In this paper, we present an integrating sphere instrument for absolute luminescence quantum yield measurements from the visible to near-infrared (NIR) spectral region (λ = 350–1650 nm). The integrating sphere is equipped with a Xe light source and two spectrally corrected multichannel analyzers using a back-thinned charge-coupled device (CCD) and InGaAs detector, one for measurements in the visible to NIR wavelength region (λ = 350–1100 nm) and the other for the NIR wavelength region (λ = 900–1650 nm). The combination of the two optical multichannel analyzers allows measurement of the absolute quantum yield of NIR emissions with good sensitivity. Using this new instrument and platinum(II) meso-tetra(pentafluorophenyl)porphine (PtTFPP) as a sensitizer, we performed the first absolute measurements of quantum yield (Φp1Δ) of the a1Δg (v′ = 0) → X3Σg– (v″ = 0) emission at 1270 nm from molecular oxygen in different solvents. The quantum yields Φp1Δ in CCl4 and CS2 under infinite dilution of sensitizer were determined to be 2.2 × 10–2 and 6.4 × 10–2, respectively. Using the Φp1Δ value in CCl4, the quantum yields in other solvents were determined based on the relative method. From the phosphorescence quantum yields and the lifetimes of O2(a1Δg) taken under identical experimental conditions, we evaluated the radiative and nonradiative rate constants of O2(a1Δg), which are key parameters to understand the photophysical properties of singlet oxygen in solution. The quantum yields and radiative and nonradiative rate constants obtained in the present study were compared with the literature values determined based on the relative method.
π-Extended thiadiazoles 4-8 fused with various electron-donating heteroaromatic moieties have been designed and synthesized. Just like thiadiazoles 1-3 synthesized previously, 4-8 exhibit intramolecular charge-transfer (CT) interactions, moderate-to-good fluorescence quantum yields of up to 0.78, and electrochemical amphoterism. In comparison with 1-3, the benzannulation in thiadiazoles 4-7 moderately extends the π conjugation and significantly increases the stability of the cationic species formed upon electrochemical oxidation. The fluorescence quantum yields increase remarkably from 3 to 6 and 7 due to the efficient suppression of nonradiative intersystem crossing resulting from the benzannulation. The properties of 4-8 strongly reflect the different species annulated to the pyrrole rings, namely benzothiophene, naphthalene, and benzofuran. Eleven crystals, including poly- and pseudopolymorphic crystals of 1 (1-Crys.(Y) and 1-Crys.(G)), 2 (2-Crys.(O) and 2-Crys.(G)), 4 (4-Crys.(O) and 4-Crys.(G)), and 6 (6-Crys.(O) and 6-Crys.(G)), were obtained and characterized by X-ray crystallography. The fluorescence colors and efficiencies are distinct for each poly- and pseudopolymorph of 1, 2, 4, and 6. It has been suggested that both the extent of the electronic interactions in the π-stacked dimers and the presence of excitonic interactions originating in the 1D face-to-face slipped columns affect the fluorescence wavelengths of the poly- and pseudopolymorphs.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
In this study, we report a preparation and an aggregate emission behavior of an amphiphilic donor-acceptor dye, which is composed of a triphenylamine-benzothiadiazole donor-acceptor chromophore and two water-soluble hexa(ethylene glycol) chains. The dye is strongly fluorescent in nonpolar solutions such as cyclohexane and toluene, whereas the emission intensity is reduced in aprotic polar solutions such as DMF and acetonitrile. This fluorescence reduction correlates with the increase in polarity, by which the transition from a local excited state to a highly polarized excited state is facilitated, leading to an increased nonradiative deactivation rate. Furthermore, significant fluorescence quenching is observed in protic polar solutions such as ethanol and methanol. Hydrogen-bonding interactions between the dye and the protic solvent molecules further accelerate the deactivation rate. In contrast, in a water solution, red light emission is achieved distinctly at 622 nm with a relatively large fluorescence quantum yield of 0.20. This red emission is related to the aggregation of the dye molecules grown in water. The kinetic analysis from the fluorescence rate constant and nonradiative rate constant indicates that the nonradiative deactivation channel is restricted in water. The formed aggregate, which was indicated by transmittance electron microscopy as a spherical aggregate morphology with a diameter of 3-4 nm, provides a less polar hydrophobic space inside the aggregate structure, by which hydrogen-bonding and the subsequent quenching are restricted, leading to the reduction of the nonradiative deactivation rate.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
