Signaling Recognition Events with Fluorescent Sensors and Switches.

In this contribution to the special software-centered issue, the ORCA program package is described. We start with a short historical perspective of how the project began and go on to discuss its current feature set. ORCA has grown into a rather comprehensive general-purpose package for theoretical research in all areas of chemistry and many neighboring disciplines such as materials sciences and biochemistry. ORCA features density functional theory, a range of wavefunction based correlation methods, semi-empirical methods, and even force-field methods. A range of solvation and embedding models is featured as well as a complete intrinsic to ORCA quantum mechanics/molecular mechanics engine. A specialty of ORCA always has been a focus on transition metals and spectroscopy as well as a focus on applicability of the implemented methods to "real-life" chemical applications involving systems with a few hundred atoms. In addition to being efficient, user friendly, and, to the largest extent possible, platform independent, ORCA features a number of methods that are either unique to ORCA or have been first implemented in the course of the ORCA development. Next to a range of spectroscopic and magnetic properties, the linear- or low-order single- and multi-reference local correlation methods based on pair natural orbitals (domain based local pair natural orbital methods) should be mentioned here. Consequently, ORCA is a widely used program in various areas of chemistry and spectroscopy with a current user base of over 22 000 registered users in academic research and in industry.

The ORCA quantum chemistry program package

ion step. The reactivity of pMMO has been also explored by Chan,525 by means of DFT calculations on small models of Figure 116. Nonradical mechanism proposed in the Yoshizawa model of sMMO. Figure 117. Mononuclear and dinuclear models of the copper active sites of pMMO. CsH Bond Activation in Transition Metal Species Chemical Reviews, 2010, Vol. 110, No. 2 813

C-H bond activation in transition metal species from a computational perspective

A quantitative theory of the isotropic electron‐nuclear spin interactions of carbon 13 in pi‐electron radicals is presented and applied to the hyperfine splittings observed in the electron spin resonance spectra of these substances. The splittings arise from sigma‐pi interactions which polarize both the 1s and 2s electrons. The 1s‐orbital spin polarization is shown to contribute a term of negative sign with a magnitude comparable to that from the 2s electrons. For an sp2 hybridized carbon atom that is bonded to three atoms, Xi (i=1, 2, 3), the hyperfine constant aC has the form aC=(SC+ ∑ i=13QCXiC)ρπ+ ∑ i=13QXiCCρiπ, where ρπ and ρiπ(i=1,2,3) are the pi‐electron spin densities on atoms C and Xi, respectively. The contribution of the 1s electrons is determined by SC and that of the 2s electrons by the Q's, where QBCA is the sigma‐pi parameter for the nucleus of atom A resulting from the interaction between the bond BC and the pi‐electron spin density on atom B. Calculations for a planar CHC2 fragment model...

THEORETICAL INTERPRETATION OF CARBON-13 HYPERFINE INTERACTIONS IN ELECTRON SPIN RESONANCE SPECTRA. Technical Note Report No. 9

Synthetic models for heme-copper oxidases.

The volatile zinc thiolato complex Zn(SAr[double prime])[sub 2] (1) (Ar[double prime] = C[sub 6]H[sub 2]-t-Bu[sub 3]-2,4,6) was characterized by variable-temperature and solid-state [sup 13]C CP-MAS NMR and X-ray crystallography. The compound is dimeric in the solid state, with trigonal-planar zinc coordinated to three sulfur ligands and asymmetric thiolato bridges. In benzene solution, 1 dissocites into two-coordinate monomers, while at low temperature dimeric species exist in dichloromethane or toluene. The skeletal bonding pattern and the asymmetry of the thiolato bridges are explained on the basis of EHMO calculations; the Zn-S bonds are essentially [sigma] in character, with negligible contributions from Zn-S (p-p)[sub [pi]] interactions. 23 refs., 5 figs., 6 tabs.

Three-coordinate thiolato complexes of zinc: solution and solid-state structures and EHMO analysis of the bonding pattern of [Zn(S-tert-Bu3C6H2-2,4,6)2]2

The temperature dependence of the magnetic circular dichroism spectrum of matrix-isolated [Fe(CO)4] shows that the molecule is paramagnetic.

Magnetic circular dichroism evidence for the paramagnetism of tetracarbonyliron(0): low-temperature matrix studies

Decamethylrhenocene, (η5-C5Me5)2Re

Analyse de la structure electronique du molybdenocene et du tungstenocene par dichroisme circulaire magnetique; etude des effets de couplage spin-orbite et de distorsions Jahn-Teller sur l'etat 3 E 2g et la reactivite des metallocenes d 4

Electronic structure of molybdenocene and tungstenocene: detection of paramagnetism by magnetic circular dichroism in argon matrixes

Metallocenes as reaction intermediates

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