Abstract
Ab initio calculations were used to analyze interactions of with 1–4 molecules of NH3at the MP2/6-311++G(d,p) and the B3LYP/6-311++G(d,p) computational levels. In addition to H3B–H⋯H–NH2dihydrogen bond, the H2N–H⋯NH3hydrogen bonds were also predicted in clusters. Negative cooperativity in clusters constructed from mixed H3B–H⋯H–NH2dihydrogen and H2N–H⋯NH3hydrogen bonds are more remarkable. The negative cooperativity increases with size and number of hydrogen bonds in cluster. The B–H stretching frequencies show blue shifts with respect to cluster formation. Greater blue shift in stretching frequencies was predicted for B–H bonds which did not contribute to dihydrogen bonding with NH3molecules. The structures were analyzed with the atoms in molecules (AIM) methodology.
Highlights
Hydrogen is an ideal energy carrier; the binary boron-hydrogen compounds or boranes are the core of hydrogen storage and are an extremely rich area of boronbased cluster chemistry
The S22 could be considered as a cluster which is obtained from BH4− ion, and interaction of an H2N–H⋅ ⋅ ⋅ NH3 dimer with a it consists of two DHBs and an hydrogen bonded (HB) interaction
If we propose the S31 as a combination of S1 and S22, ΔECE(S31) = ΔE(S31) − (ΔE(S22) + ΔE(S1)) = −18.63 − ((−6.53) + (−12.78)) = 0.68, which shows that S31 is not cooperative with respect to S1 and S22
Summary
Hydrogen is an ideal energy carrier; the binary boron-hydrogen compounds or boranes are the core of hydrogen storage and are an extremely rich area of boronbased cluster chemistry. The borohydride complexes NaBH4 and LiBH4 possess a high capacity for hydrogen retention, and the release of hydrogen from NaBH4 is only possible via hydrolysis [1,2,3,4]. Quantum-chemical calculations performed on dimers, trimers, and more complicated self-associates of simple molecules, like H2O and HCN, revealed that the hydrogenbonding energies in the linear associates are remarkably higher than the values in dimers, which is due to mutual polarization of bonds. This cooperativity effect increases with the chain length of the associates. In contrast to those aforementioned, theoretical investigations of branched complexes in which two or more hydrogen bonds are formed by one proton-acceptor group predicted an inverse effect
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