Theoretical Investigation of the Weakly Dihydrogen Bonded Complexes FArCCH···HBeX (X = H, F, Cl, Br)

Rovibrational energy and spectroscopic constant calculations of complexes pairing via dihydrogen bonds

In the present investigation, we performed a thorough study of potential energy curves, rovibrational spectra, and spectroscopic constants for complexes pairing via dihydrogen bonds. In particular, we dealt with LiH···HX (X = F, CN, CCH, CCF, CCCl) complexes by employing accurate electronic energy calculations at the MP2/aug-cc-pVDZ level of theory. Following this, the Numerov method was applied to solve the nuclear Schrödinger equation, thus obtaining spectroscopic constants and rovibrational spectra. Good linear correlation between the magnitudes of the interaction energies for interaction of HX with LiH, and the most positive electrostatic potentials of hydrogen in HX, was established.

Wave Function and Density Functional Theory Studies of Dihydrogen Complexes

We performed a benchmark study on a series of dihydrogen bond complexes and constructed a set of reference bond distances and interaction energies. The test set was employed to assess the performance of several wave function correlated and density functional theory methods. We found that second-order correlation methods describe relatively well the dihydrogen complexes. However, for high accuracy inclusion of triple contributions is important. On the other hand, none of the considered density functional methods can simultaneously yield accurate bond lengths and interaction energies. However, we found that improved results can be obtained by the inclusion of nonlocal exchange contributions.

Cooperative and diminutive interplay between lithium and dihydrogen bonding in F3YLi…NCH…HMH and F3YLi…HMH…HCN triads (Y=C, Si; M=Be, Mg)

The F(3)YLi…NCH…HMH and F(3)YLi…HMH…HCN triads (Y=C, Si; M=Be, and Mg) are connected by lithium and dihydrogen bonds. To understand the properties of the systems better, the corresponding dyads are also studied. Molecular geometries, binding energies, infrared spectra and NMR properties of monomers, dyads, and triads are investigated at the MP2/6-311++G** computational level. Particular attention is paid to parameters, such as cooperative energies, and many-body interaction energies. Triads with the HMH molecule located at the end of the chain, show energetic cooperativity ranging between -3.66 to -7.59 kJ mol(-1). When the HMH molecule is located in the middle, the obtained cluster is diminutive with an energetic effect between 3.49 to 5.17 kJ mol(-1). The electronic properties of the complexes are analyzed using parameters derived from the atoms in molecules (AIM) methodology.

Cooperative and diminutive unusual weak bonding in F3CX···HMgH···Y and F3CX···Y···HMgH trimers (X = Cl, Br; Y = HCN, and HNC)

MP2 calculations with cc-pVTZ basis set were used to analyze intermolecular interactions in F(3)CX···HMgH···Y and F(3)CX···Y···HMgH triads (X = Cl, Br; Y = HCN, and HNC) which are connecting with three kinds of unusual weak interactions, namely halogen-hydride, dihydrogen, and σ-hole. To understand the properties of the systems better, the corresponding dyads are also studied. Molecular geometries, binding energies, and infrared spectra of monomers, dyads, and triads were investigated at the MP2/cc-pVTZ computational level. Particular attention is given to parameters such as cooperative energies, cooperative dipole moments, and many-body interaction energies. Those complexes with simultaneous presence of a σ-hole bond and a dihydrogen bond show cooperativity energy ranging between -1.02 and -2.31 kJ mol(-1), whereas those with a halogen-hydride bond and a dihydrogen bond are diminutive, with this energetic effect between 0.1 and 0.63 kJ mol(-1). The electronic properties of the complexes have been analyzed using the molecular electrostatic potential (MEP), the electron density shift maps, and the parameters derived from the atoms in molecules (AIM) methodology.

Theoretical Study of Dihydrogen Bonds between (XH)2, X = Li, Na, BeH, and MgH, and Weak Hydrogen Bond Donors (HCN, HNC, and HCCH)

The dihydrogen-bonded (DHB) complexes formed by (XH)2, with X = Li, Na, BeH, and MgH, with one, two, and four protonic molecules (HCN, HNC, and HCCH) have been studied. These complexes have been compared to those of the XH monomers with the same hydrogen bond donor molecules. The energetic results have been rationalized based on the electrostatic potential of the isolated hydridic systems. The electron density properties have been analyzed within the AIM methodology, both at the bond critical points and the integrated values at the atomic basins. Exponential relationships between several properties calculated at the bond critical points (rho,nabla2rho, lambdai, G, and V) and variation of integrated properties (energy, charge, and volume) vs the DHB distance have been obtained.

Theoretical Investigation of the Dihydrogen Bond Linking MH2 with HCCRgF (M = Zn, Cd; Rg = Ar, Kr)

An ab initio computational study of the properties of four linear dihydrogen-bonded complexes pairing MH2 (M = Zn, Cd) with HCCRgF (Rg = Ar, Kr) was undertaken at the MP2/DGDZVP level of theory. The calculated complexation energies of the linear complexes vary between 6.5 kJ/mol for M = Zn to 8.5 kJ/mol for M = Cd. Equilibrium interatomic H...H distances are roughly 2.07 A for all four complexes. The red shifts of the H-C stretching frequency of HCCRgF correlate nicely with the interaction energies.