Supramolecular phthalocyanine dimers based on the secondary dialkylammonium cation/dibenzo-24-crown-8 recognition motif

[formula: see text] New unsymmetrically substituted DB24C8-phthalocyanines, which are able to form complexes with suitable dialkylammonium cations, have been prepared. These complexes most probably have a pseudorotaxane geometry.     

Coordination of 9-ethylguanine to the mixed-ligand compound alpha-[Ru(azpy)(bpy)Cl2] (azpy = 2-phenylazopyridine and bpy = 2,2'-bipyridine). An unprecedented ligand positional shift, correlated to the cytotoxicity of this type of [RuL2Cl2] (with L = azpy or bpy) complex

The striking difference in cytotoxic activity between the inactive cis-[Ru(bpy)(2)Cl(2)] and the recently reported highly cytotoxic alpha-[Ru(azpy)(2)Cl(2)] (alpha indicating the isomer in which the coordinating Cl atoms, pyridine nitrogens, and azo nitrogens are in mutual cis, trans, cis orientation) encouraged the synthesis of the mixed-ligand compound cis-[Ru(azpy)(bpy)Cl(2)]. The synthesis and characterization of the only occurring isomer, i.e., alpha-[Ru(azpy)(bpy)Cl(2)], 1 (alpha denoting the isomer in which the Cl ligands are cis related to each other and the pyridine ring of azpy is trans to the pyridine ring of bpy), are described. The solid-state structure of 1 has been determined by X-ray structure analysis. The IC(50) values obtained for several human tumor cell lines have indicated that compound 1 shows mostly a low to moderate cytotoxicity. The binding of the DNA model base 9-ethylguanine (9-EtGua) to the hydrolyzed species of 1 has been studied and compared to DNA model base binding studies of cis-[Ru(bpy)(2)Cl(2)] and alpha-[Ru(azpy)(2)Cl(2)]. The completely hydrolyzed species of 1, i.e., alpha-[Ru(azpy)(bpy)(H(2)O)(2)](2+), has been reacted with 9-EtGua in water at room temperature for 24 h. This resulted in the monofunctional binding of only one 9-EtGua, coordinated via the N7 atom. The product has been isolated as alpha-[Ru(azpy)(bpy)(9-EtGua)(H(2)O)](PF(6))(2), 2, and characterized by 2D NOESY NMR spectroscopy. The NOE data show that the 9-EtGua coordinates (under these conditions) at the position trans to the azo nitrogen atom. Surprisingly, time-dependent (1)H NMR data of the 9-EtGua adduct 2 in acetone-d(6) show an unprecedented positional shift of the 9-EtGua from the position trans to the azo nitrogen to the position trans to the bpy nitrogen atom, resulting in the adduct alpha'-[Ru(azpy)(bpy)(9-EtGua)(H(2)O)](PF(6))(2) (alpha' indicating 9-EtGua is trans to the bpy nitrogen). This positional isomerization of 9-EtGua is correlated to the cytotoxicity of 1 in comparison to both the cytotoxicity and 9-EtGua coordination of cis-[Ru(bpy)(2)Cl(2)], alpha-[Ru(azpy)(2)Cl(2)], and beta-[Ru(azpy)(2)Cl(2)]. This positional isomerization process is unprecedented in model base metal chemistry and could be of considerable biological significance.     

Ferromagnetic spin alignment in head-to-tail coupled oligo(1, 4-phenyleneethynylene)s and Oligo(1,4-phenylenevinylene)s bearing pendant p-phenylenediamine radical cations

The intramolecular and long-range ferromagnetic coupling between p-phenylenediamine radical cations in head-to-tail coupled oligo(1, 4-phenyleneethynylene)s and oligo(1,4-phenylenvinylene)s between neighbors and next-nearest neighbors is described. UV/vis/near-IR experiments show that the radical cations are localized in the pendant p-phenylenediamine units of the conjugated oligomers. The ESR spectra of these oligo(1,4-phenyleneethynylene) and oligo(1, 4-phenylenvinylene) di(radical cation)s are consistent with those of a triplet state. A linear behavior is observed for the doubly integrated ESR intensity of the DeltaM(s) = +/-1 and DeltaM(s) = +/-2 signals with the inverse temperature (I approximately 1/T), consistent with Curie's law. This behavior indicates a triplet ground-state diradical with a large triplet-singlet energy gap or possibly a degeneracy of singlet and triplet states.     

Intuitionistic Quantum Logic of an <Emphasis Type="Italic">n</Emphasis>-level System

A decade ago, Isham and Butterfield proposed a topos-theoretic approach to quantum mechanics, which meanwhile has been extended by Döring and Isham so as to provide a new mathematical foundation for all of physics. Last year, three of the present authors redeveloped and refined these ideas by combining the C*-algebraic approach to quantum theory with the so-called internal language of topos theory (Heunen et al. in arXiv:0709.4364). The goal of the present paper is to illustrate our abstract setup through the concrete example of the C*-algebra M _n (?) of complex n×n matrices. This leads to an explicit expression for the pointfree quantum phase space Σ _n and the associated logical structure and Gelfand transform of an n-level system. We also determine the pertinent non-probabilisitic state-proposition pairing (or valuation) and give a very natural topos-theoretic reformulation of the Kochen–Specker Theorem.In our approach, the nondistributive lattice ?(M _n (?)) of projections in M _n (?) (which forms the basis of the traditional quantum logic of Birkhoff and von Neumann) is replaced by a specific distributive lattice \(\mathcal{O}(\Sigma_{n})\) of functions from the poset \(\mathcal{C}(M_{n}(\mathbb{C}))\) of all unital commutative C*-subalgebras C of M _n (?) to ?(M _n (?)). The lattice \(\mathcal{O}(\Sigma_{n})\) is essentially the (pointfree) topology of the quantum phase space Σ _n , and as such defines a Heyting algebra. Each element of \(\mathcal{O}(\Sigma_{n})\) corresponds to a “Bohrified” proposition, in the sense that to each classical context \(C\in\mathcal{C}(M_{n}(\mathbb{C}))\) it associates a yes-no question (i.e. an element of the Boolean lattice ?(C) of projections in C), rather than being a single projection as in standard quantum logic. Distributivity is recovered at the expense of the law of the excluded middle (Tertium Non Datur), whose demise is in our opinion to be welcomed, not just in intuitionistic logic in the spirit of Brouwer, but also in quantum logic in the spirit of von Neumann.     

Low temperature scanning force microscopy of the Si(111)-(7x7) surface

A low temperature scanning force microscope (SFM) operating in a dynamic mode in ultrahigh vacuum was used to study the Si(111)- (7x7) surface at 7.2 K. Not only the twelve adatoms but also the six rest atoms of the unit cell are clearly resolved for the first time with SFM. In addition, the first measurements of the short range chemical bonding forces above specific atomic sites are presented. The data are in good agreement with first principles computations and indicate that the nearest atoms in the tip and sample relax significantly when the tip is within a few A of the surface.     

Raman spectroscopy with an integrated arrayed-waveguide grating

An integrated arrayed-waveguide grating fabricated in silicon-oxynitride technology is applied to Raman spectroscopy. After its validation by reproducing the well-known spectrum of cyclohexane, polarized Raman spectra are measured of extracted human teeth containing localized initial carious lesions. Excellent agreement is obtained between the spectra of healthy and carious tooth enamel measured with our integrated device and spectra recorded using a conventional Raman spectrometer. Our results represent a step toward the realization of compact, hand-held, integrated spectrometers, e.g. for the detection of dental caries at an early stage.