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Special Issue "Polyborates: Applications, Synthesis, and Structural and Physical Properties"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Inorganic Chemistry".

Deadline for manuscript submissions: closed (31 December 2019).

Special Issue Editor

Prof. Dr. Michael A. Beckett
E-Mail Website
Guest Editor
School of Natural Sciences, Bangor University, Bangor, LL57 2UW, UK
Interests: agricultural bio-stimulants; boron-11 NMR; computational studies; hydrogen bonding; Lewis acidity measurement; organoborates and silicates; polyborates and silicates; synthesis; supramolecular self-assembly; transition-metal chemistry

Special Issue Information

Dear Colleagues,

Polyborates are a class of inorganic compound (salt) containing boron atoms within their anionic moieties. These boron atoms are bound solely to oxygen and can adopt either trigonal-planar or tetrahedral connectivity. The cations of these salts can be ‘naked’ metals (e.g. Na+), organic, or transition-metal complexes and furthermore, polyborates may also be anhydrous or hydrated. Consequentially, polyborates show immense solid-state structural diversity with ‘hydrogen-bonded insular systems’ and ‘supramolecular polymeric systems’ well represented within the class. Polyborates have unique properties and a few (e.g. Na2[B4O5(OH)4].3H2O = Na2B4O7.5H2O, ‘borax pentahydrate’) have been used in the production of a wide variety of bulk products such as insulation fiberglass, specialty glasses, enamels and glazes, fertilizers, biocides, fire retardants, detergents. The polyborates β-BaB2O4 and LiB3O5 are well-known for their interesting non-linear optical (NLO) second-harmonic generation properties and NLO properties of other polyborates have also been investigated. Other interesting spectroscopic properties e.g optical absorption (UV/VIS), fluorescence, photoluminescence, have been observed and these may lead to future applications. The intent of this Special Issue is to focus on the most recent advances in polyborate chemistry ranging from fundamental aspects to current and potential applications. Full papers, communications, and reviews on these topics are welcome.

Prof. Dr. Michael A. Beckett
Guest Editor

Manuscript Submission Information

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Keywords

  • Polyborate chemistry
  • Applications
  • Computational studies
  • Physical and thermal properties
  • NLO properties
  • Solid-state structural studies
  • Solution equilibria
  • Spectroscopic behaviour
  • Synthetic methods

Published Papers (4 papers)

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Research

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Open AccessArticle
Pentaborate(1-) Salts and a Tetraborate(2-) Salt Derived from C2- or C3-Linked Bis(alkylammonium) Dications: Synthesis, Characterization, and Structural (XRD) Studies
Molecules 2020, 25(1), 53; https://doi.org/10.3390/molecules25010053 - 23 Dec 2019
Abstract
The synthesis of a number of pentaborate(1-) salts from cations arising from N-substituted α,α-, α,β-, and α,γ-diaminoalkanes has been attempted in aqueous solution from B(OH)3 and the appropriate diammine in a 10:1 ratio. Despite relatively mild work-up conditions the pentaborate(1-) salts [...] Read more.
The synthesis of a number of pentaborate(1-) salts from cations arising from N-substituted α,α-, α,β-, and α,γ-diaminoalkanes has been attempted in aqueous solution from B(OH)3 and the appropriate diammine in a 10:1 ratio. Despite relatively mild work-up conditions the pentaborate(1-) salts prepared were not always as anticipated and the following compounds were isolated in good yield: [Me2NH(CH2)2NHMe2][B5O6(OH)4]2 (1), [Et2NH(CH2)2NHEt2][B5O6(OH)4]2 (2), [Et2NH2][B5O6(OH)4] (3), [Me2NH2][B5O6(OH)4] (4), [Me2NH(CH2)3NHMe2][B5O6(OH)4]2 (5), [Et2NH(CH2)3NHEt2][B5O6(OH)4]2 (6), [Me3NCH2CH=CH2][B5O6(OH)4] (7), and [Me3N(CH2)3NMe3] [B5O6(OH)4]2.0.5H2O (8). The tetraborate(2-) salt, [Me3N(CH2)2NMe3][B4O5(OH)4].2B(OH)3.2H2O (9) was obtained in moderate yield (41%) from a 3:1 reaction of B(OH)3 with [Me3N(CH2)2NMe3](OH)2. All compounds were characterized by spectroscopy (1H, 11B, 13C NMR and IR) and thermal gravimetric analysis (TGA). BET analysis on materials derived thermally from selected samples (1, 2, 6, 7) all had porosities of < 1 m2/g, demonstrating that they were non-porous. Single-crystal XRD structures were obtained for 2, 3, 7, 8 and 9 and all contain extensive H-bonded polyborate lattices. Full article
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Open AccessFeature PaperArticle
Novel Non-Metal Cation (NMC) Pentaborate Salts of Some Amino Acids
Molecules 2019, 24(15), 2790; https://doi.org/10.3390/molecules24152790 - 31 Jul 2019
Abstract
Non-metal cation (NMC) pentaborate structures, in which some amino acids (valine, leucine, isoleucine, and threonine) were used as cations, were synthesized. The structural characterization of molecules was carried out by elemental analysis, FT-IR, mass, 11B-NMR, and thermal analysis (TGA/DTA) methods. The hydrogen [...] Read more.
Non-metal cation (NMC) pentaborate structures, in which some amino acids (valine, leucine, isoleucine, and threonine) were used as cations, were synthesized. The structural characterization of molecules was carried out by elemental analysis, FT-IR, mass, 11B-NMR, and thermal analysis (TGA/DTA) methods. The hydrogen storage capacity of molecules was also calculated by taking experimental results into consideration. The FT-IR spectra support the similarity of structures. The characteristic peaks attributable to pentaborate rings and amino acids were observed. When thermal analysis data were examined, it was observed that pentaborate salts gave similar degradation steps and degradation products. As a final degradation product of all thermal analysis experiments, a glassy form of B2O3 was observed. The valine pentaborate is the most thermally stable. Also, the amounts of hydrate water outside the coordination sphere of the compounds were determined by thermal analysis curves. The peaks of boric acid, triborate, and pentaborate structures were obtained in ppm with the 11B-NMR results of synthesized pentaborate compounds. With powder X-ray spectroscopy, all structures were found to be crystalline but not suitable for single-crystal X-ray analysis. The molecular cavities of the compounds detected by BET were found to be 3.286, 1.873, 2.309, and 1.860 g/cm3, respectively. A low number of molecular cavities can be interpreted in several existing hydrogen bonds in structures. The hydrogen storage capacities of the molecules were found to be in the range of 0.04 to 0.07% by mass. Full article
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Review

