The effect of hydrogen-bonding cooperativity on the strength and properties of σ-hole interactions: an <i>ab initio</i> study

2017-03-09T17:29:50Z (GMT) by Mehdi D. Esrafili Mahshad Vakili
<p><i>Ab initio</i> calculations at the MP2/aug-cc-pVTZ level of theory are performed to investigate the effect of hydrogen-bonding cooperativity on the strength and bonding properties of σ-hole interaction in linear FCl⋅⋅⋅(NCH)<i><sub>n</sub></i><sub>=2</sub><sub>–</sub><sub>5</sub>, FHS⋅⋅⋅(NCH)<i><sub>n</sub></i><sub>=2</sub><sub>–</sub><sub>5</sub>, FH<sub>2</sub>P⋅⋅⋅(NCH)<i><sub>n</sub></i><sub>=2</sub><sub>–</sub><sub>5</sub> and FH<sub>3</sub>Si⋅⋅⋅(NCH)<i><sub>n</sub></i><sub>=2</sub><sub>–</sub><sub>5</sub> clusters. It is found that the cooperative effects in the hydrogen-bonding tend to strengthen the σ-hole interaction. However, these effects are almost saturated in the larger clusters (<i>n</i> > 5). For a given cluster, the amount of bond contraction in FCl⋅⋅⋅(NCH)<i><sub>n</sub></i> is more important than other systems. A nice linear relationship is found between the σ-hole bond energies and absolute <sup>15</sup>N chemical shieldings or spin–spin coupling constants across the σ-hole bond.</p>