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We report a series of molecules that spontaneously self-organize into small electroluminescent domains of sub-micrometer dimensions when dissolved in tetrahydrofuran. The self-assembled spherical aggregates have an average diameter of 300 nm and exhibit efficient energy transfer from the blue to the green or red component. The aggregates can be chromatically addressed or patterned by selective bleaching of the energy-acceptor component using a laser source. This allows the fabrication of electroluminescence devices by directly photopatterning the active layer without the need of additional steps. Submicron features (700 nm) can be achieved using a collimated light source.

UV light-emitting electrochemical cells (LECs) were, for the first time, achieved by the ionic 2,2′-bifluorene derivative, 1, which was synthesized through covalent tethering of methylimidazolium moieties as pendent groups. LEC devices incorporating ionic bifluorene 1 without (Device I) and with (Device III) the presence of poly(methyl methacrylate) (PMMA) exhibited UV EL emissions centered at 388 and 386 nm with maximum external quantum efficiencies and power efficiencies of 1.06% and 7.44 mW W−1 for Device III and 0.15% and 1.06 mW W−1 for Device I, respectively. Transmission electron microscopy (TEM) images showed that 1 tends to form nanospheres due to amphiphilic nature. The presence of PMMA unified the size of nanospheres which greatly reduced the void area in films, suppressing the current leakage and enhancing the device efficiency. Furthermore, thicker thickness of the emissive layer of LECs increases the distance between carrier recombination zone and electrodes to avoid exciton quenching. Thus, a sevenfold increase in device efficiency was obtained in thicker UV LECs containing PMMA (Device III) as compared to thinner UV LECs based on neat films of 1 (Device I). The EL emissions in the UV region are successfully achieved by LECs based on 1, which are so far the shortest emission wavelength achieved in LECs.

Non-precious metal catalysts of the oxygen reduction reaction are highly favored for use in polymer electrolyte fuel cells (PEFC) because of their relatively low cost. Here, a new carbon-black-supported pyrolyzed Co-corrole (py-Co-corrole/C) catalyst of the oxygen reduction reaction (ORR) in a PEFC cathode is demonstrated to have high catalytic performance. The py-Co-corrole/C at 700 °C exhibits optimized ORR activity and participates in a direct four-electron reduction pathway for the reduction of O2 to H2O. The H2-O2 PEFC test of py-Co-corrole/C in the cathode reveals a maximum power density of 275 mW cm−2, which yields a higher performance and a lower Co loading than previous studies of Co-based catalysts for PEFCs. The enhancement of the ORR activity of py-Co-corrole/C is attributable to the four-coordinated Co-corrole structure and the oxidation state of the central cobalt.

A high performance continuous-wave cavity ringdown spectrometer using a rapidly swept cavity has been applied to investigate weak absorption of CO2 line near 1064 nm. In the experimental setup, offset locking of the Nd:YAG laser to other iodine-stabilized Nd:YAG laser provides a frequency accuracy better than 20 kHz. The ringdown time was obtained by fitting the experimental ringdown data to a theoretically obtained ringdown curve. The absorption coefficient and absolute center wavelength are determined with accuracy better than two orders of magnitude with respect to the previous observations. Our experimental setup yields high performance in a relatively simple, low cost, and compact system that is amenable to chemical analysis of trace gases in medicine, agriculture, industry, and the environment.

A new porphyrin appended with four crown ether units at meso-positions via an acetylene bridge was synthesized and structurally characterized, and its complexation with a variety of metal and diammonium cations was investigated.

A series of novel star-shaped porphyrin-triarylamine conjugates were synthesized by palladium-catalyzed cross-coupling reactions. The spectroscopic and electrochemical studies show that pi-conjugation of the porphyrin core is extended to the triarylamine moieties.

Sonogashira coupling of zinc 5,10,15,20-tetraethynylporphyrin with various phenyl iodides under mild conditions afforded good yields of the corresponding zinc porphyrins. This method is applicable to a variety of aryl iodides including meso-substituted iodoporphyrin to form a conjugated star-shaped multiporphyrin. The UV-Vis spectra show that peak broadening, red shifts, and changes in the oscillator strength of absorptions increase with the extension of pi-conjugation. In the electrochemical measurements, the first oxidation of porphyrins 4-9 occurs at potentials in the range +0.89 to +1.08 V, which are comparable to that of ZnTPP (TPP = tetraphenylporphyrin). The first reduction was observed at potentials from -0.73 to -0.89 V, which is anodically shifted by 390-550 mV as compared to that of ZnTPP, and the second reduction occurs at potentials in the range -1.12 to -1.33 V. The para-substituted tetrakis(phenylethynyl)porphyrins show substituent effects on their redox chemistry and exhibit only slight substituent effects in their emission and absorption maxima.

