Synthesis, Characterization, and Complexation of Tetraarylborates with Aromatic Cations and Their Use in Chemical Sensors

Abstract

Five aromatic borate anions, namely tetrakis(4-phenoxyphenyl)borate (1), tetrakis(biphenyl)borate (2), tetrakis(2-naphthyl)borate (3), tetrakis(4-phenylphenol)borate (4), and tetrakis(4-phenoxy)borate (5), have been prepared and tested as ion-recognition sites in chemical sensors for certain aromatic cations and metal ions. To gain further insight into the complexation of the cations, some complexes have been prepared and structurally characterized. The complexation behavior of 1 and 2 towards N-methylpyridinium (6), 1-ethyl-4-(methoxycarbonyl)pyridinium (7), tropylium (8), imidazolium (9), and 1-methylimidazolium (10) cations has been studied, and the stability constants of the complexes of 1 with cations 6 and 8 have been measured to compare them with the values for the previously studied complexes of tetraphenylborate. The structures of the borate anions and their complexes have been characterized by NMR and mass spectrometric methods. X-ray crystal structures have been determined for potassium tetrakis(4-phenoxyphenyl)borate (K(+)1), N-methylpyridinium tetrakis(4-phenoxyphenyl)borate (61), 1-ethyl-4-(methoxycarbonyl)pyridinium tetrakis(4-phenoxyphenyl)borate (71), tropylium tetrakis(4-phenoxyphenyl)borate (81), and imidazolium tetrakis(biphenyl)borate (92). The results show that borate derivatives are potential candidates for a completely new family of charged carriers for use in cation-selective electrodes.

Sodium Tetraalkoxyborates: Intermediates for the Quantitative Reduction of Aldehydes and Ketones to Alcohols through Ball Milling with NaBH4

“…These very-high-melting, stable solids with extreme sensitivity towards hydrolysis are regiospecifically formed and can be of practical use for the chemisorption of gases up to the purification of inert gases from trace impurities, [30] for chemical sensors (ion-recognition sites), [19] and for industrial purposes such as their use as polymerization catalysts. [31] Further uses of hitherto not reasonably available salts 3 do suggest themselves.…”

“…[4] Other methods for the production of tetraalkoxyborates are the tedious addition of metal alkoxylates to boric acid esters in the respective alcohol, [17] or the alcohol exchange of tetraalkoxyborates. [18] Phenols and NaBH 4 (2) react to give related tetraaryloxyborates in THF, [19] or as a result of their low hydrolytic sensitivity, by reaction of boric acid with phenols. [20] …”

Electrochemical Sensors

“…12 While the selectivity differences among various ion-exchangers amounted to about one order of magnitude, the results show again that the structure of the ion-exchanger may play a significant role in the ion recognition process if no other ionophore is present in the membrane.…”

Tetra(p‐tolyl)borate‐Functionalized Solvent Polymeric Membrane: A Facile and Sensitive Sensing Platform for Peroxidase and Peroxidase Mimetics

“…[18] In contrast, o-PD intermediates are mainly mono-A C H T U N G T R E N N U N G cationic under the employed conditions according to their pK a values for the second protonation (data not shown), thereby possessing much smaller ion association constants with counterions as compared with dications. [37,43] In addition to the high sensitivity and excellent reversibility, the present peroxidase detection method has other advantages. The SPM functionalized with a substituted tetraphenylborate show lower membrane resistance as compared with the previously used DNNS-doped membrane, [18,44] which yields smaller potential noises and facilitates its miniaturization.…”