Research Paper on Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines: Thermodynamics and Spectroscopy

Description

Title: Halogen- and Hydrogen-Bonded Complexes of Haloforms with Aromatic and Aliphatic Amines: Thermodynamics and Spectroscopy

Abstract: The associations of CHX3 (X=I, Br, Cl) with aromatic (tetramethyl-p-phenylenediamine) and aliphatic (4-diazabicyclo[2,2,2]octane) amines were examined using UV-Vis and 1H NMR measurements, X-ray crystallography, and computational analysis to determine the similarities and differences between halogen and hydrogen bonding. The strengths of these complexes correlated with the electrostatic potentials on the surfaces of the interacting atoms when the polarization of haloforms was taken into account. Their spectral characteristics, however, were very different. While the UV-Vis spectra of the halogen-bonded complexes revealed new, strong absorption bands, those of their hydrogen-bonded analogues were almost identical to the superposition of the absorption of reactants. Additionally, in contrast to the individual haloforms, halogen bonding caused the NMR signal of haloform protons to shift to lower ppm values, whereas hydrogen bonding of CHX3 with aliphatic amines caused a shift in the opposite direction. Haloforms’ NMR spectra showed conflicting results when aromatic amines and hydrogen bonds were combined. While calculations of these pairs produced multiple hydrogen-bonded minima with comparable structures and energies but opposite directions of the NMR signals’ shifts, titration of all CHX3 with these nucleophiles consistently shifted the protons’ signals to lower ppm values. The formation constants of a few halogen- and hydrogen-bonded complexes between coexisting haloforms and amines in solutions were evaluated using experimental and computational data.

Keywords: halogen bonding; hydrogen bonding; haloforms; Amines; NMR spectroscopy; UV–Vis spectroscopy; DFT calculations; X-ray crystallography

Paper Quality: SCOPUS / Web of Science Level Research Paper

Subject: Chemistry

Writer Experience: 20+ Years

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