Mechanism for the activation of carbon monoxide via oxorhenium complexes

Activation of CO by the rhenium(V) oxo complex [(DAAm)Re(O)(CH(3))] (1) [DAAm = N,N-bis(2-arylaminoethyl)methylamine; aryl = C(6)F(5), Mes] resulted in the isolation of the rhenium(III) acetate complex [(DAAm)Re(O(2)CCH(3))(CO)] (3). The mechanistic details of this reaction were explored experimentally. The novel oxorhenium(V) acyl intermediate [(DAAm)Re(O)(C(O)CH(3))] (2) was isolated, and its reactivity with CO was investigated. An unprecedented mechanism is proposed: CO is activated by the metal oxo complex 1 and inserted into the rhenium-methyl bond to yield acyl complex 2, after which subsequent migration of the acyl ligand to the metal oxo ligand yields acetate complex 3. X-ray crystal structures of 2 and 3 are reported.     

Photobleaching of photofrin II as a means of eliminating skin photosensitivity

One of the effects of using Photofrin II as a sensitizer in clinical photodynamic therapy is skin photosensitivity. Avoiding the harmful effect of this photosensitivity typically requires the patient to remain indoors during daylight hours for 4 weeks post injection. Photosensitivity can last up to 8 weeks. A possible method of quickly eliminating skin photosensitivity is the use of photobleaching to eliminate the DHE (dihematoporphyrin ether, the active agent in Photofrin II) from the skin. The Photofrin II was used as supplied (Photomedica, Raritan, NJ) and will be referred to as DHE. We report a series of experiments using Swiss mice which demonstrate the ability to reduce the period of photosensitivity to 1 week. The Swiss mice received 5 mg kg^-1 DHE intraperitoneal. Beginning at 24 h post injection they were given daily increasing light doses starting with 18 J cm^-2 (at 630 nm). Only the left hind feet were treated with light. At 7 days post injection both hind feet were treated with 135 J cm^-2. The pretreated left foot showed no reaction to this treatment whereas the right foot reacted as strongly as control mice which had received no pretreatment with light. The control mice were also injected 7 days prior to treatment. As a check for tolerance animals received a second injection of 5 mg kg^-1 DHE intraperitoneally 96 h after the conclusion of the bleaching protocol. Twenty-four h later the left hind foot (previously desensitized by light) reacted to 135 J cm^-2 as strongly as controls which had received the 5 mg kg^-1 of DHE but no pretreatment.     

Validating Eaton's Hypothesis: Cubane as a Benzene Bioisostere

Pharmaceutical and agrochemical discovery programs are under considerable pressure to meet increasing global demand and thus require constant innovation. Classical hydrocarbon scaffolds have long assisted in bringing new molecules to the market place, but an obvious omission is that of the Platonic solid cubane. Eaton, however, suggested that this molecule has the potential to act as a benzene bioisostere. Herein, we report the validation of Eaton's hypothesis with cubane derivatives of five molecules that are used clinically or as agrochemicals. Two cubane analogues showed increased bioactivity compared to their benzene counterparts whereas two further analogues displayed equal bioactivity, and the fifth one demonstrated only partial efficacy. Ramifications from this study are best realized by reflecting on the number of bioactive molecules that contain a benzene ring. Substitution with the cubane scaffold where possible could revitalize these systems, and thus expedite much needed lead candidate identification.     

Addition of S-H bonds across electron-deficient olefins catalyzed by well-defined copper(I) thiolate complexes

A series of monomeric (NHC)Cu(SR) (R = Ph or CH2Ph; NHC = N-heterocyclic carbene) complexes have been synthesized and fully characterized including single-crystal X-ray diffraction studies. These complexes catalyze the addition of S-H bonds across electron-deficient olefins to regioselectively produce "anti-Markovnikov" products.     

J/psi production versus transverse momentum and rapidity in p+p collisions at square root s=200 GeV

J/psi production in p+p collisions at square root s=200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over a rapidity range of -2.2相似文献   

Elliptic flow for phi mesons and (anti)deuterons in Au+Au collisions at square root of sNN=200 GeV

Differential elliptic flow (v(2)) for phi mesons and (anti)deuterons (d)d is measured for Au+Au collisions at square root of sNN=200 GeV. The v(2) for phi mesons follows the trend of lighter pi+/- and K+/- mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v(2) values for (d)d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v(2) per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.     

Unexpected Self‐Sorting Self‐Assembly Formation of a [4:4] Sulfate:Ligand Cage from a Preorganized Tripodal Urea Ligand

The design and synthesis of tripodal ligands 1 – 3 based upon the N‐methyl‐1,3,5‐benzenetricarboxamide platform appended with three aryl urea arms is reported. This ligand platform gives rise to highly preorganized structures and is ideally suited for binding SO₄^2? and H₂PO₄^? ions through multiple hydrogen‐bonding interactions. The solid‐state crystal structures of 1 – 3 with SO₄^2? show the encapsulation of a single anion within a cage structure, whereas the crystal structure of 1 with H₂PO₄^? showed that two anions are encapsulated. We further demonstrate that ligand 4 , based on the same platform but consisting of two bis‐urea moieties and a single ammonium moiety, also recognizes SO₄^2? to form a self‐assembled capsule with [4:4] SO₄^2?: 4 stoichiometry in which the anions are clustered within a cavity formed by the four ligands. This is the first example of a self‐sorting self‐assembled capsule where four tetrahedrally arranged SO₄^2? ions are embedded within a hydrophobic cavity.     

Phonon-induced Rabi-frequency renormalization of optically driven single InGaAs/GaAs quantum dots

We study optically driven Rabi rotations of a quantum dot exciton transition between 5 and 50 K, and for pulse areas of up to 14π. In a high driving field regime, the decay of the Rabi rotations is nonmonotonic, and the period decreases with pulse area and increases with temperature. By comparing the experiments to a weak-coupling model of the exciton-phonon interaction, we demonstrate that the observed renormalization of the Rabi frequency is induced by fluctuations in the bath of longitudinal acoustic phonons, an effect that is a phonon analogy of the Lamb shift.