Thermally activated delayed fluorescence (TADF) properties of a dicarbazole-triazine compound, 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9'-phenyl-3,3'-bicarbazole (CzT), and its OLED characteristics were investigated. An estimated small energy gap of about 90 meV between the singlet and triplet energy states of CzT made the up-conversion of triplet excitons back to a singlet state possible. The origin of the observed delayed fluorescence has been shown to be thermally activated delayed fluorescence. An organic light emitting diode (OLED) with CzT as an emitter showed the maximum external quantum efficiency (EQE) of 6%. For comparison, another carbazole-triazine derivative of 3-(2'-(4,6-diphenyl-1,3,5-triazin-2-yl)-[1,1'-biphenyl]-2-yl)-9-phenyl-9H-carbazole (PhCzTAZ) with a similar structure was also studied. PhCzTAZ showed a low fluorescence quantum yield with no TADF.

A porphyrin derivative possessing orthogonal self-assembly units displays in situ reversible transformation of aggregate morphology between nano-rods and hollow spheres upon exposure to different solvents.

A novel bipolar host material 9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9′-phenyl-3,3′-bicarbazole (CzT) comprising a dicarbazole donor linking to an electron deficient 1,3,5-triazine acceptor was synthesized and characterized. The molecular design of CzT allows the spatial separation of HOMO and LUMO on the donor and acceptor moieties, respectively, giving sufficient triplet energy (2.67 eV) together with promising physical properties and morphological stability (Tg = 134 °C). This tailor-made material was used as a host for an efficient yellowish-green iridium complex, bis(o-tolylpyrimidinato-N,C2′)Ir(III)acetylacetonate [(TPm)2Ir(acac)]; the as-fabricated phosphorescent OLEDs (PHOLEDs) demonstrated high performance, with maximum efficiencies of 20.0% (75.7 cd A−1 and 71.3 lm W−1) and 20.1% (76.3 cd A−1 and 72.7 lm W−1) achieved in trilayer and bilayer device architectures, respectively. The efficiency of the trilayer device can sustain ∼20% over a wide brightness range from 102 to 103cd m−2 due to the more effective confinement of emissive excitons within the emitting layer.

Two anionic iridium complexes Na[Ir(2-(p-tolyl)pyridine)2(CN)2] (A1) and Na[Ir(2-phenylquinoline)2(CN)2] (A2) were synthesized and characterized for use in light-emitting electrochemical cells (LECs). The photophysical and electrochemical studies show that the emission wavelengths and the LUMO energy levels of these complexes are governed by the conjugation length of the cyclometalated ligands. Single-layer LEC devices incorporating anionic complexes were fabricated and tested. Suffering from poor solubility of the anionic complexes, the device performances were rather limited due to the lack of film uniformity. The solubility issue was circumvented by using 18-crown-6 as an additive, efficiently eliminating the cluster structure formed by ion-dipole (sodium ion–lone pair of the nitrile ligand) interaction. The maximum brightness and peak external quantum efficiency achieved by crown-mediated LEC were up to 69 cd m−2 and 1.38%, respectively. The device efficiencies exhibit a great dependence with the LUMO level of the complex, suggesting substantial importance of the electron injection process.

A series of meso-to-meso ethynyl-bridged multiporphyrin arrays have been synthesized using Sonogoshira palladium-catalyzed cross-coupling reactions involving the appropriate ethynylporphyrin and iodoporphyrin precursors. The absorption spectra of these multiporphyrins show splitting of the Soret bands and significant red shifts of the Q bands as compared to the combination of the corresponding components. These conjugated multiporphyrins also show red shifts in their emission spectra as the pi-conjugation is expanded. In the electrochemical measurements, the porphyrins dimer 7 shows two 1 - e- oxidations at E(1/2) = +0.63 and +0.76 V for the first electron abstraction from the two porphyrin rings, indicating electronic communication between the two porphyrin units. The porphyrin trimer 4 exhibits the first and second 1 - e- oxidations at E(1/2) = +0.68 and +0.77 V, respectively, which correspond to the two outer porphyrins. The cyclic voltammogram of pentamer 5 shows two overlapping 1 - e- couples at E(1/2) = +0.56 and +0.66 V, and one 2 - e- couple at E(1/2) = +0.86 V, for the four outer porphyrin units. These results demonstrate that in the porphyrin trimer and pentamer the individual peripheral porphyrin units are electrochemically coupled via a central porphyrin core. The UV-Vis-NIR spectra of the oxidized species of these multiporphyrins exhibit a broad intervalence charge transfer (IVCT) band in the region from 1200 to 3000 nm. The present work shows that a central porphyrin unit appended with ethynyl bridges affords strong electronic interactions between the peripheral porphyrin rings over a distance of about 15 A.

Hexafluorobut-2-yne reacts with Ir(NO)(PPh3)3 to form a complex whose identity was established by X-ray crystallography as di-µ-hexafluorobut-2-enylene-bis-[cis-triphenylphosphinenitrosyliridium(I)]; tetrafluoroethylene reacts to form Ir(NO)(C2F4)(PPh3)3 which readily loses one molecule of PPh3.

In contrast with lumiflavin or 7,8,10-trimethyl-isoalloxazine bis(naphthalene-2,3-diol), the 1 : 2 complex of 10-propylisoalloxazine with naphthalene-2,3-diol is orange and contains one flavin–naphthalenediol pair separated by 3·35 A, suggesting a possible charge-transfer interaction.