Interactions of Boranes and Carboranes with Aromatic Systems: CCSD(T) Complete Basis Set Calculations and DFT-SAPT Analysis of Energy Components

Abstract

The noncovalent interactions of heteroboranes with aromatic systems have only recently been acknowledged as a source of stabilization in supramolecular complexes. The physical basis of these interactions has been studied in several model complexes using advanced computational methods. The highly accurate CCSD(T)/complete basis set (CBS) value of the interaction energy for the model diborane···benzene complex in a stacking geometry exhibiting a B(2)H···π hydrogen bond was calculated to be -4.0 kcal·mol(-1). The DFT-SAPT/CBS approach, which is shown to reproduce the CCSD(T)/CBS data reliably asserted that the major stabilizing component was dispersion, followed by electrostatics. Furthermore, the effect of the benzene heteroatom- and exosubstitutions was studied and found to be small. Next, when aromatic molecules were changed to cyclic aliphatic ones, van der Waals complexes stabilized by the dispersion term only were formed. As the last step, interactions of two larger icosahedral borane cages with benzene were explored. The complex of the monoanionic CB(11)H(12)(-) exhibited two minima: the first stacked above the plane of the benzene ring with a C-H···π hydrogen bond and the second planar, in which the carborane cage bound to benzene via five B-H···H-C dihydrogen bonds. The DFT-SAPT/CBS calculations revealed that both of these binding motifs were stabilized by dispersion followed by electrostatic terms, with the planar complex being 1.4 kcal·mol(-1) more stable than the stacked one. The dianionic B(12)H(12)(2-) interacted with benzene only in the planar geometry, similarly as smaller anions do. The large stabilization energy of 11.0 kcal·mol(-1) was composed of dominant attractive dispersion and slightly smaller electrostatic and induction terms. In summary, the borane/carborane···aromatic interaction is varied both in the complex geometries and in the stabilizing energy components. The detailed insight derived from high-level quantum chemical computations can help us understand such important processes as host-guest complexation or carborane···biomolecule interactions.

Nonclassical B‐Hb⋯π interaction in diborane⋯localized‐π sandwiches: A DFT‐D3 study

“…For example, in case of F‐substituted DB, favorable interaction (positive ΔE values) is predicted from B3LYP functional which encounters interactions other than dispersion interaction (Table ). Thus, dispersive interaction is found to be the key component in stabilizing the complexes which is in line with the majority of literatures on the nature of B‐H b ⋯π interaction …”

“…Depending on the nature of π‐systems, H b ⋯X bond distances (distance measured between H b and the geometric mean of the π bond) vary within the range 2.55‐3.03 Å (Table ). In case of half sandwiches, the H b ⋯X distances in B 2 H 6 ‐O 2 , B 2 H 6 ‐C 2 H 4 , and B 2 H 6 ‐C 2 H 2 complexes are 2.55, 2.88, and 2.86 Å respectively, although slightly shorter distances (~2.50 Å) for the interaction of DB with arenes are reported in literatures . Recently, H b ⋯X bond distances of 2.37‐2.58 Å are also reported for boranes adsorbed on the surface of undoped/doped graphene model systems .…”

“…Moreover, presence of such non‐conventional hydrogen bonding has also been reported in between boron cluster and phenyl ring in Ir‐dithiolene‐phosphine complex . In addition to experimental results, a good number of theoretical studies have been performed on B‐H b ⋯π interactions . Such interactions are relatively weak with stabilization energy <5.0 kcal mol −1 .…”

“…Recently, possible application of B‐H b ⋯π interaction as carrier for boron compounds has been predicted theoretically and such interactions have been explored in the formation of stable sandwich and multidecker complexes . It is to be mentioned that, all the studies have been devoted to the interaction of H b atom with delocalized π‐electrons . However, studies on B‐H b ⋯π interaction involving localized π‐electrons have received little attention.…”

Structure, stability and spectral signatures of monoprotic carborane acid–water clusters (CBWn, where n = 1–6)

“…In fact these types of interactions have been found in biological and chemical sciences. 45,46,50,51 The B-H À Á Á ÁH-O type of interaction is known as a dihydrogen bond (DHB) because the link between the two molecules within the complex is realized through the HÁ Á ÁH contact. It has been pointed out that one of the H atoms acting as the proton acceptor differs from typical acceptors such as oxygen and nitrogen atoms where the lone electron pairs are responsible for the existence of H-bonding.…”