Feeling blue: the luminescence of a triarylboron compound has a high quantum yield (at least 0.64) over a wide temperature range (-50 to +100 °C) and changes from green to blue as the temperature is increased. The luminescence color was determined by the population of the two distinct excited-state conformations-a local excited state (high temperature) and a twisted intramolecular charge-transfer state (low temperature).

The color purple: A siloxy‐functionalized benzamide (see picture) is a highly efficient fluoride ion sensor in water. The sensor, which is activated when the OSi bond is cleaved by fluoride ions, provides two independent modes for signal recognition. In colorimetric mode, the fluoride ion concentration is transformed into a fluorescence signal that can be observed directly with the naked eye.

A novel class of 2-(2'-hydroxyphenyl)benzothiazole-based (HBT-based) excited-state intramolecular proton-transfer (ESIPT) compounds, N,N'-di[3-Hydroxy-4-(2'-benzothiazole)phenyl]isophthalic amide (DHIA) and N,N'-di[3-Hydroxy-4-(2'-benzothiazole)phenyl]5-tert-butyl-isophthalic amide (DHBIA) has been feasibly synthesized and the properties of their nanoparticles in THF/H2O mixed solvent were investigated. Both compounds were found to exhibit aggregation-induced emission enhancement (AIEE) due to restricted intramolecular motion and easier intramolecular proton transfer in solid state. On identical experimental conditions, the emission of DHBIA aggregates increased more remarkably than that of DHIA. Different aggregation forms of these two organic compounds, due to the steric hindrance of a single tert-butyl group, could be responsible for the notably different degrees of the fluorescence enhancement. Their aggregation modes were investigated on the basis of time-dependent absorption, scanning electron microscope (SEM) images, and molecular modeling with theoretical calculation. The photophysical dynamics were also depicted based on the extremely fast ESIPT four-level cycle.

Singlet fission and triplet-triplet annihilation represent two highly promising ways of increasing the efficiency of photovoltaic devices. Both processes are believed to be mediated by a biexcitonic triplet-pair state, 1 (TT). Recently however, controversy has arisen over the role of 1 (TT) in triplet-triplet annihilation.Here we use intensity-dependent, low-temperature photoluminescence measurements, combined with kinetic modelling, to show that distinct 1 (TT) emission arises directly from triplet-triplet annihilation in high-quality pentacene single crystals and anthradithiophene (diF-TES-ADT) thin films. This work demonstrates that a real, emissive triplet-pair state acts as an intermediate in both singlet fission and triplet-triplet annihilation and that this is true for both endo-and exo-thermic singlet fission materials.

LB films of three amphiphilic tris(phthalocyaninato) rare earth triple-decker complexes with crown-ethers as hydrophilic heads and long alkyl chains as hydrophobic tails have been prepared and found to display very well ordered layer structures, as proved by pi-A isotherms, UV-vis and polarized absorption spectra, X-ray diffraction experiments, and microscopic morphology characterization. These LB films have been fabricated into field-effect transistor (FET) devices, which show carrier mobilities as high as 0.24-0.60 cm2 V-1 s-1, among the highest mobilities achieved thus far for all LB film-based OFETs.

Triplet–triplet annihilation upconversion (TTA-UC) has great potential to significantly improve the light harvesting capabilities of photovoltaic cells and is also sought after for biomedical applications. Many factors combine to influence the overall efficiency of TTA-UC, the most fundamental of which is the spin statistical factor, η, that gives the probability that a bright singlet state is formed from a pair of annihilating triplet states. The value of η is also critical in determining the contribution of TTA to the overall efficiency of organic light-emitting diodes. Using solid rubrene as a model system, we reiterate why experimentally measured magnetic field effects prove that annihilating triplets first form weakly exchange-coupled triplet-pair states. This is contrary to conventional discussions of TTA-UC that implicitly assume strong exchange coupling, and we show that it has profound implications for the spin statistical factor η. For example, variations in intermolecular orientation tune η from to through spin mixing of the triplet-pair wave functions. Because the fate of spin-1 triplet-pair states is particularly crucial in determining η, we investigate it in rubrene using pump–push–probe spectroscopy and find additional evidence for the recently reported high-level reverse intersystem crossing channel. We incorporate all of these factors into an updated model framework with which to understand the spin statistics of TTA-UC and use it to rationalize the differences in reported values of η among different common annihilator systems. We suggest that harnessing high-level reverse intersystem crossing channels in new annihilator molecules may be a highly promising strategy to exceed any spin statistical limit.

A triple fluorescent compound, N-salicylidene-3-hydroxy-4-(benzo[d]thiazol-2-yl)phenylamine (SalHBP), was dispersed in solid polymers and was developed as a white-light-emitting source in LED by using it as the first simple single compound with different configurations. The CIE coordinates were at (0.29, 0.35), close to those of pure white light. To explore speciation mechanisms in this single compound white light, SalHBP was dissolved in protic, nonpolar, and moderate polar solvent, respectively. Upon excitation, blue, green, and yellowish green emissions were observed from the three solutions at various temperatures. The conformation of SalHBP at room temperature was described by a Car-Parrinello molecular dynamics simulation. With the aid of hybrid density functional theory at the B3LYP/TZVP and PBE0/TZVP levels, three observed emission bands of SalHBP were assigned from the five most probable excited state conformations that were derived from four ground state conformations. The effect of solvent on the emission of SalHBP was summarized as a possibility for forming intermolecular hydrogen bonds between solvent and SalHBP molecules and competition between intra- and intermolecular hydrogen bonds.

A novel perylene diimide (PDI) derivative with typical amphiphilic character, 2, was designed and prepared. The spectroscopic studies on this compound in solution revealed the face-to-face dimeric configuration and effective pi-pi interaction between the two perylene rings. This amphiphilic PDI derivative was fabricated into highly ordered films by Langmuir-Blodgett (LB) technique and fabricated into an organic field effect transistor (OFET), which shows carrier mobility around 0.05 cm(2) V(-1) s(-1) and current modulation of 10(3). This OFET performance is much better than that of monomeric PDI 1 and can be attributed to the unique face-to-face structure of 2, which promotes the interactions between neighboring PDI ring in LB film as indicated by the pi-A isotherms and UV-vis absorption.