Abstract

Noncovalent interactions are among the main tools of molecular engineering. Rational molecular design requires knowledge about a result of interplay between given structural moieties within a given phase state. We herein report a study of intra- and intermolecular interactions of 3-nitrophthalic and 4-nitrophthalic acids in the gas, liquid, and solid phases. A combination of the Infrared, Raman, Nuclear Magnetic Resonance, and Incoherent Inelastic Neutron Scattering spectroscopies and the Car–Parrinello Molecular Dynamics and Density Functional Theory calculations was used. This integrated approach made it possible to assess the balance of repulsive and attractive intramolecular interactions between adjacent carboxyl groups as well as to study the dependence of this balance on steric confinement and the effect of this balance on intermolecular interactions of the carboxyl groups.

Highlights

  • Hydrogen bonding (H-bonding) and steric effects are important tools of molecular engineering.Under certain conditions, their interplay can stabilize species that otherwise exhibit high chemical reactivity [1,2,3,4]

  • The main main aim aim of of this this study study was was to tocharacterize characterize intramolecular intramolecular interactions interactions between between adjacent adjacent carboxyl groups in the presence and absence of intramolecular steric effects and the carboxyl groups in the presence and absence of intramolecular steric effects and the effect effect of of all all these these interactions on intermolecular interactions of these carboxyl groups

  • For a comprehensive spectroscopic investigation of 3 and 4, we accomplished a study based on IR, Raman, and Inelastic Neutron Scattering (IINS) measurements, as well as density-functional theorytheory (DFT), Car–Parrinello molecular dynamics (CPMD), and Potential Energy Distribution (PED) calculations

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Summary

Introduction

Hydrogen bonding (H-bonding) and steric effects are important tools of molecular engineering. In the simplest case of salicylic acid crystals, the carboxyl groups of the molecules form dimers while their hydroxyl groups form intramolecular groups of [31,32]. In when the number of competing interactions increases, the co-crystals of salicylic acid of contrast, salicylic acid exhibit polymorphism and different solubility [32,34,35]. These changes are critically important for important for pharmaceutical applications. H-bond in salicylic acid derivatives can derivatives can be controlled through intramolecular steric effects. The domination of cis conformation of carboxyl group, effect of H-bonds on the conformational state of compounds.

Chemical
Results and Discussion
Dynamics of Hydrogen Bonding within the Framework of Molecular Dynamics
Method
H chemical
H NMR spectra of Figure 88 shows shows characteristic characteristic 11H
H NMR spectra of 4 in CDCl in the presence
Characteristic
H-Bonding Vibrational Modes in Carboxyl Dimers
11. Normalized
Compounds and Deuteration
Infrared and Raman Measurements
NMR Measurements
Car–Parrinello Molecular Dynamics’ Simulations
DFT Calculations
Conclusions

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