Novel Non-Metal Cation (NMC) Pentaborate Salts of Some Amino Acids

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 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.

Zwitterionic amino acids as precursors for nonmetal cation pentaborate salts

“…The stress peaks of the -O-H groups, which can be interpreted as other characteristic peaks of the pentaborate structures, also appeared in 3,387, 3,380, 3,379, and 3,446 cm −1 regions, respectively, in the order of molecules. [24,26,39]…”

“…Pentaborates contain anionic trigonal BO 3 and related tetragonal BO 4 − structures. [24,26] Hexaborates contain anionic trigonal BO 3 and the associated tetragonal BO 4…”

“…Pentaborates contain anionic trigonal BO 3 and related tetragonal BO 4 − structures. [ 24,26 ] Hexaborates contain anionic trigonal BO 3 and the associated tetragonal BO 4 − , as well as excessive trigonal B(OH) 3 . When poraborate anions stabilized by the metal cation contain metal cation‐free compounds as stabilizing ions, more porous and channeled compounds are obtained.…”

“…[23,24] This electronic and steric factor remarkably influences the structure of the NMC borate compounds. [24][25][26][27] The structure of pentaborate (−1) with or without metal cation is highly stable and is converted into a cyclic structure by the polymerization reaction resulting from the water outflow in basic aqueous solutions (i.e., containing -OH − ions). [28][29][30][31][32] NMC hexaborates are formed through the reaction of excessive amounts of boric acid.…”

“…Recently, some metal cation/anion pentaborate salts mentioned in the literature have been investigated structurally. [24][25][26][27]32,34,38] In this study, pentaborate structures were synthesized using protonated tryptophan, methionine, lysine, and phenylalanine amino acids as cations. The newly synthesized molecules were characterized by chemical composition analysis, fourier-transform infrared spectroscopy (FT-IR), mass analysis, boron nuclear magnetic resonance ( 11 B-NMR), powder X-Ray Diffraction (XRD), and thermal gravimetric analysis (TGA/DTA) methods.…”