physicochemical properties in the crystalline bulk and in thin films deposited from the gas phase

Four analogues of the spin-crossover complex [Fe(H2Bpz2)2(phen)] (H2Bpz2 = dihydrobis(pyrazolyl)borate; 2) containing functionalized 1,10-phenanthroline (phen) ligands have been prepared; i.e., [Fe(H2Bpz2)2(L)], L = 4-methyl-1,10-phenanthroline (3), 5-chloro-1,10-phenanthroline (4), 4,7-dichloro-1,10-phenanthroline (5), and 4,7-dimethyl-1,10-phenanthroline (6). The systems are investigated by magnetic susceptibility measurements and a range of spectroscopies in the solid state and in thin films obtained by physical vapour deposition (PVD). Thermal as well as light-induced SCO behaviour is observed for 3–6 in the films. By contrast, thermal SCO in the solid state occurs only for 3 and 4 but is absent for 5 and 6. These findings are discussed in the light of cooperative and intermolecular interactions

c-erbB2 and topoisomerase IIα protein expression independently predict poor survival in primary human breast cancer: a retrospective study

INTRODUCTION: c-erbB2 (also known as HER-2/neu) and topoisomerase IIα are frequently overexpressed in breast cancer. The aim of the study was to analyze retrospectively whether the expression of c-erbB2 and topoisomerase IIα protein influences the long-term outcome of patients with primary breast cancer. METHODS: In this study c-erbB2 and topoisomerase IIα protein were evaluated by immunohistochemistry in formalin-fixed paraffin-embedded tissue from 225 samples of primary breast cancer, obtained between 1986 and 1998. The prognostic value of these markers was analyzed. RESULTS: Of 225 primary breast tumor samples, 78 (34.7%) showed overexpression of either c-erbB2 (9.8%) or topoisomerase IIα protein (24.9%), whereas in 21 tumors (9.3%) both proteins were found to be overexpressed. Patients lacking both c-erbB2 and topoisomerase IIα overexpression had the best long-term survival. Overexpression of either c-erbB2 or topoisomerase IIα was associated with shortened survival, whereas patients overexpressing both c-erbB2 and topoisomerase IIα showed the worst disease outcome (P < 0.0001). Treatment with anthracyclines was not capable of reversing the negative prognostic impact of topoisomerase IIα or c-erbB2 overexpression. CONCLUSION: The results of this exploratory study suggest that protein expression of c-erbB2 and topoisomerase IIα in primary breast cancer tissues are independent prognostic factors and are not exclusively predictive factors for anthracycline response in patients with primary breast cancer

Detailed Pair Natural Orbital-Based Coupled Cluster Studies of Spin Crossover Energetics

In this work, a detailed study of spin-state splittings in three spin crossover model compounds with DLPNO-CCSD(T) is presented. The performance in comparison to canonical CCSD(T) is assessed in detail. It was found that spin-state splittings with chemical accuracy, compared to the canonical results, are achieved when the full iterative triples (T1) scheme and TightPNO settings are applied and relativistic effects are taken into account. Having established the level of accuracy that can be reached relative to the canonical results, we have undertaken a detailed basis set study in the second part of the study. The slow convergence of the results of correlated calculations with respect to basis set extension is particularly acute for spin-state splittings for reasons discussed in detail in this Article. In fact, for some of the studied systems, 5Z basis sets are necessary in order to come close to the basis set limit that is estimated here by basis set extrapolation. Finally, the results of the present work are compared to available literature. In general, acceptable agreement with previous CCSD(T) results is found, although notable deviations stemming from differences in methodology and basis sets are noted. It is noted that the published CASPT2 numbers are far away from the extrapolated CCSD(T) numbers. In addition, dynamic quantum Monte Carlo results differ by several tens of kcal/mol from the CCSD(T) numbers. A comparison to DFT results produced with a range of popular density functionals shows the expected scattering of results and showcases the difficulty of applying DFT to spin-state energies

Magnetic Circular Dichroism Spectrum of the Molybdenum(V) Complex [Mo(O)Cl₃dppe]: C-Term Signs and Intensities for Multideterminant Excited Doublet States

