strength established by the two molecules in the asymmetric unit of the 1γ polymorph, in partial disagreement with previous findings.