No abstract

Polyoxometalate molybdenum blue (MB) complexes typically exist as discrete multianionic clusters and are composed of repeating Mo building units. MB wheels such as {Mo 176 } and {Mo 154 } are made from pentagon-centered {Mo 8 } building blocks joined by equal number of {Mo 1 } units as loin, and {Mo 2 } dimer units as skirt along the ring edge, with the ring sizes of the MB wheels modulated by the {Mo 2 } units. Herein we report a new class of contracted lanthanide-doped MB structures that have replaced all the {Mo 2 } units with lanthanide ions on the inner rim, giving the general formula {Mo 90 Ln 10 }. We show three examples of this new decameric {Mo 90 Ln 10 } (Ln = La, Ce, and Pr) framework synthesized by high temperature reduction and demonstrate that later Ln ions result in {Mo 92 Ln 9 } (Ln = Nd, Sm), conserving one {Mo 2 } linker unit in its structure, as a consequence of the lanthanide contraction. Remarkably the {Mo 90 Ln 10 } compounds are the first examples of chargeneutral molybdate wheels as confirmed by BVS, solubility experiments, and redox titrations. We detail our full synthetic optimization for the isolation of these clusters and complete characterization by X-ray, TGA, UV-vis, and ICP studies. Finally, we show that this fine-tuned self-assembly process can be utilized to selectively enrich Ln-MB wheels for effective separation of lanthanides.

Get cross! A cruciform 6,6′‐dipentacenyl, Dip‐TIPS, was prepared as a unique semiconductor with two‐dimensional isotropic face‐to‐face π‐stacking in the crystal structure. High FET mobilities were obtained from the vapor‐deposited thin films. The use of cruciform molecules in the design of organic semiconductors is a new concept that is expected to diminish the effect of molecular orientation on device performance.

No abstract

A facile route has been developed for the preparation of a new family of contorted 1.2,3.4,7.8,9.10-tetrabenzocoronenes (TBCs). A two-step cyclization reaction, i.e., oxidative photocyclization followed by FeCl(3)-mediated intramolecular cyclodehydrogenation, was carried out on the olefin precursors to obtain the final TBC compounds. These new TBC molecules have contorted conformation due to steric overcrowding as disclosed by single-crystal crystallographic analysis. Nevertheless, they showed extended π-conjugation compared with coronene and exhibited strong aggregation in solution. The thermal behavior and self-assembly of TBC-C8 in solid were studied by a combination of thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). Compound TBC-C8 showed very good thermal and photostability and exhibited long-range ordered π-stacking in the bulk state. Moreover, uniform nanofibers with tens of micrometer length are formed in the drop-casted thin films. TBC-C8 also possesses a desirable HOMO energy level (-5.10 eV), which allows efficient charge injection from electrodes such as gold electrode. The charge carrier mobilities were determined by using the space-charge limited-current (SCLC) technique and high average hole mobility of 0.61 cm(2) V(-1) s(-1) was obtained for TBC-C8.