Interplay of Hydrogen, Pnicogen, and Chalcogen Bonding in X(H₂O)_n=1–5 (X = NO, NO⁺, and NO^–) Complexes: Energetics Insights via a Molecular Tailoring Approach

Hydrogen bond strengths in microhydrated clusters of HNO and HONO: energetic insights via a molecular tailoring approach

“…It may be noted that, unlike HNO, cis and trans isomers are possible for HONO, where trans -HONO is more stable 13,26 than cis -HONO by 0.51 kcal mol −1 at the MP2/aug-cc-pVTZ//MP2/6-311++G(d,p) level. In our previous study, 48 we noted that the most positive MESP values ( V max ) lie above the N atom of the N–O bond axis of the NO molecule and are responsible for pnicogen bonding with the H 2 O molecule. Interestingly, no such V max values are found around the N–O bond of HNO and cis -HONO, but the trans -HONO has a slight electron-deficient region ( V max = 11.7 kcal mol −1 ) on the N-atom.…”

“…In our previous study on microhydration of NO, NO + , and NO − species, it has been observed that self-association of water clusters is energetically preferred for neutral NO(H 2 O) n complexes, while cross-association is seen in the most stable complexes of NO − (H 2 O) n and NO + (H 2 O) n congeners. 48 This is due to the weak NO⋯water interactions in NO(H 2 O) n complexes as opposed to the strong NO − ⋯water and NO + ⋯water interactions in their respective microhydrated complexes.…”

“…Upon comparing these HBs with the HBs of NO and NO − in their microhydrated complexes, the HBs formed by NO with water are very weak (energies ranging from −0.10 to 2.10 kcal mol −1 ), while the HBs formed by NO − are the strongest (from 9.26 to 17.29 kcal mol −1 ). 48 The strong HBs formed between NO − and water are attributed to the additional charge on NO when compared to the HBs formed by other neutral molecules with water (NO, HNO, and HONO). 61…”

“…In our recent work, we quantified the energetics and cooperativity contribution of individual noncovalent interactions present in the microhydrated networks of NO, NO + , and NO − species. 48 It has been shown that different types of noncovalent interactions such as hydrogen, pnicogen, and chalcogen bonding and their interplay can be conveniently addressed by using the MTA based method. This allows us to investigate various water-assisted reactions of neutral and redox species of NO based on the energetics of individual noncovalent interactions.…”

Molecular Tailoring Approach for the Direct Estimation of Individual Noncovalent Interaction Energies in Molecular Systems

“…On the other hand, in the NO + (H 2 O) n complexes, strong PBs (up to 30.0 kcal/mol) are found along with moderate CBs (up to 18.0 kcal/mol), and the relatively weakest water···water HBs (up to 10.0 kcal/mol). The HB interaction of NO via both N and O atoms with water molecules was found to be strong (up to 17.0 kcal/mol) in NO – (H 2 O) n complexes . It should be noted that the MTA-based method works well for the microhydrated ionic congeners of NO, since the positive or negative charge seems to be localized on the NO moiety.…”