Modulation of Stacking Interactions by Transition‐Metal Coordination: Ab Initio Benchmark Studies

Abstract

A series of ab initio calculations are used to determine the C--Hpi and pipi-stacking interactions of aromatic rings coordinated to transition-metal centres. Two model complexes have been employed, namely, ferrocene and chromium benzene tricarbonyl. Benchmark data obtained from extrapolation of MP2 energies to the basis set limit, coupled with CCSD(T) correction, indicate that coordinated aromatic rings are slightly weaker hydrogen-bond acceptors but are significantly stronger hydrogen-bond donors than uncomplexed rings. It is found that pipi stacking to a second benzene is stronger than in the free benzene dimer, especially in the chromium case. This is assigned, by use of energy partitioning in the local correlation method, to dispersion interactions between metal d and benzene pi orbitals. The benchmark data is also used to test the performance of more efficient theoretical methods, indicating that spin-component scaling of MP2 energies performs well in all cases, whereas various density functionals describe some complexes well, but others with errors of more than 1 kcal mol(-1).

Coordination-Induced Molecular Tweezing: Ruthenium Clusters Docked at Azuliporphyrinogens

“…56 Theoretical studies have also confirmed that coordinated aromatics interact through stronger stacking. 57,58 It is worth mentioning that, in the solid state, the carbonylruthenium(II) azuliporphyrin tetraruthenium cluster complex exhibits a similar structural motif of azulene−azulene interaction. The azulene rings of two inversion-related molecules interact in a stacking manner reflected by a C•••C closest distance of 3.462(17) Å.…”

“…The ring deformation might lead to a decreased delocalization of π-electrons, but even fragments with double-bond localization can still produce attractive interactions . Theoretical studies have also confirmed that coordinated aromatics interact through stronger stacking. , …”

Aromatic Rings in Chemical and Biological Recognition: Energetics and Structures

“…Theoretical studies on π–π interactions have been summarized in a review,12 and new calculations have appeared on their cooperative interplay with other intermolecular interactions,13 substituent effects,14 and the effects of transition‐metal coordination 15. Additionally, numerous calculations on aromatic–aromatic interactions of different homo‐ and heterodimers have been reported,16 such as for benzene,17 toluene,18 nitrobenzene,19 pyridine,20 azulene,21 triphenylene,22 coronene,23 DNA bases,24 porphine,25 aromatic amino acids,26 and others 27…”

Applications and validations of the Minnesota density functionals

“…Mutter and Platts [167] employed a series of ab initio methods to determine the C-HÁÁÁp and pÁÁÁp stacking interactions of aromatic rings coordinated to transition-metal centers. They also used the benchmark data to assess the performance of some lower-cost methods including DFT.…”