Yih Hsing Lo

Platinum(II) cyclometallates featuring broad emission bands and their applications in color-tunable OLEDs and high color-rendering WOLEDs

Two phosphorescent platinum(II) cyclometallated complexes with phenoxy groups (1 and 2) have been developed. The modified organic ligands derived by combining the phenoxy moiety and 2-phenylpyridine conferred them with a more flexible structure, leading to superior intermolecular interaction properties of the resulting Pt(II) metallophosphors. Because of the excimer formation induced by Pt(II) complexes 1 and 2, the emission color can be tuned over a wide range from cyan to orange by simply increasing the concentration of the Pt(II) metallophosphors. Inspired by their broad emission band, color tunability and outstanding electroluminescence (EL) performance, these two Pt(II) phosphors complemented with blue fluorescent emitter 4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl (BCzVBi) were employed in manufacturing high color-rendering white organic light-emitting devices (WOLEDs). In such simple two-emitter systems, 1-based WOLEDs exhibited reasonable EL performance with an external quantum efficiency (ηext) of 11.7%, luminance efficiency (ηL) of 29.1 cd A−1, power efficiency (ηp) of 16.9 lm W−1 and color rendering index (CRI) of 77, whereas 2-based WOLEDs demonstrated an ηext of 10%, ηL of 21.7 cd A−1, ηp of 10.7 lm W−1 and CRI of 88.

Porphyrin-based metallopolymers: synthesis, characterization and pyrolytic study for the generation of magnetic metal nanoparticles

Metallopolymers with different metal centers, pendant groups and linkages exhibit diverse structures and properties, thus giving rise to versatile applications, e.g., as emissive and photovoltaic materials, optical limiters, materials for nano-electronics, information storage, nanopatterning and sensing, macromolecular catalysts and artificial enzymes, and stimuli-responsive materials. Recently, metallopolymers as precursors to generate monometallic or metal alloy nanoparticles are of great interest owing to their advantages of ease of processability, atomic level mixing, and stoichiometric control over composition. By taking advantage of the template effect of porphyrin compounds, a series of monometallic and heterobimetallic polymers are synthesized which are characterized by NMR, IR, HRMS, EA, GPC and TGA, respectively. Photophysical properties of these metallopolymers are also studied by UV-vis spectroscopy. Pyrolytic treatment of these metallopolymers generates various magnetic monometallic and metal alloy nanoparticles which can be used in data storage, catalysis, biomedicine, etc.

Molecular engineering of starburst triarylamine donor with selenophene containing π-linker for dye-sensitized solar cells

A series of new D–π–A organic photosensitizers 7a–7d featuring a novel starburst electron donor unit and uncommon selenophene containing π-linker were synthesized, characterized, and applied for fabrication of dye-sensitized solar cells (DSSCs). Dyes 11d–13d with thiophene or phenyl ring as the π-linker also were synthesized for comparison. The best power conversion efficiency (PCE) of 6.67% was attained for 11d with a relatively high open-circuit voltage (Voc) of 0.825 V using conventional I−/I3− redox electrolyte in DSSCs, and this value reaches about 84% of the device based on standard dye N719 (7.91%) under the same device fabrication conditions. Electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) were applied to verify the findings. All the results suggest that starburst electron donor design strategy can be used to minimize dye aggregation on TiO2 and to slow down the charge recombination kinetics in DSSCs to improve the photovoltaic performance. Effects of using selenophene as the π-linker building block on the photovoltaic parameters also were explored and evaluated.

Synthesis, characterization and photovoltaic properties of benzo[1,2-b:4,5-b′]dithiophene-bridged molecules

Four new acceptor–donor–acceptor based organic small molecules with the benzo[1,2-b:4,5-b′]dithiophene (BDT) unit as the central donor group, benzothiadiazole (BT) or fluoro-substituted benzothiadiazole as the acceptor, and different end-capping groups (BTBDT1–BTBDT4) have been synthesized and tested for solution-processed bulk-heterojunction organic solar cells. The absorption spectra, electronic energy levels, hole mobilities and solar cell performance of these compounds were investigated. All compounds show broad absorption in the visible range. The PCE of the solar cell device based on BTBDT3/PC71BM (1:2, w/w) reached 3.91% with a Jsc of 10.08 mA cm−2, a Voc of 0.90 V and a FF of 0.43, under illumination of AM 1.5G, 100 mW cm−2.

