A multi-responsive system based on intramolecular B ← OP Lewis acid–base pairs

Abstract

A series of amino-triarylborane based flexible Lewis pairs with P(O)R2 (R = phenyl, methylphenyl) and BR2 (R = 2,4,6-trimethylphenyl (Mes), 2,6-dimethyl-4-methoxyphenyl (Mes(OMe)) were synthesized and fully characterized. These compounds display...

Photodissociative Modules that Control Dual‐Emission Properties in Donor–π–Acceptor Organoborane Fluorophores

“…The B•••O distance in 2 (1.602(2) Å) is shorter than those of the hitherto reported compounds A (1.630(2) Å) and C (1.643(2) Å). [22,24] The B•••S distance in P=S-coordinated 3 (2.104(6) Å) is much shorter than the sum (3.45 Å) of the van der Waals radii of the boron and sulfur atom. Due to the intramolecular P=X•••B coordination, the boron center adopts a tetrahedral structure, wherein the sum of the bond angles around the boron atom is 340.8°for 2 and 340.7°for 3, with a tetrahedral character of their boron centers of 61.8 % and 66.9 %, respectively.…”

“…[22] The other possible motif is a five-membered ring structure produced in an ortho-P=O-substituted phenylborane, which has been corroborated by the X-ray crystallographic analysis of compound B (Figure 1b). [23] Recently, Wang and coworkers have employed this motif as a spacer moiety in Dπ-A fluorophore C. [24] Importantly, both A and C underwent dissociation or variation in the degree of the P=O•••B coordination in the ground state, but not the excited state, in response to a change in the solvent polarity or temperature. Herein, we employ an ortho-P(=X)R 2 -substituted phenyl group as a module to impart triarylborane-based D-π-A fluorophores with responsiveness to multiple stimuli or environmental parameters (Figure 1a).…”

Multicolor Adjustable B–N Molecular Switches: Simple, Efficient, Portable, and Visual Identification of Butanol Isomers

“…Obviously, the number of valence electrons of the B is smaller than the number of valence orbitals, thus exhibiting an electron-deficient nature, − This favors the formation of coordination compounds (complexes) of boron. For example, in an sp 2 hybrid covalent molecule, the remaining p z empty orbital of the B can act as a Lewis acid, accepting an external lone pair of electrons (X: oxygen (O), nitrogen (N), phosphorus (P)) to form an sp 3 hybrid tetrahedral complex (Lewis acid–base pair). , Therefore, this Lewis acid complex generally has additivity, such as boron trifluoride and ammonia gas molecules forming B ← N Lewis acid–base pair. ,, However, this B ← X complex is usually in a metastable state, such as when its surrounding environment (such as T, P, and L) changes, its B ← X bond is prone to breakage or bond formation, thereby releasing different photophysical properties. ,− Therefore, rational design and utilization of the metastable structure of the B ← X complex is expected to successfully construct novel fluorescent molecular switches.…”

“…For example, in an sp 2 hybrid covalent molecule, the remaining p z empty orbital of the B can act as a Lewis acid, accepting an external lone pair of electrons (X: oxygen (O), nitrogen (N), phosphorus (P)) to form an sp 3 hybrid tetrahedral complex (Lewis acid−base pair). 27,28 Therefore, this Lewis acid complex generally has additivity, such as boron trifluoride and ammonia gas molecules forming B ← N Lewis acid−base pair. 27,29,30 However, this B ← X complex is usually in a metastable state, such as when its surrounding environment (such as T, P, and L) changes, its B ← X bond is prone to breakage or bond formation, thereby releasing different photophysical properties.…”

Internal B ← O Bond Facilitated Photo/Thermal Isomerization of Tetra-Coordinated Boranes

“…Boron-containing compounds have been demonstrated to be an important class of functional materials. Owing to the unique electron-deficient character and Lewis acidity of the boron atom, these types of compounds display a plethora of applications in numerous fields, including but not restricted to optoelectronic devices, − stimuli-responsive materials, − and catalysts. − In particular, several recent reports unveil that boron-based systems can undergo unusual molecular transformation under mild conditions, − opening a new avenue for the quantitative synthesis of functional boron heterocycles and thus attracting continuous research attention. − …”