Influence of the trans Substituent on N2 Bonding in Iron(ii)–Phosphane Complexes: Structure,Synthesis, and Properties of the Monomeric Adducts trans-[FeXN2(depe)2]BPh4, X=Cl,Br

Not a dimer but a monomer was found in the X-ray structure analysis of the complex “trans-[{FeCl(depe)₂}₂(µ-N₂)](BPh₄)₂” (depe=Et₂PCH₂CH₂PEt₂). The complexes [FeXN₂(depe)₂]BPh₄ (X=Cl, Br; structure of the cation for X=Cl shown on the right) are much less stable than the analogous hydride compounds and undergo N₂ exchange at room temperature even in the solid state.     

Quantum charge fluctuations and the polarizability of the single-electron box

We measure the average charge on the island of a single-electron box, with an accuracy of two thousandths of an electron. Thermal fluctuations alone cannot account for the dependence of the average charge on temperature, on external potential, or on the quasiparticle density of states in the metal from which the box is formed. In contrast, we find excellent agreement between these measurements and a theory that treats the quantum fluctuations of charge perturbatively.     

Measurement of the excited-state lifetime of a microelectronic circuit

We demonstrate that a continuously measured microelectronic circuit, the Cooper-pair box measured by a radio-frequency single-electron transistor, approximates a quantum two-level system. We extract the Hamiltonian of the circuit through resonant spectroscopy and measure the excited-state lifetime. The lifetime is more than 10(5) times longer than the inverse transition frequency of the two-level system, even though the measurement is active. This lifetime is also comparable to an estimate of the known upper limit, set by spontaneous emission, for this circuit.     

SU(2)×SU(2) ELECTROWEAK THEORY IN LEP 1 DATA ON Z PARTICLE PRODUCTION

Recent data obtained by LEP1 are discussed and their potential implication for the existence of a Z particle. This letter advocates that this fits within the basic tenet of an SU(2)×SU(2) extended theory of the standard model of electroweak interactions. This extended electroweak model is motivated by nonabelian electrodynamics that provides an effective calculus for nonlinear optics.     

Derivation of O(3) Electrodynamics from the Irreducible Representations of the Einstein Group

By considering the irreducible representations of the Einstein group (the Lie group of general relativity), Sachs [1] has shown that the electromagnetic field tensor can be developed in terms of a metric q , which is a set of four quaternion-valued components of four-vector. Using this method, it is shown that the electromagnetic field vanishes [1] in flat spacetime, and that electromagnetism in general is a non-Abelian field theory. In this paper the non-Abelian component of the field tensor is developed to show the presence of the B ⁽³⁾ field of the O(3) electrodynamics, and the basic structure of O(3) electrodynamics is shown to be a sub-structure of general relativity as developed by Sachs. The extensive empirical evidence for both theories is summarized.     

Structural and electronic characterization of non-heme Fe(II)-nitrosyls as biomimetic models of the Fe(B) center of bacterial nitric oxide reductase

The detoxification of nitric oxide (NO) by bacterial NO reductase (NorBC) has gained much attention as this reaction provides a paradigm as to how NO can be detoxified anaerobically in cells. However, a clear mechanistic picture of how the heme/non-heme active site of NorBC activates NO is lacking, mostly as a result of insufficient knowledge about the properties of the non-heme iron(II)-NO adduct. Here we report the first biomimetic model complexes for this species that closely resemble the coordination environment found in the protein, using the ligands BMPA-Pr and TPA. The systematic investigation of these compounds allowed us to gain key insight into the electronic structure and geometric properties of high-spin non-heme iron(II)-NO adducts. In particular, we show how small changes in the ligand environment of iron could be used by NorBC to greatly modulate the properties, and hence, the reactivity of this species.     

Vibrational assignments of six-coordinate ferrous heme nitrosyls: new insight from nuclear resonance vibrational spectroscopy

This Communication addresses a long-standing problem: the exact vibrational assignments of the low-energy modes of the Fe-N-O subunit in six-coordinate ferrous heme nitrosyl model complexes. This problem is addressed using nuclear resonance vibrational spectroscopy (NRVS) coupled to (15)N(18)O isotope labeling and detailed simulations of the obtained data. Two isotope-sensitive features are identified at 437 and 563 cm(-1). Normal coordinate analysis shows that the 437 cm(-1) mode corresponds to the Fe-NO stretch, whereas the 563 cm(-1) band is identified with the Fe-N-O bend. The relative NRVS intensities of these features determine the degree of vibrational mixing between the stretch and the bend. The implications of these results are discussed with respect to the trans effect of imidazole on the bound NO. In addition, a comparison to myoglobin-NO (Mb-NO) is made to determine the effect of the Mb active site pocket on the bound NO.     

Structural and Spectroscopic Characterization of a High‐Spin {FeNO}6 Complex with an Iron(IV)−NO− Electronic Structure

Although the interaction of low‐spin ferric complexes with nitric oxide has been well studied, examples of stable high‐spin ferric nitrosyls (such as those that could be expected to form at typical non‐heme iron sites in biology) are extremely rare. Using the TMG₃tren co‐ligand, we have prepared a high‐spin ferric NO adduct ({FeNO}⁶ complex) via electrochemical or chemical oxidation of the corresponding high‐spin ferrous NO {FeNO}⁷ complex. The {FeNO}⁶ compound is characterized by UV/Visible and IR spectroelectrochemistry, Mössbauer and NMR spectroscopy, X‐ray crystallography, and DFT calculations. The data show that its electronic structure is best described as a high‐spin iron(IV) center bound to a triplet NO^? ligand with a very covalent iron?NO bond. This finding demonstrates that this high‐spin iron nitrosyl compound undergoes iron‐centered redox chemistry, leading to fundamentally different properties than corresponding low‐spin compounds, which undergo NO‐centered redox transformations.