Mechanofluorochromic behaviors and data security protection properties of salicylaldimine-based difluoroboron complexes with different aryl substituents

To further explore the relationship between aryl substituents and mechanofluorochromic (MFC) behaviors, four salicylaldimine-based difluoroboron complexes (ts-Ph BF2, ts-Ph-NA BF2, ts-2NA BF2, and ts-triphenylamine [TPA] BF2), including aromatic substituents with different steric hindrance effects, were designed and successfully synthesized. Four complexes with twisted molecular conformation displayed intramolecular charge transfer and aggregation-induced emission properties. Under external mechanical stimuli, the as-synthesized powders of ts-Ph BF2, ts-Ph-NA BF2, and ts-TPA BF2 exhibited redshift fluorescence emission behaviors, and ts-Ph BF2 and ts-TPA BF2 could be recovered to original shifts by fuming, but ts-Ph-NA BF2 displayed irreversible switching. ts-2NA BF2 had no change during the grinding and fuming processes. The results indicated that the MFC behaviors could be attributed to the phase transformation between the well-defined crystalline and disordered amorphous states by X-ray diffraction measurement. Further research illustrated that ts-TPA BF2 with the most significant MFC phenomenon could be applied in data security protection in ink-free rewritable paper.

Advances in the Supramolecular Chemistry of Tetracoordinate Boron-Containing Organic Molecules into Organogels and Mesogens

Boron-containing organic compounds are well accepted as a class of compounds having excellent photophysical properties. In addition to the unique photophysical properties, the ease of synthesis and structural robustness make tetracoordinate boron complexes ideal for a variety of applications. While significant light has been thrown on their luminescence properties, there is no collective attention to their supramolecular chemistry. In this mini review, we discuss the progress made in the supramolecular chemistry of these compounds which includes their utility as building blocks for liquid crystalline materials and gels largely driven by various non-covalent interactions like H-bonding, CH-π interactions, BF-π interactions and Van der Waals forces. The organoboron compounds presented here are prepared from easy-to-synthesize chelating units such as imines, diiminates, ketoiminates and diketonates. Moreover, the presence of heteroatoms such as nitrogen, oxygen and sulfur, and the presence of aromatic rings facilitate non-covalent interactions which not only favor their formation but also helps to stabilize the self-assembled structures.

Pteridine derivatives: novel low-molecular-weight organogelators and their piezofluorochromism

Here, π-conjugated compounds based on pteridine derivatives were synthesized and their self-assembling behaviors in a variety of organic solvents and piezofluorochromism were studied.

Mechanofluorochromic behaviors of triphenylamine functionalized salicylaldimine difluoroboron complexes

The solid-state emission of D–A type difluoroboron complexes is tuned by external forces.

Effect of a bridge unit on the mechanochromism of phenothiazine-based Schiff bases

Phenothiazine Schiff base PPD bridged with a rigid p-phenylenediamine unit showed a reversible mechanofluorochromism, while the one with ethylenediamine did not change its fluorescence after grinding.

H- and J-aggregates formed from a nontraditional π-gelator depending on the solvent polarity for the detection of amine vapors

A tert-butyl carbazole-modified difluoroboron β-diketonate complex (TCbzB) has been synthesized. Although no traditional gelation group was involved in TCbzB, it could form organogels in the mixed solvents of o-dichlorobenzene/cyclohexane (v/v = 1/5 or 1/2), toluene/cyclohexane (v/v = 1/2) and chlorobenzene/cyclohexane (v/v = 1/2). Interestingly, an orange organogel was obtained in o-dichlorobenzene/cyclohexane (v/v = 1/2) with relatively high polarity and red organogels were gained in the other three mixed solvents with relatively low polarity. TCbzB self-assembled into H-aggregates and J-aggregates in orange and red organogels, respectively, and the corresponding xerogels emitted yellow and red light, respectively, under UV illumination. The red emission of the xerogel-based film could be quenched significantly by gaseous n-propylamine and aniline because of the decomplexation of the difluoroboron β-diketonate complex by n-propylamine and the weak interactions between aniline and boron difluoride units.

Pyrimidine-containing β-iminoenolate difluoroboron complexes acting as non-traditional π-gelators and mechanofluorochromic dyes

A xerogel-based film based on a mechanofluorochromic dye of a β-iminoenolate difluoroboron complex could detect TFA vapor with high performance.

Diarylethene-based xerogels: the fabrication of more entangled networks driven by isomerization and acidofluorochromism

The organogels were formed from fully-conjugated styrylbenzoxazoles and styrylbenzothiazoles without traditional gelation groups.

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

The synthesis, spectroscopic properties, and in vitro cytotoxicity activity of a series of various salen-based triboron complexes have been designed and prepared from hemi-salen (L₁ H₃  - L₄ H₃ ) ligands and BF₃ ·Et₂ O or BPh₃ under simple reaction conditions. The hemi-salen (L₁ H₃  - L₄ H₃ ) ligands and their BF₂ or BPh₂ chelating triboron complexes were characterized by means of NMR (¹ H, ¹³ C, ¹⁹ F, and ¹¹ B) spectra, FT-IR spectra, UV/VIS spectra, fluorescence spectra, mass spectra, melting point, as well as elemental analysis. The triboron [L_(1 - 4) (BF₂ )₃ ] and [L_(1 - 4) (BPh₂ )₃ ] complexes were investigated for their absorption and emission properties, and these complexes are also good chelates towards boron(III) fragments such as BF₂ or BPh₂ quantum yield in solution reaching up to 38%. The hemi-salen (L₁ H₃  - L₄ H₃ ) ligands and their BF₂ or BPh₂ chelating triboron complexes were tested for the in vitro anticancer activity against various cancer and normal cells (HeLa, DLD-1, ECC-1, PC-3, PNT-1A, and CRL-4010), and it was found that the cell viability of cancer cells was decreased while most of the healthy cells could still be viable. Also, the cytotoxicity studies showed that anticancer activity of hemi-salen (L₁ H₃  - L₄ H₃ ) ligands is higher than that of triboron [L_(1 - 4) (BF₂ )₃ ] and [L_(1 - 4) (BPh₂ )₃ ] complexes. The hemi-salen (L₁ H₃  - L₄ H₃ ) ligands showing the strongest cytotoxic effect in PC-3 cells were found to exhibit anticancer activity with apoptosis by increasing the level of ROS in the PC-3 cells.