Intramolecular Hydrogen Bonding Appetency for Conformational Penchants in Oxalohydrazide Fluoro Derivatives: NMR, MD, QTAIM, and NCI Studies

Abstract

The conformational stability of synthesized diphenyloxalohydrazide and dibenzoyloxalohydrazide fluoro derivatives has been investigated by extensive NMR studies that are ascertained by various levels of theoretical calculations. Two-dimensional H-F HOESY NMR experiments revealed the close spatial proximity between two NMR-active nuclei, confirming the hydrogen bond (HB)-mediated interaction between them, further aiding in establishing the probable stable conformations of these molecules. The relaxed potential energy scan disclosed the energy-minimized most stable structure among the several possible multiple conformations, which is in concurrence with NMR interpretations. Atomistic molecular dynamics simulations have been employed to unequivocally establish the conformational stability and the nature of HB formation at varied temperatures. With the possibility of occurrence of a number of probable conformations, the percentage of occurrences of different types of HBs in them was determined by MD simulations. Their population analysis was carried out using a Boltzmann distribution, in addition to deriving their Gibbs free energies. The molecular interactions governing the stable conformations have not only been ascertained by experimental NMR interpretations but also corroborated by other theoretical computations, viz., quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI).

Molecular Dynamics Simulations of Self-Healing Topological Copolymers with a Comblike Structure

“…The combination of noncovalent interaction (NCI) analysis and molecular dynamics (MD) has been widely used to reveal molecular-level information, preferable interactions, and structural performance predictions for different systems. − Here, we employ the framework of the NCI analysis as a means to parametrize the interactions of the coarse-grained model. NCI is a powerful tool to reveal noncovalent interactions in real space based on the electron density (ED) and the reduced density gradient (RDG) .…”

The Strength of Hydrogen Bonds between Fluoro-Organics and Alcohols, a Theoretical Study

“…17−19 According to a recent review, "it is now difficult to doubt the existence of hydrogen bonds involving organic fluorine." 20 Despite the controversial existence of HBs with organic fluorine, fluoro-organics have been implicated as HB acceptors with a variety of donors, the most common being CH, NH, 21 and OH. 20 Within this list, the HB with CH is somewhat contentious.…”

Synthesis of Nonaromatic Macromolecular Luminogens, DFT Studies on Photophysics, and O‐Donor Selective On−Off Sensors: Contributions of In Situ N‐(Methylol)Acrylamido Comonomers

“…[80] In ML1, ML2, Cu(II)-ML1, Fe(III)-ML2, and aggregates of ML1/ML2, hydrogen bond formations were analyzed from RDG plots by using the NCI index based visualization technique. [80,81] The different types of hydrogen bonding were confirmed from scattered points at λ 2 < 0 in ML1 and ML2 (Figure 6a C 0 in ppm; b) q max and b q exp in mg g −1 ; c) k L in L mg −1 , and; d) k 2 in g mg -1 min -1 .…”