Competition between hydrogen and halogen bonding in halogenated 1‐methyluracil: Water systems

Abstract

The competition between hydrogen‐ and halogen‐bonding interactions in complexes of 5‐halogenated 1‐methyluracil (XmU; X = F, Cl, Br, I, or At) with one or two water molecules in the binding region between C5‐X and C4O4 is investigated with M06‐2X/6‐31+G(d). In the singly‐hydrated systems, the water molecule forms a hydrogen bond with C4O4 for all halogens, whereas structures with a halogen bond between the water oxygen and C5‐X exist only for X = Br, I, and At. Structures with two waters forming a bridge between C4O and C5‐X (through hydrogen‐ and halogen‐bonding interactions) exist for all halogens except F. The absence of a halogen‐bonded structure in singly‐hydrated ClmU is therefore attributed to the competing hydrogen‐bonding interaction with C4O4. The halogen‐bond angle in the doubly‐hydrated structures (150–160°) is far from the expected linearity of halogen bonds, indicating that significantly non‐linear halogen bonds may exist in complex environments with competing interactions. © 2016 Wiley Periodicals, Inc.

Hybrid organic–inorganic CH3NH3PbI3perovskite building blocks: Revealing ultra‐strong hydrogen bonding and mulliken inner complexes and their implications in materials design

“…As such, the A•••HD motif is said to be directional when the angle formed by the three atoms A, H, and D (∠A•••HD) lies in the range 160–180° . In addition, there are discussions in the literature that suggest intermolecular interactions with the angles of approach in the 140–160° range can be regarded as the consequence of directional bonding . For CH 3 NH 3 PbI 3 , the ∠I•••HN (or the ∠I•••HC) formed by the three atoms I, H, and N (or I, H, and C) defines the directionality of hydrogen bonding.…”

Halogen bonding in mono‐ and dihydrated halobenzene

“…For iodine and astatine the aug‐cc‐pVDZ‐PP basis with corresponding relativistic effective core potential was employed, whereas all other atoms employed the 6‐31+G(d) basis set. This level of theory was chosen to facilitate comparison with our previous work on XmU‐H 2 O and XmU‐(H 2 O) 2 . In addition, the M06‐2X functional was found to be one of the best functionals for dissociation energies and geometries of X‐bonded dimers .…”

“…Because the σ‐hole is located along the extension of the YX bond, halogen bonds are highly directional with halogen‐bond angles typically very close to 180°. However, it has been shown that significantly non‐linear halogen bonds (with halogen‐bond angles 150°–160°) can occur, particularly in complex environments with competing interactions . The strength of halogen bonds is usually found to increase as the halogen group is descended .…”

A QTAIM exploration of the competition between hydrogen and halogen bonding in halogenated 1-methyluracil: Water systems

“…bonding interactions in complexes of 5-halogenated 1-methyluracil with one or two water molecules in the binding region between C4-X and C5=O6 (with X = F, Cl, Br, I or At) 22 see Figure 1, note in the previous paper we used a different atom numbering scheme C5-X ≡ C4-X and C4=O4 ≡ C5=O6. In the singly-hydrated systems, the water molecule was found to form a hydrogen bond with C5=O6 for all halogens; however, structures with a halogen bond between the water oxygen and C4-X were only found for X = Br, I and At.…”

“…Relaxed scans were created by varying the C4-X---O16(water) angle in steps of 1°, while all other geometrical parameters were freely optimized, see respectively. Note that the atom numbering scheme in sub- figure (a-b) differs from that used in the previous Using QTAIM to complement a previous energy-based approach 22 , we investigated the hydrogen and halogen bonding in the region between the C4-X/C4--X BCP and the C5--O6 BCP and associated bond-paths in the 5- …”