Synthesis and Optical Properties of Salicylaldimine‐Based Diboron Complexes

Abstract

New salicylaldimine-based diboron complexes 1-3 have been synthesized and characterized by multinuclear NMR spectroscopy, mass spectrometry, and single-crystal X-ray analysis (1 and 3). The photophysical and electrochemical

Theoretical and experimental investigations of complexation with BF3.Et2O effects on electronic structures, energies and photophysical properties of Anil and tetraphenyl (hydroxyl) imidazol

“…As predictable, both of the 19 F spectrum of (b) and (d) boron complexes show two clear signs found respectively at −148.41 ppm −148.35 ppm as doublet signal and at −137.21 ppm and − 137.15 ppm as a doublet signal too. These resonances are solid evidence of the chelation of BF 2 group and the formation of the desired compounds as recently reported in some boron difluoride complexes . The absence of quartets in our 19 F NMR spectra brings to light the fast relaxation of the quadrupolar boron nuclei at room temperature .…”

“…Attention has recently increased in last decencies on four coordinate organoboron compounds as outstanding fluorescent dyes . Those luminescent fluorophors are useful tools owing to their potential applications in numerous fields such as organic light emitting diodes (OLEDs), pH sensors, visualizing biologic phenomenon, anion detection, artificial light tent, use in electroluminescent devices, as fluorescent light−emitting materials and as fluorescent sensors . With advances in those fields, researchers are continually trying to synthesize different boron fluorophores; conjugated tetracoordinate diboron or multiboron systems to ameliorate and explore the several exploitations mentioned above.…”

Synthesis and Characterization of the Hemi‐Salen Ligands and Their Triboron Complexes: Spectroscopy and Examination of Anticancer Properties

“…Further evidence for the formation of the salen ligands ( L 1 H 3 – L 4 H 3 ) and their triboron [L 1 – 4 (BF 2 ) 3 ] and [ L 1 – 4 (BPh 2 ) 3 ] complexes were obtained from the 1 H‐NMR, 13 C‐NMR, 19 F‐NMR, and 11 B‐NMR spectra (see Supporting Information and Figures S5 – S11). The 1 H‐NMR signals belonging to the OH protons are readily distinguishable and the disappearance of the downfield H‐bonded OH protons ( δ (H) ≈ 13 – 15 ppm) of the salen type ( L 1 H 3 – L 4 H 3 ) gives the first indication for the formation of triboron complexes [ ][ ] and also the disappearance of the readily distinguishable OH protons confirm the binding of the boron atoms to the oxygen. The proton peaks of the azomethine groups in fluorine triboron complexes [L 1 – 4 (BF 2 ) 3 ] (at range δ (H) 8.92 – 8.53 ppm) and phenyl triboron complexes [L 1 – 4 (BPh 2 ) 3 ] (at range δ (H) 9.06 – 8.04 ppm) are significantly shifted to the low or high field in comparison with those of the formed hemi‐salen ligands ( L 1 H 3 – L 4 H 3 ) (at range δ (H) 9.08 – 8.26 ppm), resulting from the electron deficient/electron excess nature of BF 2 or BPh 2 moiety.…”

“…In the 11 B‐NMR spectra of the fluorine [L 1 – 4 (BF 2 ) 3 ] and phenyl [L 1 – 4 (BPh 2 ) 3 ] triboron complexes, only one boron signal was observed in the range of δ (B) −0.92 to −0.98 ppm for fluorine triboron [L 1 – 4 (BF 2 ) 3 ] complexes and in the range of δ (B) 1.09 to 1.16 ppm for phenyl triboron [L 1 – 4 (BPh 2 ) 3 ] complexes due to the same chemical environment for the three boron atoms of each compound ( Figures and ), which confirms the formation of four‐coordinate N , O ‐chelated triboron complexes [ ][ ] and indicates N→B bonds to be predominant in (D 6 )DMSO solution. However, the fluorine [L 1 – 4 (BF 2 ) 3 ] and phenyl [L 1 – 4 (BPh 2 ) 3 ] triboron complexes showed different chemical resonances in 11 B‐NMR spectra, suggesting the alteration of electronic properties because of the presence of the various electron withdrawing/donor groups on the aromatic ring in triboron complexes ( Figure ).…”

“…The absence of quartet s in the 19 F‐NMR spectra reveals that there may be a fast relaxation of the quadrupolar boron nuclei at room temperature ( Figure ). [ ][ ]…”