Theoretical Insights into Regulation of Red/Blue-Shifting Hydrogen Bonds Through Cooperativity with Regium Bonds

Le résumé fourni par la source

To deeply understand the characteristics and regulation of red/blue-shifting hydrogen bonds (HBs), a theoretical investigation was conducted to explore the cooperativity between regium bonds and HBs in the complexes of Y···MCN···HCX 3 (M = Cu, Ag, Au; Y = H 2 O, HCN, NH 3; X = F, Cl). When MCN formed a hydrogen bonding dimer with CHF 3 or CHCl 3, the blue shift of C–H vibration frequency v (C–H) decreases as the following sequence Au > Cu > Ag, and the red shift decreases following the order Ag > Cu > Au. Upon the formation of ternary complexes, the presence of regium bonding interactions exerts a positive synergistic effect, resulting in the strengthening of the HBs. This, in turn, leads to noticeable changes in the red and blue shifts of v (C–H). In CHF 3 complexes, v (C–H) undergoes a decrease in the blue shift, whereas that in CHCl 3 exhibits an increase in the red shift. Especially, a transition from blue to red shift is observed within the AuCN···HCCl 3 complex. As the strength of the regium bond increases, the trend of shifting from blue to red becomes more pronounced. For a given MCN, the changes occur in the order of NH 3 > HCN > H 2 O. The interplay between two interactions was revealed by the molecular electrostatic potentials (MEP), the atoms in the molecule (AIM), and natural bond orbitals (NBO) analysis. It is revealed that Δ v (C–H) is linearly correlated with a series of configuration and energy parameters. We explain the red- and blue-shifting HBs and their changes from the perspective of hyperconjugation and rehybridization. The presence of the positive synergistic effect enhances the hyperconjugation effect, thereby leading to a reduction in the blue shift and an increase in the red shift of v (C–H) within the complexes. This study enriches previous mechanisms regarding red- and blue-shifting HBs and introduces a novel idea to manipulate the characteristics of HBs, with the potential to impact the functioning of intricate systems.

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