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Open AccessArticle

Structure and Properties of 1,3-Phenylenediboronic Acid: Combined Experimental and Theoretical Investigations

1
Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland
2
Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland
3
Adamed Pharma S.A., Pieńków, Adamkiewicza 6A, 05-152 Czosnów, Poland
4
Faculty of Chemistry, University of Gdańsk, Wita Stwosza 63, 80-308 Gdańsk, Poland
*
Author to whom correspondence should be addressed.
Crystals 2019, 9(2), 109; https://doi.org/10.3390/cryst9020109
Received: 16 January 2019 / Revised: 14 February 2019 / Accepted: 15 February 2019 / Published: 19 February 2019
(This article belongs to the Special Issue Novel Hydrogen-bonded Materials with Significant Physical Properties)
The structure and properties of 1,3-phenylenediboronic acid are reported. Molecular and crystal structures were determined by single crystal as well as by powder X-ray diffraction methods. Acidity constant, thermal behavior, and NMR characterization of the title compound were also investigated. In addition to the experimental data, calculations of rotational barrier and intermolecular interaction energies were performed. The compound reveals a two-step acid–base equilibrium with different pKa values. TGA and DSC measurements show a typical dehydration reaction with formation of boroxine. In crystals, hydrogen-bonded dimers with syn-anti conformation of hydroxyl groups form large numbers of ribbon motifs. The 2D potential energy surface scan of rotation of two boronic groups with respect to phenyl ring reveals that the rotation barrier is close to 37 kJ⋅mol−1, which is higher than the double value for the rotation of the boronic group in phenylboronic acid. This effect was ascribed to intermolecular interaction with C–H hydrogen atom located between boronic groups. Furthermore, the molecules in the crystal lattice adopt a less stable molecular conformation most likely resulting from intermolecular forces. These were further investigated by periodic DFT calculations supported by an estimation of dimer interaction energy, and also by topological analysis of electron density in the framework of AIM theory. View Full-Text
Keywords: boronic acid; 1,3-phenylenediboronic acid; crystal structure; DSC; TGA; acidity constant; rotation barrier; DFT; AIM boronic acid; 1,3-phenylenediboronic acid; crystal structure; DSC; TGA; acidity constant; rotation barrier; DFT; AIM
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Adamczyk-Woźniak, A.; Cyrański, M.K.; Durka, K.; Gozdalik, J.T.; Klimentowska, P.; Rusiecki, R.; Sporzyński, A.; Zarzeczańska, D. Structure and Properties of 1,3-Phenylenediboronic Acid: Combined Experimental and Theoretical Investigations. Crystals 2019, 9, 109.

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