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Open AccessReview
Research and Development of Zincoborates: Crystal Growth, Structural Chemistry and Physicochemical Properties
Molecules 2019, 24(15), 2763; https://doi.org/10.3390/molecules24152763 - 30 Jul 2019
Abstract
Borates have been regarded as a rich source of functional materials due to their diverse structures and wide applications. Therein, zincobrates have aroused intensive interest owing to the effective structural and functional regulation effects of the strong-bonded zinc cations. In recent decades, numerous [...] Read more.
Borates have been regarded as a rich source of functional materials due to their diverse structures and wide applications. Therein, zincobrates have aroused intensive interest owing to the effective structural and functional regulation effects of the strong-bonded zinc cations. In recent decades, numerous zincoborates with special crystal structures were obtained, such as Cs3Zn6B9O21 and AZn2BO3X2 (A = Na, K, Rb, NH4; X = Cl, Br) series with KBe2BO3F2-type layered structures were designed via substituting Be with Zn atoms, providing a feasible strategy to design promising non-linear optical materials; KZnB3O6 and Ba4Na2Zn4(B3O6)2(B12O24) with novel edge-sharing [BO4]5− tetrahedra were obtained under atmospheric pressure conditions, indicating that extreme conditions such as high pressure are not essential to obtain edge-sharing [BO4]5−-containing borates; Ba4K2Zn5(B3O6)3(B9O19) and Ba2KZn3(B3O6)(B6O13) comprise two kinds of isolated polyborate anionic groups in one borate structure, which is rarely found in borates. Besides, many zincoborates emerged with particular physicochemical properties; for instance, Bi2ZnOB2O6 and BaZnBO3F are promising non-linear optical (NLO) materials; Zn4B6O13 and KZnB3O6 possess anomalous thermal expansion properties, etc. In this review, the synthesis, crystal structure features and properties of representative zincoborates are summarized, which could provide significant guidance for the exploration and design of new zincoborates with special structures and excellent performance. Full article
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Open AccessReview
Hydrated Zinc Borates and Their Industrial Use
Molecules 2019, 24(13), 2419; https://doi.org/10.3390/molecules24132419 - 30 Jun 2019
Cited by 1
Abstract
Zinc borates are important chemical products having industrial applications as functional additives in polymers, bio-composites, paints and ceramics. Of the thirteen well documented hydrated binary zinc borates, Zn[B3O4(OH)3] (2ZnO∙3B2O3∙3H2O) is manufactured [...] Read more.
Zinc borates are important chemical products having industrial applications as functional additives in polymers, bio-composites, paints and ceramics. Of the thirteen well documented hydrated binary zinc borates, Zn[B3O4(OH)3] (2ZnO∙3B2O3∙3H2O) is manufactured in the largest quantity and is known as an article of commerce as 2ZnO∙3B2O3∙3.5H2O. Other hydrated zinc borates in commercial use include 4ZnO∙B2O3∙H2O, 3ZnO∙3B2O3∙5H2O and 2ZnO∙3B2O3∙7H2O. The history, chemistry, and applications of these and other hydrated zinc borate phases are briefly reviewed, and outstanding problems in the field are highlighted. Full article
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