Enantioselective reductions of [m] ferrocenophanones

Enantioselective reductions of prochiral ferrocenophane ketones were investigated. Oxazaborolidine mediated reduction led to corresponding chiral alcohols generally in good yields and enantioselectivities up to 97% ee. Ruthenium-catalyzed transfer hydrogenation was rather unsuccessful in reducing cyclic ferrocene ketones. Proline-derived activator together with trichlorosilane also proved to be an effective method for some substrates (up to 99% ee). Pronounced tendency of α-ferrocenyl ketones toward reductive deoxygenation was studied by DFT computational methods.     

Crystal water molecules as magnetic tuners in molecular metamagnets exhibiting antiferro-ferro-paramagnetic transitions

We studied the effects of the number of crystal water molecules on the magnetic behavior of {[Ni(en)(2)](3)[Fe(CN)(6)](2)·xH(2)O}(n) (1-3) (where en = ethylenediamine and x = 3, 2, or 0) coordination polymers by (57)Fe M?ssbauer spectroscopy, single-crystal X-ray diffraction, and magnetization measurements. Magnetic phase diagrams constructed for all three compounds indicate that they behave as metamagnets exhibiting very rare field-induced antiferro-ferro-paramagnetic transitions. The number of crystal water molecules has a major effect on the Néel temperature, critical field, and magnetic hardness of the compounds in the ferromagnetic state. Moreover, the systems behave as molecular magnetic sponges, changing their magnetic properties due to the controllable and reversible dehydration/hydration process.     

Probing the aromaticity of the [(H(t)Ac)3(μ2-H)6], [(H(t)Th)3(μ2-H)6],(+), and [(H(t)Pa)3(μ2-H)6] clusters

In this study we report about the aromaticity of the prototypical [(H(t)Ac)(3)(μ(2)-H)(6)], [(H(t)Th)(3)(μ(2)-H)(6)](+), and [(H(t)Pa)(3)(μ(2)-H)(6)] clusters via two magnetic criteria: nucleus-independent chemical shifts (NICS) and the magnetically induced current density. All-electron density functional theory calculations were carried out using the two-component zeroth-order regular approach and the four-component Dirac-Coulomb Hamiltonian, including scalar and spin-orbit relativistic effects. Four-component current density maps and the integration of induced ring-current susceptibilities clearly show that the clusters [(H(t)Ac)(3)(μ(2)-H)(6)] and [(H(t)Th)(3)(μ(2)-H)(6)](+) are non-aromatic whereas [(H(t)Pa)(3)(μ(2)-H)(6)] is anti-aromatic. However, for the thorium cluster we find a discrepancy between the current density plots and the classification through the NICS index. Our results also demonstrate the increasing influence of f orbitals, on bonding and magnetic properties, with increasing atomic number in these clusters. We think that the enhanced electron mobility in [(H(t)Pa)(3)(μ(2)-H)(6)] is due the significant 5f character of its valence shell. Also the participation of f orbitals in bonding is the reason why the protactinium cluster has the shortest bond lengths of the three clusters. This study provides another example showing that the magnetically induced current density approach can give more reliable results than the NICS index.     

The ab initio calculation of molecular electric, magnetic and geometric properties

We give an account of some recent advances in the development of ab initio methods for the calculation of molecular response properties, involving electric, magnetic, and geometric perturbations. Particular attention is given to properties in which the basis functions depend explicitly both on time and on the applied perturbations such as perturbations involving nuclear displacements or external magnetic fields when London atomic orbitals are used. We summarize a general framework based on the quasienergy for the calculation of arbitrary-order molecular properties using the elements of the density matrix in the atomic-orbital basis as the basic variables. We demonstrate that the necessary perturbed density matrices of arbitrary order can be determined from a set of linear equations that have the same formal structure as the set of linear equations encountered when determining the linear response equations (or time-dependent self-consistent-field equations). Additional components needed to calculate properties involving perturbation-dependent basis sets are flexible one- and two-electron integral techniques for geometric or magnetic-field differentiated integrals; in Kohn-Sham density-functional theory (KS-DFT), we also need to calculate derivatives of the exchange-correlation functional. We describe a recent proposal for evaluating these contributions based on automatic differentiation. Within this framework, it is now possible to calculate any molecular property for an arbitrary self-consistent-field reference state, including two- and four-component relativistic self-consistent-field wave functions. Examples of calculations that can be performed with this formulation are presented.     

Synthesis of aryl(ferrocenyl)methanols via an enantioselective addition of arylboronic acids

Enantiomerically enriched ferrocenyl alcohols are important intermediates in the synthesis of a range of chiral ferrocene-derived ligands. We studied various possibilities for their synthesis by the catalytic enantioselective addition of arylboronic acids to ferrocenyl carbonyl compounds. The best system comprised of ferrocenyl oxazolinyl alcohol as a catalyst and an arylation reagent generated from a boronic acid and diethylzinc. Aryl ferrocenyl methanols were synthesized in yields of up to 97% and with enantiomeric purities of up to er 98:2.     

Implicit stress integration method of Shape Memory material model

The phenomenological SMA material model proposed by Lagoudas [1] is modified and implemented in finite element software PAK [2]. Critical thermodynamic force is derived to match implicit integration method. All variables are derived to depend on effective values of stress, strain and martensitic volume fraction. One scalar equation need to be solved in the integration point using trial stress direction for each time step. The integration in the trial deviatoric stress direction provides possibility to solve large strain problems using the algorithms developed for small strains. Two one-dimensional and one non-proportional large strain example verified accuracy of proposed modifications. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)