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Conformational Polymorphism in N ‐(4′‐methoxyphenyl)‐ 3‐bromothiobenzamide
Author(s) -
Bashkirava Anastasiya,
Andrews Philip C.,
Junk Peter C.,
Robertson Evan G.,
Spiccia Leone,
Vanderhoek Nafty
Publication year - 2007
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200600410
Subject(s) - crystallography , raman spectroscopy , intermolecular force , differential scanning calorimetry , chemistry , molecule , polymorphism (computer science) , crystal structure , crystal (programming language) , planarity testing , infrared spectroscopy , spectroscopy , organic chemistry , biochemistry , physics , programming language , gene , genotype , computer science , optics , thermodynamics , quantum mechanics
Three conformational polymorphs of N ‐(4′‐methoxyphenyl)‐3‐bromothiobenzamide, yellow α, orange β, and yellow γ, have been identified by single‐crystal X‐ray diffraction. The properties and structure of the polymorphs were examined with FT Raman, FTIR (ATR), and UV/Vis spectroscopy, as well as differential scanning calorimetry. Computational data on rotational barriers in the isolated gas‐phase molecule indicate that the molecular conformation found in the α form is energetically preferred, but only by around 2 kJ mol −1 over the γ conformation. The planar molecular structure found in the β form is destabilized by 10–14 kJ mol −1 , depending on the calculation method. However, experimental evidence suggests that the β polymorph is the most stable crystalline phase at room temperature. This is attributed to the relative planarity of this structure, which allows more and stronger intermolecular interactions, that is, more energetically effective packing. Calculated electronic‐absorption maxima were in agreement with experimental spectra.