King of the spins is provided by the mixed‐valent Mn19 aggregate as reported by A. K. Powell et al. in their Communication on page 4926 ff. The use of bridging azido ligands leads to a completely ferromagnetically coupled system with a record ground spin state of 83/2. This remarkable molecule has been investigated and characterized by scientists from three laboratories working together in the European Network of Excellence “MAGMANet”, the logo of which provides the background to the cover picture.

Single-walled carbon nanotubes (SWNTs) covalently modified with large porphyrin molecules have been prepared to construct photoelectrochemical devices with nanostructured SnO2 electrodes on which the multiporphyrin-linked SWNTs are deposited electrophoretically. The film of the porphyrin-linked SWNTs on the nanostructured SnO2 electrode exhibited an incident photon-to-photocurrent efficiency as high as 4.9% under an applied potential of 0.08 V vs SCE. The more uniform film and moderate photocurrent generation in the porphyrin-linked SWNT devices can be rationalized by the exfoliation abilities of the bulky porphyrins that yield large steric hindrance around the SWNTs. Direct electron injection from the excited states of the SWNTs to the conduction band of the SnO2 electrode is responsible for the photocurrent generation. Despite the efficient quenching of the porphyrin-excited singlet state by the SWNTs in the porphyrin-linked SWNTs, the photocurrent action spectra revealed that the excitation of the porphyrin moieties makes no contribution to the photocurrent generation. The evolution of an exciplex between the porphyrin-excited singlet state and the SWNTs and the subsequent rapid decay to the ground state without generating the charge-separated state is proposed to explain the unusual photoelectrochemical behavior. The results obtained here will provide valuable information on the design of SWNT-based photoelectrochemical devices.

Novel 5-(5-carboxy-2-thienyl)-10,15,20-tris(2,4,6-trimethylphenyl)-porphyrinatozinc(II) (Zn5S), 5-(5-carboxy-2-furyl)-10,15,20-tris(2,4,6-trimethylphenyl)porphyrinatozinc(II) (Zn5O), and 5-(4-carboxy-2-thienyl)-10,15,20-tris(2,4,6-trimethylphenyl)porphyrinatozinc(II) (Zn4S) were synthesized to evaluate the spacer effects on the structures of the porphyrin films and the photovoltaic properties of the porphyrin-sensitized TiO2 solar cells. Each of the porphyrins showed different adsorption behavior and saturated coverage on the TiO2 surface and photovoltaic properties depending on the identity of heteroatoms in the bridge and the position of carboxylic acid. Specifically, Zn5S-sensitized TiO2 cell displayed larger, maximum incident photon-to-current efficiency of 65% and maximum power conversion efficiency of 3.1% than Zn5O-sensitized TiO2 cell by ∼20% and ∼40%, respectively. We interpret that these results are stemmed from ancillary electron-transfer pathway through specific interaction between a sulfur atom in the bridge of Zn5S and the TiO2 surface. Optical spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, density functional theory calculations, and photovoltaic measurements under standard AM 1.5 conditions were employed to support our proposal.

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Fullerene-encapsulating single-walled carbon nanotubes (C(60)@SWNT) linked with porphyrins by a short bridge have been prepared for the first time. Steady state and time-resolved spectroscopies demonstrated the initial formation of an exciplex state, followed by a charge-separated state.