Enhancing Electron Accepting Ability of Triarylboron via π-Conjugation with 2,2‘-Bipy and Metal Chelation:  5,5‘-Bis(BMes₂)-2,2‘-bipy and Its Metal Complexes

Abstract

Experimental General consideration: All reactions were performed under an inert atmosphere of dry N 2 with standard Schlenk techniques unless otherwise noted. All starting materials were purchased from Aldrich Chemical Co. and used without further purification. THF, Et 2 O, and CH 2 Cl 2 were purified using the solvent purification system (Innovation Technologies Co.). Deuterated solvents as chloroform-d 1 (D, 99.8%), methanol-d 4 (D, 99.8%), benzene-d 6 (D, 99.5%) and methylene chloride-d 2 (D, 99.9%) (Cambridge Isotopes) were used as received without further drying. NMR spectra were recorded on a Bruker Avance 400 spectrometer (400.13 MHz for 1 H, 100.62 MHz for 13 C, 376.50 MHz for 19 F), chemical shifts are referenced to the residual solvent peaks and have been reported in parts per million (ppm) relative to TMS (1 H and 13 C) and CFCl 3 (19 F). UV-Vis spectra were recorded on a Varian Cary-3 UV-Visible spectrophotometer. Cyclic voltammetry was performed using a BAS CV-50W analyzer with a scan rate of 500 mV/s to 4 V/s and a typical concentration of 5 mg of the compounds in 3 mL DMF. The electrolytic cell used was a conventional three-compartment cell, in which a Pt working electrode, a Pt auxiliary electrode, and a Ag/AgCl reference electrode were employed. The CV measurements were performed at room temperature using 0.10 M tetrabutylammonium hexafluorophosphate (TBAP) as the supporting electrolyte and DMF as the solvent. The ferrocenium/ferrocene couple was used as the internal standard (E 0 = 0.55 V). Elemental analyses were

A class of fascinating optoelectronic materials: Triarylboron compounds

“…The addition of F  to the solution of 49 causes a phosphorescent color switch from yellow to green, serving as a "naked-eye" indicator of F  . 19 [8,43,44]. For these complexes and the corresponding ligands containing BMes 2 groups, the electron-accepting ability or the Lewis acidity of the boron center could be significantly enhanced by metal chelation/ binding to a conjugate triarylboron ligand [8], and consequently the affinity of the boron center for F  would be increased, leading to the development of more sensitive and versatile sensing systems.…”

“…19 [8,43,44]. For these complexes and the corresponding ligands containing BMes 2 groups, the electron-accepting ability or the Lewis acidity of the boron center could be significantly enhanced by metal chelation/ binding to a conjugate triarylboron ligand [8], and consequently the affinity of the boron center for F  would be increased, leading to the development of more sensitive and versatile sensing systems. Wang et al [8] synthesized 51 and its Pt(II) complex 52 ( Figure 13) and examined the impact of metal chelation on Lewis acidity of 51.…”

“…With its vacant p  orbital, the boron center is inherently electron deficient and often acts as a strong -electron acceptor, which may lead to significant delocalization when conjugated with an adjacent organic -system [1] and is responsible for some excellent properties, such as the formation of charge-transfer states when accompanied by electron donors and highly efficient emission in both solution and solid states. These properties have permitted their potential uses for various photonic and optoelectronic applications, such as luminescent sensors for anions [6][7][8][9][10], emitters and charge-transport materials in organic light-emitting devices (OLEDs) [11][12][13][14][15], and twophoton excited emitters [16,17].…”

Optical and electronic properties of organoboron compounds in solvent

“…In order to improve the electron injecting and transporting properties in OLEDs, lower energy emission, and larger two-photon absorption cross sections and so on, many research groups looked for suitable organoboron compounds. However, most of these do not give sufficient steric protection to the boron centre to render it stable in air [12][13][14][15][16]. Marder et al prepared three compounds using phenyl (1), 4-(1,1-Dimethylethyl) phenol (2) and 4-N,N-diphenylaminophenyl (3) groups attached to bis(fluoromesityl)boryl ((FMes)2B) by B-C bonds [17].…”

Fluoride Sensing by Catechol‐Based π‐Electron Systems

“…[11,12] For the most widely studied NÀH containing sensing materials it has been proposed that the fluoride leads to deprotonation of the sensing molecule with the loss of the proton resulting in detectable changes in properties such as colour. [7] The advantages of using optical detection over methods such as nuclear magnetic resonance [13] and electrochemistry [14] are that it can provide high sensitivity, easy visualization, a fast response time, and can be incorporated into a handheld detector for field measurements. [15,16] Given the effort to develop materials with acidic NÀH protons for the detection of fluoride it is a little surprising that other protonic acids with suitable pK a s have not been investigated in more detail.…”