Synthesis, Structures and Properties of Novel Platinum(II) Acetylide Complexes and Polymers with Tri(tolyl)phosphine as the Auxiliary Ligand

A new family of luminescent platinum(II) acetylide complexes and polymers were formed by the copper(I) catalyzed reaction of cis-[PtCl2(PR3)2] (R=C6H5–p-CH3) with appropriate acetylide ligands. The reaction of metal precursors with 2.5 equivalents of monoterminal acetylide ligands provided metal complexes trans-[Pt(p-tolyl3P)2(C≡C-R)2] (R=C6H4-p-NO2 (1) C6H4 -p-CH3 (2)), and equimolar amounts of diterminal ligand and metal chloride precursor, under reflux, afforded the metal poly-yne polymers [-Pt(p-tolyl3P)2C≡C–R–C≡C–]n, (R=biphenyl and 2,5-dioctyloxybenzene). Characterization of the newly developed polymer and metal complexes was accomplished by FT-IR, multinuclear NMR (1H, 31P, 13C) and mass spectrometry, as well as elemental analysis. The molecular structure of the metal complex trans-[Pt(p-tolyl3P)2(C≡CC6H4–p-NO2)2] (1) was confirmed by single crystal X-ray crystallography. The electronic absorption and photoluminescence spectra of the metal complexes and polymers have been used to probe their photophysical properties. The studies reveal that the presence of heavy metal atom and substituent groups on the phenyl ring of the ligands can enhance the efficiency of intersystem crossing from the S1 singlet excited state to the T1 triplet excited state and thus give intense phosphorescence.

One-pot synthesis of cubic ZnSe entangled nanowires and hexagonal Se nanorods

Se nanorods, ZnSe nanowires and their mixture can be prepared by a single process at different reaction temperatures between 300 to 360 °C. The Se nanorods are generally longer than 1 μm, while the ZnSe nanowires have an entangled structure and have a diameter and length of 15–20 nm and 0.3–2 μm, respectively.

Synthesis, characterization and electrochemistry of some metal carbonyl clusters derived from ferrocenylethynylpyridine

The chemical reactivity of ferrocenylethynylpyridine ligand with some metal complexes has been studied. Ligation of this ferrocenyl-functionalized pyridyl metalloligand with triosmium carbonyl cluster [Os3(CO)10(NCMe)2] via oxidative addition led to a new supramolecular heterobimetallic cluster [Os3(CO)10(μ-H){μ-NC5H3C≡C(η5-C5H4)Fe(η5-C5H5)}] 1 in good yield. Coordination of Co2(CO)8 with the alkyne functionality of 1 gave another new heterotrimetallic cluster complex [Os3(CO)10(μ-H){μ-NC5H3{C2Co2(CO)6}(η5-C5H4)Fe(η5-C5H5)}] 2 in which the molecule possesses a Co2C2 core adopting the pseudo-tetrahedral geometry having the alkyne bond lying perpendicular to the Co–Co vector. Characterization of 1 and 2 by IR and 1H NMR spectroscopies indicated that these complexes consist of an orthometalated trinuclear carbonyl cluster unit rigidly connected to a ferrocenyl unit. Electrochemical studies on 1 and 2 revealed that both of them undergo a reversible one-electron oxidation at iron followed by an irreversible oxidation of the Os3 cluster core. Another simple mononuclear zinc(II) complex [ZnCl2{(NC5H4C≡C(η5-C5H4)Fe(η5-C5H5)}2] 3 was also prepared for comparison of the electrochemical data with those of 1 and 2.

Antifungal study of substituted 4-pyridylmethylene-4′-aniline Schiff bases

Otomycosis is a superficial infection of the ear caused by fungi. The disease may occur in the pinna, external auditory canal and tympanic membrane of humans and animals. Aspergillus niger and Candida albicans are the most prevalent fungal species responsible for otomycosis. In our study, the potential antifungal properties of a series of Schiff bases was examined. The synthesized compounds (1–14) were investigated for their minimum inhibitory concentration, minimum fungicidal concentration and zone of clearance against Aspergillus niger and Candida albicans. Compounds 5 and 6 with alkyl chain containing 6 or 7 carbon atoms exhibited an obvious fungicidal activity with the MIC/MFC ratio of 2. Zone of clearance study also demonstrated that both compounds 5 and 6 produced noticeable clear zones against the tested fungi as compared to fluconazole. The time-kill kinetic study showed that Candida albicans colonies were reduced by more than 3 logs after 24 h exposure to compound 5 at 4 and 8 × MIC levels. Both compounds 5 and 6 at a concentration of 50 μg mL−1 exhibited satisfactory cell viability towards human skin keratinocytes. Our results suggest that these compounds may be considered as potential drug candidates for the treatment of Aspergillus niger and Candida albicans ear infections.