Development of Strong Visible-Light-Absorbing Cyclometalated Iridium(III) Complexes for Robust and Efficient Light-Driven Hydrogen Production.

Weak light absorption of common Ir(III) complexes (e. g., using phenylpyridine as the ligand) has hindered their applications in photocatalytic hydrogen generation from water as an efficient photosensitizer. To address this issue, a series of cyclometalated Ir(III) complexes (Ir1-Ir5), featuring different electron-donating substituents to enhance the absorptivity, have been synthesized and studied as photosensitizers (PSs) for light-driven hydrogen production from water. Ir6-Ir7 were prepared as fundamental systems for comparisons. Electron donors, including 9-phenylcarbazole, triphenylamine, 4,4'-dimethoxytriphenylamine, 4,4'-di(N-hexylcarbazole)triphenylamine moieties were introduced on 6-(thiophen-2-yl)phenanthridine-based cyclometalating (C^N) ligands to explore the donor effect on the hydrogen evolution performance of these cationic Ir(III) complexes. Remarkably, Ir4 with 4,4'-dimethoxytriphenylamine achieved the highest turn-over number (TON) of 12 300 and initial turnover frequency (TOFi ) of 394 h-1 , with initial activity (activityi ) of 547 000 µmol g-1 h-1 and initial apparent quantum yield (AQYi ) of 9.59 %, under the illumination of blue light-emitting diodes (LEDs) for 105 hours, which demonstrated a stable three-component photocatalytic system with high efficiency. The TON (based on n(H2 )/n(PSr)) in this study is the highest value reported to date among the similar photocatalytic systems using Ir(III) complexes with Pt nanoparticles as catalyst. The great potential of using triphenylamine-based Ir(III) PSs in boosting photocatalytic performance has also been shown.

Nanoimprint Lithography-Directed Self-Assembly of Bimetallic Iron-M (M=Palladium, Platinum) Complexes for Magnetic Patterning.

Self-assembly of d8 metal polypyridine systems is a well-established approach for the creation of 1D organometallic assemblies but there are still challenges for the large-scale construction of nanostructured patterns from these building blocks. We describe herein the use of high-throughput nanoimprint lithography (NIL) to direct the self-assembly of the bimetallic complexes [4'-ferrocenyl-(2,2':6',2''-terpyridine)M(OAc)]+ (OAc)- (M=Pd or Pt; OAc=acetate). Uniform nanorods are fabricated from the molecular self-organization and evidenced by morphological characterization. More importantly, when top-down NIL is coupled with the bottom-up self-assembly of the organometallic building blocks, regular arrays of nanorods can be accessed and the patterns can be controlled by changing the lithographic stamp, where the mold imposes a confinement effect on the nanorod growth. In addition, patterns consisting of the products formed after pyrolysis are studied. The resulting arrays of ferromagnetic FeM alloy nanorods suggest promising potential for the scalable production of ordered magnetic arrays and fabrication of magnetic bit-patterned media.

Panchromatic Sensitization with ZnII Porphyrin-Based Photosensitizers for Light-Driven Hydrogen Production.

Three molecular photosensitizers (PSs) with carboxylic acid anchors for attachment to platinized titanium dioxide nanoparticles were studied for light-driven hydrogen production from a fully aqueous medium with ascorbic acid (AA) as the sacrificial electron donor. Two zinc(II) porphyrin (ZnP)-based PSs were used to examine the effect of panchromatic sensitization on the photocatalytic H2 generation. A dyad molecular design was used to construct a difluoro boron-dipyrromethene (bodipy)-conjugated ZnP PS (ZnP-dyad), whereas the other one featured an electron-donating diarylamino moiety (YD2-o-C8). To probe the use of the ZnP scaffold in this particular energy conversion process, an organic PS without the ZnP moiety (Bodipy-dye) was also synthesized for comparison. Ultrafast transient absorption spectroscopy was adopted to map out the energy transfer processes occurring in the dyad and to establish the bodipy-based antenna effect. In particular, the systems with YD2-o-C8 and ZnP-dyad achieved a remarkable initial activity for the production of H2 with an initial turnover frequency (TOFi ) higher than 300 h-1 under white light irradiation. The use of ZnP PSs in dye-sensitized photocatalysis for the H2 evolution reaction in this study indicated the importance of the panchromatic sensitization capability for the development of light absorbing PSs.

Starburst Triarylamine Donor-Based Metal-Free Photosensitizers for Photocatalytic Hydrogen Production from Water.

Three metal-free molecular photosensitizers (S1-S3) featuring a starburst triarylamine donor moiety have been synthesized. They show attractive photocatalytic performance in visible light-driven H2 production from water in their platinized TiO2 composites. A remarkable H2 turnover number (TON) of 10 200 (48 h) was achieved in an S1-anchored system.

Patterning of L10 FePt nanoparticles with ultra-high coercivity for bit-patterned media.

L10-ordered FePt nanoparticles (NPs) with ultra-high coercivity were directly prepared from a new metallopolyyne using a one-step pyrolysis method. The chemical ordering, morphology and magnetic properties of the as-synthesized FePt NPs have been studied. Magnetic measurements show the coercivity of these FePt NPs is as high as 3.6 T. Comparison of NPs synthesized under the Ar and Ar/H2 atmospheres shows that the presence of H2 in the annealing environment influences the nucleation and promotes the growth of L10-FePt NPs. Application of this metallopolymer for bit-patterned media was also demonstrated using nanoimprint lithography.

Synthesis and Characterization of Phenothiazine-Based Platinum(II)-Acetylide Photosensitizers for Efficient Dye-Sensitized Solar Cells.

Three new unsymmetrical phenothiazine-based platinum(II) bis(acetylide) complexes PT1-PT3 with different electron-donating arylacetylide ligands were synthesized and characterized. Their photophysical, electrochemical, and photovoltaic properties have been fully investigated and the density functional theory (DFT) calculations have been carried out. Under AM 1.5 irradiation (100 mW cm(-2)), the PT1-based dye-sensitized solar cell (DSSC) device exhibited an attractive power conversion efficiency (η) up to 5.78 %, with a short-circuit photocurrent density (J(sc)) of 10.98 mA cm(-2), an open-circuit photovoltage (V(oc)) of 0.738 V, and a fill factor (ff) of 0.713. These findings provide strong evidence that platinum-acetylide complexes have great potential as promising photosensitizers in DSSC applications.