Assessment of various density functionals for intermolecular N → Sn interactions: The test case of poly(trimethyltin cyanide)

An assessment of the ability of various density functionals to reproduce the experimental structure of poly(trimethyltin cyanide) has been presented. Poly(trimethyltin cyanide) is one of the simplest linear organotin coordination polymers with intermolecular N → Sn interactions. In this work a set of 28 density functionals belonging to several density functional theory (DFT) classes and five different basis sets are considered. One-dimensional periodic boundary conditions (PBCs) are included in the calculations in order to reliably represent the infinite linear chain of the polymer. The results of the assessment prove to be dependent on the size of the basis set employed. The ωB97X hybrid functional combined with triple-ζ basis sets (such as def2-TZVP and cc-pVTZ) is able to reproduce the experimental structure of the polymer most accurately. The SOGGA11-X hybrid functional performs best when it is combined with double-ζ basis sets (such as def2-SVP and DGDZVP). Of non-hybrid DFT classes, selected functionals belonging to the generalized gradient approximation (e.g., BP86/def2-TZVP) also predict the structure of the polymer with sufficient accuracy (the errors in distances and angles are lower than 0.05 Å and 1.0°, respectively). We find that the performance of SOGGA11 is very poor, irrespective of the basis set used. The reproduction of the experimental structure of the polymer can be improved greatly by including a fraction of Hartree–Fock (HF) exchange in SOGGA11, as it is exemplified by SOGGA11-X.