Direct Observation of the Binding Mode of the Phosphonate Anchor to Nanosized Polyoxotitanate Clusters

The structures of three newly synthesized phosphonate‐substituted polyoxotitanates are reported. The Ti/O core of [Ti₄O(OEt)₁₂(PhenylPO₃)] ( 1 ) is the building block for two larger phosphonate‐substituted nanoclusters, [Ti₂₅O₂₆(OEt)₃₆(PhenylPO₃)₆] ( 2 ) and [Ti₂₆O₂₆(OEt)₃₉(PhenylPO₃)₆]Br ( 3 ). All compounds exhibit a not previously recognized triply bridging binding mode of the phosphonate anchor with short connecting Ti? O bonds, the average of which is 2.010(7) Å. Comparison with previously reported work suggests that the binding mode of the phosphonate anchor is strongly dependent on the structure of the underlying substrate.     

Radioaktive Untersuchungen

Ohne Zusammenfassung     

Restricted photochemistry in the molecular solid state: structural changes on photoexcitation of Cu(I) phenanthroline metal-to-ligand charge transfer (MLCT) complexes by time-resolved diffraction

The excited-state structure of [Cu(I)[(1,10-phenanthroline-N,N') bis(triphenylphosphine)] cations in their crystalline [BF(4)] salt has been determined at both 180 and 90 K by single-pulse time-resolved synchrotron experiments with the modified polychromatic Laue method. The two independent molecules in the crystal show distortions on MLCT excitation that differ in magnitude and direction, a difference attributed to a pronounced difference in the molecular environment of the two complexes. As the excited states differ, the decay of the emission is biexponential with two strongly different lifetimes, the longer lifetime, assigned to the more restricted molecule, becoming more prevalent as the temperature increases. Standard deviations in the current Laue study are very much lower than those achieved in a previous monochromatic study of a Cu(I) 2,9-dimethylphenanthroline substituted complex ( J. Am. Chem. Soc. 2009 , 131 , 6566 ), but the magnitudes of the shifts on excitation are similar, indicating that lattice restrictions dominate over the steric effect of the methyl substitution. Above all, the study illustrates emphatically that molecules in solids have physical properties different from those of isolated molecules and that their properties depend on the specific molecular environment. This conclusion is relevant for the understanding of the properties of molecular solid-state devices, which are increasingly used in current technology.     

Operator algebras and a theorem of Dieudonne

LetA be aC*-algebra with second dualA″. Let (φ _n)(n=1,...) be a sequence in the dual ofA such that limφ _n(a) exists for eacha εA. In general, this does not imply that limφ _n(x) exists for eachx εA″. But if limφ _n(p) exists whenever p is the range projection of a positive self-adjoint element of the unit ball ofA, then it is shown that limφ _n(x) does exist for eachx inA″. This is a non-commutative generalisation of a celebrated theorem of Dieudonné. A new proof of Dieudonné’s theorem, for positive measures, is given here. The proof of the main result makes use of Dieudonné’s original theorem.