Group

Result H23

Synthesis of Metal–Organic Complex Arrays

P. Vairaprakash, H. Ueki, K. Tashiro, O. M. Yaghi, J. Am. Chem. Soc., 133, 759–761, 2011. Highlighted in C&EN, 89, 8, 2011.

Merrifield solid-phase peptide synthesis is a well-established synthetic technique for polypeptides, where the order in which the amino acids are added determines their sequence in the product. By taking advantage of the consecutive nature of this procedure, we have successfully produced heterometallic dyad, triad, tetrad, pentad, and hexad complexes. It was critical to confirm that no metal exchange took place during the full reaction workup procedures. Any metal exchange would give unexpected sequences with disproportionate relative metal-to-metal content. We confirmed the absence of metal exchange activity in the metal complex monomers on the basis of the fact that 1H NMR spectra of mixtures containing one of the monomers and another terpyridine ligand that were kept standing for 2 days at 25 °C showed no resonances to the demetalated ligand. We also confirmed that no other sequences with unexpected metal content were detected by mass spectroscopy of the products as-cleaved from the polymeric resins.

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Assembly and Manipulation of Rotatable Cerium Porphyrinato Sandwich Complexes on a Surface

D. Écija, W. Auwärter, S. Vijayaraghavan, K. Seufert, F. Bischoff, K. Tashiro, J. V. Barth, Angew. Chem. Int. Ed., 50, 3872–3877, 2011. Highlighted as Frontispiece Picture.

Metal bisporphyrinate double-decker compounds have been regarded as interesting candidates for molecular rotors or gears for more than a decade. We have achieved the single-molecular level control of the rotation of upper porphyrin disk of a surface-attached cerium double-decker compound by STM manipulation at very low temperatures. To prepare the monolayer of the metal complex on a silver surface for the STM experiments, Ce atomic beam was irradiated to a porphyrin precursor multilayer on the substrate under vacuum, where not only the expected species but also another product higher than that were detected. From the height analysis as well as scanning tunneling spectroscopy of that unexpected species, production of biscerium triple-decker compound, whose synthesis by the conventional solution phase approaches has kept failing so far, was strongly suggested.