Tuning of the colour and chemical stability of model boranils: a strong effect of structural modifications

Abstract

A series of diarylborinic complexes with salicydeneaniline ligands bearing various functional groups at the 6-position have been synthesized in high yields by applying a straightforward one-pot multicomponent protocol. UV-Vis measurements revealed the influence of electronic character of substituents on the observed maximum of emission (λem). This has been confirmed by a relatively strong linear correlation (R(2) = 0.92) of λem with Hammett σp(+) constants. Such a correlation was investigated using a QTAIM analysis of the charge density distribution. Absorption and emission bands for the obtained systems span between 390-437 nm and between 506-590 nm, respectively, with quantum yields reaching 17%. Time-dependent UV-Vis absorption measurements revealed that diphenylborinic salicydeneaniline complexes undergo slow degradation in solution under ambient conditions. In contrast, the use of a naphthalene-based chromophore or the introduction of fluorinated phenyl groups at the boron atom resulted in stable systems.

Iodo‐Functionalized Salicylideneimine‐Boron Complexes: Synthesis and Photosensitized Degradation of Organic Water Pollutants

“…As shown in Figure S11 (in the Supporting Information), we observed significant photobleaching for 1 – 3 under our experimental conditions whereas negligible changes were observed in the absorption spectrum of 4 upon irradiation, thereby indicating its excellent photostability. It is reported that boranils are prone to deboronation . On a similar note, the observed changes in the absorption spectra could be attributed to the elimination of the BF 2 moiety, resulting in the formation of the corresponding imines.…”

“…It is reported that boranils are prone to deboronation. [28,40] On as imilar note, the observed changes in the absorption spectra could be attributed to the elimination of the BF 2 moiety,r esulting in the formation of the corresponding imines. Furtherd etailed investigationsare necessary to ascertain the mechanism of this photochemical process.…”

“…The overlap of the empty p‐orbital of boron with the organic moieties in such compounds leads to the delocalization of the electron cloud and planarization of the π‐systems, thereby resulting in interesting photophysical properties. Several tri‐ and tetra‐coordinated boron compounds have been synthesized by the complexation of boron with organic ligands containing hetero atoms . Four‐coordinate boron compounds based on an imine scaffold are reported to have higher stability compared with tricoordinate boron compounds .…”

“…Severalt ri-andt etra-coordinated boron compounds have been synthesized by the complexation of boron with organic ligands containing hetero atoms. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] Fourcoordinate boronc ompounds based on an imine scaffold are reported to have higher stabilityc ompared with tricoordinate boron compounds. [18] Although the luminescentp roperties of boranils are well documented, [18] the photosensitizationp rop-ertieso fs uch molecules have rarely been explored.…”

A stress tensor and QTAIM perspective on the substituent effects of biphenyl subjected to torsion

“…This includes, in particular, the work of Popelier who used a similarity measure in the form of a BCP (bond critical point) space to accurately predicted the Hammett σ p and σ m values for benzoic acids . Other more recent work has also provided QTAIM perspectives on Hammett constants …”