Crystallographic and ab initio study of pyridine CH–O interactions: linearity of the interactions and influence of pyridine classical hydrogen bonds

Abstract

The CH-O interactions of pyridine with water molecules were studied by analysing the data in the Cambridge Structural Database (CSD) and by ab initio calculations. The analysis of the CH-O interactions in the crystal structures from the CSD indicates that pyridine C-H donors do not show preference for linear contacts. The results of the ab initio calculations are in accord with the CSD data and show that stabilization energy is larger for bifurcated interactions than for linear interactions. The calculated interaction energies at the MP2/cc-pVQZ level for linear CH-O interactions between water and pyridine ortho, meta, and para C-H groups are −1.24, −1.94 and −1.97 kcal mol −1 , respectively. The calculated energies for bifurcated ortho-meta and meta-para interactions are −1.96 and −2.16 kcal mol −1 . The data in the crystal structures from the CSD and ab initio calculations show a strong influence of simultaneous classical hydrogen bonds of pyridine on the CH-O interactions. The results show that simultaneous hydrogen bonds strengthen the CH-O interaction by about 20%. The calculated interaction energies for linear CH-O interactions between water and pyridine, with simultaneous hydrogen bonds, for ortho, meta, and para C-H groups are −1.64, −2.34, and −2.33 kcal mol −1 , respectively, while those for ortho-meta and meta-para bifurcated interactions are −2.44 and −2.58 kcal mol −1. The energies of the meta-para bifurcated interactions calculated at the CCSD(T)(limit) level for pyridine without and with hydrogen bonds are −2.30 and −2.69 kcal mol −1, respectively. The result that nonlinear interactions are energetically favoured can be very important for recognizing the CH-O interaction of heteroaromatic rings in the crystal structures and biomolecules.

Cooperativity in alkane‐1,2‐ and 1,3‐polyols: NMR, QTAIM, and IQA study of O─H…OH and C─H…OH bonding interactions

“…Whereas the BCPs for O─H … OH interactions in 1,2‐polyols are unstable, there is a surprisingly large number of stable C─H … OH interactions, starting with one in tetrol 10 and rising to seven in heptol 13 , with the same numbers in the corresponding pyridine complexes. Consistent with previous work 104–106 on C─H … OH bonding between aromatic C─H protons and various acceptor oxygens in the solid state, there is no preference for linearity: For the 16 such interactions in polyols 10 – 13 , the bond angles range from 103° to 126° with an average of 114 ± 9°. The ρ values for the critical points differ by about 0.001 a.u.…”

Weak Interactions and Conformational Changes in Core-Protonated A2- and Ax-Type Porphyrin Dications

“…Non-standard hydrogen-mediated bonding interactions are approximately linear, with distances indicating associative interactions, the shortest of which is 3.064 Å, well below the sum of the Van der Waals radii for C and O. These types of C–H⋯O are common from cationic moieties [ 44 ].…”

Nature of the water/aromatic parallel alignment interactions

“…In addition to strong hydrogen bonds, water molecules also have important weaker interactions that enable interactions of nonpolar groups with polar solvent. It is known that the interaction of water molecules with aromatic ring systems can be of the type HOH···π or H 2 O···HC . In the first case, one of the OH bonds of water is perpendicular to the ring plane and situated above the ring.…”