In this paper, the differences in the spectroscopic properties and electronic structures of five- and six-coordinate iron(II) porphyrin NO complexes are explored using [Fe(TPP)(NO)] (1; TPP = tetraphenylporphyrin) and [Fe(TPP)(MI)(NO)] (2; MI = 1-methylimidazole) type systems. Binding of N-donor ligands in axial position trans to NO to five-coordinate complexes of type 1 is investigated using UV-vis absorption and 1H NMR spectroscopies. This way, the corresponding binding constants Keq are determined and the 1H NMR spectra of 1 and 2 are assigned for the first time. In addition, 1H NMR allows for the determination of the degree of denitrosylation in solutions of 1 with excess base. The influence of the axial ligand on the properties of the coordinated NO is then investigated. Vibrational spectra (IR and Raman) of 1 and 2 are presented and assigned using isotope substitution and normal-coordinate analysis. Obtained force constants are 12.53 (N-O) and 2.98 mdyn/A (Fe-NO) for 1 compared to 11.55 (N-O) and 2.55 mdyn/A (Fe-NO) for 2. Together with the NMR results, this provides experimental evidence that binding of the trans ligand weakens the Fe-NO bond. The principal bonding schemes of 1 and 2 are very similar. In both cases, the Fe-N-O subunit is strongly bent. Donation from the singly occupied pi* orbital of NO into d(z2) of iron(II) leads to the formation of an Fe-NO sigma bond. In addition, a medium-strong pi back-bond is present in these complexes. The most important difference in the electronic structures of 1 and 2 occurs for the Fe-NO sigma bond, which is distinctively stronger for 1 in agreement with the experimental force constants. The increased sigma donation from NO in 1 also leads to a significant transfer of spin density from NO to iron, as has been shown by magnetic circular dichroism (MCD) spectroscopy in a preceding Communication (Praneeth, V. K. K.; Neese, F.; Lehnert, N. Inorg. Chem. 2005, 44, 2570-2572). This is confirmed by the 1H NMR results presented here. Hence, further experimental and computational evidence is provided that complex 1 has noticeable Fe(I)NO+ character relative to 2, which is an Fe(II)NO(radical) complex. Finally, using MCD theory and quantum chemical calculations, the absorption and MCD C-term spectra of 1 and 2 are assigned for the first time.

We have calculated the leading-twist next-to-leading order (NLO), i.e., O(α s ), correction to the light-cone sum rules prediction for the electromagnetic form factors of the nucleon. We have used the Ioffe nucleon interpolation current and worked in M N = 0 approximation, with M N being the mass of the nucleon. In this approximation, only the Pauli form factor F 2 receives a correction and the calculated correction is quite sizable (cca 60%). The numerical results for the proton form factors show the improved agreement with the experimental data. We also discuss the problems encountered when going away from M N = 0 approximation at NLO, as well as, gauge invariance of the perturbative results. This work presents the first step towards the NLO accuracy in the light-cone sum rules for baryon form factors.

Ready…︁ steady…︁ go! The copper(I) complex 1 not only catalyzes the oxygenation of di‐tert‐butylphenol (DTBP‐H) to di‐tert‐butylquinone (DTBQ) in a tyrosinase‐like fashion, but also allows the reactive cycle to be studied in a stepwise and controlled manner. This feature opens new insights into the individual stages of the tyrosinase reaction, phenol hydroxylation, and release of the product as quinone. The implications for the enzymatic reaction are discussed.

A theoretical framework is suggested for the calculation of N ! transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the soft contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The minus components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentum.

The synthesis and physicochemical properties of the new molybdenum dinitrogen complexes [Mo(N 2 )(tdppme)-(dmpm)] (2) and [Mo(N 2 )(tdppme)(dppm)] (3) are reported. Complexes 2 and 3 are facially coordinated by the tripodal ligand 1,1,1-tris(diphenylphosphanylmethyl)ethane (tdppme) and contain the bidentate coligands bis(dimethylphosphanyl)methane (dmpm) and bis(diphenylphosphanyl)-methane (dppm), respectively. They are accessible by amalgam reduction of the Mo III precursor [MoBr 3 (tdppme)] (1) under nitrogen in the presence of dppm and dmpm, respectively. Protonation of 2 with trifluoromethanesulfonic acid