Chiral Triarylborane-based Small Organic Molecules for Circularly Polarized Luminescence

Circularly polarized luminescence (CPL) has shown promising application potentials in 3D display, optical data storage, smart sensors/probers, CPL lasers, and light source for asymmetric photosynthesis. In the last decade, the CPL-active small organic molecules (CPL-SOMs) have attracted rapidly increasing research interest owing to the great advantages of SOMs, such as high luminescence efficiency, facile modification of chemical structure, fine emission wavelength tuning, precise relationships between structure and properties, and as well as easy fabrication. Promoted by the unique effects of boryl group, such as strong electron-accepting ability, great steric effect, and Lewis acidity to bind with Lewis bases, we herein summarized our recent research results about the creation of CPL-SOMs by modification of chiral scaffolds, such as [2.2]paracyclophane, [5]/[7]helicene, and binaphthyl, with boryl group. The preliminary results have well demonstrated that the chiral triarylborane-based SOMs exhibit promising CPL properties, such as intense CPL in combination of high luminescence dissymmetry factor (|g_lum |) with high fluorescence efficiency, solvent-induced sign inversion, facile emission wavelength tuning, high fluorescence efficiency in the solid, and substituent-induced sign inversion.

Ratiometric dual fluorescence tridurylboron thermometers with tunable measurement ranges and colors

Noncontact ratiometric fluorescent thermometers have received great interests in recent years. Besides being a sensitive and easily observable detection signal, the ratiometric dual fluorescence are also highly accurate and resistable to interference. However, organic molecular thermometers with such fluorescence property are very rare, and their measurement ranges and colors are limited. In this work, a series of ratiometric dual fluorescent tridurylboron thermometers, with tunable measurement ranges and colors, are designed and synthesized. The measurement ranges of the thermometers are -20 °C-40 °C, -10 °C-50 °C and -25 °C-30 °C in solid polymeric systems, and -50 °C-100 °C and -30 °C-110 °C in liquid organic solvent. With decreasing temperature, the fluorescence colors of tridurylboron-MOE thermometers are from green yellow to yellow red, green to green yellow, blue to green. This study provides a novel strategy for developing tunable ratiometric dual fluoresence organic molecular thermometers.

Temperature-sensitive triarylboron compounds based on naphthalene substituents

Since temperature is one of the most important physical parameters, it is of great significance to measure temperature with high space resolution and accuracy. Herein, a series of π-conjugated triarylboron compounds with temperature sensitivity based on naphthalene aromatic groups were designed and synthesized. Their photophysical properties were studied in detail by steady state absorption, emission spectroscopy and time-dependent density functional theory calculation. As the temperature increased, their emission spectra exhibited obvious blue shifts in liquid organic solvent, making ratiometric fluorescence sensing of temperature achievable.

Impact of the 2,2'-Bithienyl Framework on the Charge-Transfer Emission of Triarylborane-Based o,o'-Substituted Biaryls

Two new triarylborane-based o,o'-substituted 2,2'-bithienyls, BT-BNMe ₂ and BT-BNBn ₂ , which contain BMes₂ and NMe₂/NBn₂ groups at the 3,3'-positions, have been synthesized. Similar to the o,o'-substituted biphenyl analogues, BP-BNMe ₂ and BP-BNBn ₂ , which contain BMes₂ and NMe₂/NBn₂ groups at the 2,2'-positions, the steric effect of the amino group has significant influence on the conformation of the 2,2'-bithienyl skeleton. The boryl and amino groups are located at the same side of 2,2'-bithienyls axis with a short B···N distance (3.63 Å) for the NMe₂-substituted BT-BNMe ₂ . On the contrary, the two substituents are arranged on the two different sides of the 2,2'-bithienyls axis for BT-BNBn ₂ , which is modified with bulky NBn₂. Despite the remarkable differences in the steric structure, the two 2,2'-bithienyls display fluorescence at close wavelengths, which is in sharp contrast to the much red-shifted fluorescence of BP-BNMe ₂ than BP-BNBn ₂ . The theoretical calculations demonstrated that the two 2,2'-bithienyls have close highest occupied molecular orbital-lowest unoccupied molecular orbital gaps in the excited state, which firmly support the experimental results. Thus, the parent main chain framework can exhibit great impact on the charge-transfer emission of o,o'-substituted biaryls.

T and V-shaped donor–acceptor–donor molecules involving pyridoquinoxaline: large Stokes shift, environment-sensitive tunable emission and temperature-induced fluorochromism

The critical role of molecular shapes in the environment-sensitive and temperature-induced emission properties of pyridoquinoxaline-based donor–acceptor–donor molecules was demonstrated.