To establish a detailed reaction mechanism for the condensation between a boronic acid, RB(OH)2, and a diol, H2L, in aqueous solution, the acid dissociation constants (Ka(BL)) of boronic acid diol esters (HBLs) were determined based on the well-established concept of conditional formation constants of metal complexes. The pKa values of HBLs were 2.30, 2.77, and 2.00 for the reaction systems, 2,4-difluorophenylboronic acid and chromotropic acid, 3-nitrophenylboronic acid and alizarin red S, and phenylboronic acid and alizarin red S, respectively. A general and precise reaction mechanism of RB(OH)2 with H2L in aqueous solution, which can serve as a universal reaction mechanism for RB(OH)2 and H2L, was proposed on the basis of (a) the relative kinetic reactivities of the RB(OH)2 and its conjugate base, that is, the boronate ion, toward H2L, and (b) the determined pKa values of HBLs. The use of the conditional formation constant, K', based on the main reaction: RB(OH)2 + H2L (K1)⇌ RB(L)(OH)(-) + H3O(+) instead of the binding constant has been proposed for the general reaction of uncomplexed boronic acid species (B') with uncomplexed diol species (L') to form boronic acid diol complex species (esters, BL') in aqueous solution at pH 5-11: B' + L' (K')⇌ BL'. The proposed reaction mechanism explains perfectly the formation of boronic acid diol ester in aqueous solution.

Oligoacenes are of interest as organic p-type semiconductors for use in electronic devices, but their use as n-type semiconductors is limited. N-Heteroacenes have been investigated as oligoacene-based n-type semiconductors due to their enhanced electron affinity. Herein, we report the synthesis, X-ray crystal structures, electrochemical, and field-effect transistor properties of TANC and BTANC.

A detailed kinetic study of the reactions of phenylboronic acid (PhB(OH) 2 ), 2-methylphenylboronic acid (2-MePhB(OH) 2 ), 2-isopropylphenylboronic acid (2-i PrPhB(OH) 2 ), and 1-hydroxy-3H-2,1-benzoxaborole (BxB(OH)) with D-fructose was carried out to clarify the nature of the reactive boron species in D-fructose sensing and investigate the corresponding reaction mechanism. Both the boronic acids (RB(OH) 2 ) and boronate ions (RB(OH) 3 À ) were reactive toward D-fructose, while out of the five D-fructose anomers only a-D-fructofuranose was reactive toward boron species. The reactions of all substrates proceeded consecutively in two steps (steps 1 and 2).We concluded that the first intermolecular step (step 1) corresponds to the parallel reactions (two parallel reactions for 2-i PrPhB(OH) 2 and three for the other systems) of the boronic acid and the boronate ion with a-D-fructofuranose to form bicoordinate complexes (mixture of exo-and endo-isomers), and the second intramolecular step (step 2) corresponds to the formation of a tricoordinate a-D-fructofuranose complex from the bicoordinate complexes. It was found that both the boronic acid and the boronate ion were kinetically reactive toward Dfructose, with the latter being more reactive.

Fundamental information on the reactivities of boronic acids toward catechols in aqueous solution is required in all the fields dealing with boronic acid. However, comprehensive studies on reactivity are often hindered by so-called "proton ambiguity," which makes it impossible for the rate constants of boronic acid and boronate ion to be determined separately. Herein, we set up two reaction systems without proton ambiguity: (1) Alizarin Red S and (2) Tiron with several boronic acids (RB(OH) 2 ) with different pK a s and performed kinetic and equilibrium studies on the reaction systems. It was shown that the logarithms of the rate constants of RB(OH) 2 and its conjugate boronate ion (RB(OH) 3 − ) decreased and increased linearly, respectively, with increasing pK a of RB(OH) 2 for both systems. Consequently, the reactivities of RB(OH) 2 and RB(OH) 3− were reversed at high RB(OH) 2 pK a . It was also shown that the bulky o − substituents of phenylboronic acids retarded the backward reactions, resulting in enhancement of the formation constants of boronic acid-catechol esters.