Reunderstanding the Fluorescent Behavior of Four-Coordinate Monoboron Complexes Containing Monoanionic Bidentate Ligands

Abstract

We demonstrated for the first time that, at temperatures below the melting point of a given polar solvent, the emission of some four-coordinate monoboron complexes containing monoanionic bidentate (NO) ligands shifted to lower wavelengths, but no such shift was observed for studies conducted in nonpolar solvents. This means that the emission from a polar solvent appears at shorter wavelengths if compared with that from a nonpolar solvent when the measurement was performed at low temperatures, a phenomenon totally different from that observed for conventional solvatochromic fluorophores. The finding was rationalized by considering the temperature-dependent conformational relaxation of the tetrahedron monoboron complexes from their local excited (LE) state to their relaxed excited (RE) state. Further studies revealed that variating the structure of the chelating ligands could result in remarkable changes in the fluorescent colors of the monoboron complexes. However, changing the structure of other two monodentate ligands showed little effect upon the fluorescence property of the compounds. Therefore, it is anticipated that the monoboron complexes may be taken as a platform to construct a variety of functional molecular systems via alternating the structure of the chelating ligand and that of the monodentate ligand. As an example, naphthalene was introduced as a monodentate ligand, and independent emissions from naphthalene unit and the other part of the monoboron complex as well as intramolecular energy transfer between them were observed. It is believed that the present work provides a new insight into the monoboron complexes, laying the foundation for them to be explored for developing novel molecular systems.

Synthesis, Structure and Luminescent Properties of Rare‐Earth‐Metal Oxyacridinates

“…The complexes with Acr Me ligands (Sc (3), La (6), Sm (8), Gd (10) and Yb (12)) are compounds of red-burgundy color and with AcrBr ligands -red-violet color (Sc (4), La (7), Sm (9), Gd (11) and Yb (13)). All compounds are readily soluble in common organic solvents, stable in air in the solid state, while in the solution they decompose within a few minutes.…”

“…The assumption is confirmed by the properties of boron hydroxyacridine complexes which showed good photochemical stability and bright solid-state fluorescence. [11] However the luminescence activity of Mg, [5] Zn, [12] Co, Ni, Cu [13] and Pd [14] complexes was low and caused mainly by ancillary ligands in heteroligand systems. The oxyacridine complexes of Al, Ga and In were also obtained to compare the chelating ability, the steric and electronic properties of 8-hydroxyquinoline and HAcr derivatives.…”

CdS QDs-Decorated Self-Doped γ-Bi2MoO6: A Sustainable and Versatile Photocatalyst toward Photoreduction of Cr(VI) and Degradation of Phenol

“…From this analysis, the Stokes shift is calculated to be 84 nm (Figure S1), which indicates the weak self-absorption and low energy loss of the composites. 22 Because the broad symmetric emission peaks are not at constant wavelength when excited with various excitation wavelengths, it can be suggested that the CBBMO composites are not with a monodisperse set of CdS QDs.…”

The Design Strategy for an Aggregation- and Crystallization-Induced Emission-Active Molecule Based on the Introduction of Skeletal Distortion by Boron Complexation with a Tridentate Ligand

“…Herein, we report opposite changes in emission efficiencies between the solution and solid of the modified azomethine-boron complexes BPhQ and BPhQm with or without skeletal distortion around the boron complexation moiety, respectively. In general, quinoline-based boron complexes have been considered to be a class of highly efficient luminescent dyes in solution owing to their rigid and planar structures [41][42][43][44]. Indeed, BPhQm possesses a planar structure, while BPhQ intrinsically involves distortion, although electronic conjugation can be developed through both molecules.…”