The molybdenum(V) complex [Mo(O)Cl3dppe] [dppe = 1,2-bis(diphenylphosphino)ethane] is considered as a model system for a combined study of the electronic structure using UV/vis absorption and magnetic circular dichroism (MCD) spectroscopy. In order to determine the signs and MCD C-term intensities of the chlorido → molybdenum charge-transfer transitions, it is necessary to take the splitting of the excited doublet states into sing-doublet and trip-doublet states into account. While transitions to the sing-doublet states are electric-dipole-allowed, those to the trip-doublet states are electric-dipole-forbidden. As spin–orbit coupling within the manifold of sing-doublet states vanishes, configuration interaction between the sing-doublet and trip-doublet states is required to generate the MCD C-term intensity. The most prominent feature in the MCD spectrum of [Mo(O)Cl3dppe] is a “double pseudo-A term”, which consists of two corresponding pseudo-A terms centered at 27000 and 32500 cm–1. These are assigned to the ligand-to-metal charge-transfer transitions from the pπ orbitals of the equatorial chlorido ligands to the Mo dyz and dxz orbitals. On the basis of the theoretical expressions developed by Neese and Solomon (Inorg. Chem.1999, 38, 1847−1865), a general treatment of the MCD C-term intensity of these transitions is presented that explicitly considers the multideterminant character of the excited states. The individual MCD signs are determined from the corresponding transition densities derived from the calculated molecular orbitals of the title complex (BP86/LANL2DZ)

Free Reaction Enthalpy Profile of the Schrock Cycle Derived from Density Functional Theory Calculations on the Full [Mo^HIPTN₃N] Catalyst

A series of density functional theory (DFT) calculations on the full [MoHIPTN3N] catalyst are performed to obtain an energy profile of the Schrock cycle. This is a continuation of our earlier investigation of this cycle in which the bulky hexaisopropyterphenyl (HIPT) substituents of the ligand were replaced by hydrogen atoms (Angew. Chem., Int. Ed.2005, 44, 5639). In an effort to provide a treatment that is as converged as possible from a quantum-chemical point of view, the present study now fully takes the HIPT moieties into account. Moreover, structures and energies are calculated with a near-saturated basis set, leading to models with 280 atoms and 4850 basis functions. Solvent and scalar relativistic effects have been treated using the conductor-like screening model and zeroth-order regular approximation, respectively. Free reaction enthalpies are evaluated using the PBE and B3LYP functionals. A comparison to the available experimental data reveals much better agreement with the experiment than preceding DFT treatments of the Schrock cycle. In particular, free reaction enthalpies of reduction steps and NH3/N2 exchange are now excellently reproduced

Electronic Structure, Vibrational Spectra, and Spin-Crossover Properties of Vacuum-Evaporable Iron(II) Bis(dihydrobis(pyrazolyl)borate) Complexes with Diimine Coligands. Origin of Giant Raman Features

The vibrat onal properties of spin-crossover complexes [Fe(H2B(pz)(2))(2)(L)] (pz = pyrazole) containing L = 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen) ligands are investigated by temperature-dependent infrared and Raman spectroscopy. For comparison, the analogous cobalt(II) complexes [Co(H2B(pz)(2))(2)(L)] (L = bipy and phen) and iron(II) compounds with L = 4,4'-dimethyl-2,2'-bipyridine and 4,7-dimethyl-1,10-phenanthroline coligands are studied. Highly intense, structured bands (giant Raman features, GRFs) are observed in the resonance Raman spectra of all Fe(II) complexes between 400 and 500 cm(-1) at low temperatures in the HS state which, for the SCO complexes, is excited by the Raman laser. On the basis of magnetic field Mossbauer and saturation magnetization data electronic Raman effects are excluded to account for these features. Furthermore, detailed vibrational analysis also allows excluding a vibrational resonance Raman effect involving one of the modes of the individual complexes as a possible origin of the GRFs. Consequently, these features are attributed to coherent two-phonon excitation of metal-ligand stretching vibrations in molecular dimers coupled by pi-pi stacking interactions

The phenol ortho-oxygenation by mononuclear copper(I) complexes requires a dinuclear mu-eta2:eta2-peroxodicopper(II) complex rather than mononuclear CuO2 species”

The mononuclear complex [Cu(L)]+ performs the orthooxygenation of an exogeneous phenol through the formation of a dinuclear m-h2+h2-peroxodicopper(II) intermediate, which is so far the only type of copper–dioxygen complex that mediates the tyrosinase monophenolase reactio