Cleavage of an Aromatic C-C Bond in Ferrocene by Insertion of an Iridium Nitrido Nitrogen Atom.

The intermolecular cleavage of C-C bonds is a rare event. Herein, we report on a late transition-metal terminal nitrido complex, which upon oxidation undergoes insertion of the nitrido nitrogen atom into the aromatic C-C bond of ferrocene. This reaction path was confirmed through N and deuterium isotope labeling experiments of the nitrido complex and ferrocenium, respectively.

Three port logic gate using forward volume spin wave interference in a thin yttrium iron garnet film.

We demonstrate a logic gate based on interference of forward volume spin waves (FVSWs) propagating in a 54 nm thick, 100 μm wide yttrium iron garnet waveguide grown epitaxially on a garnet substrate. Two FVSWs injected by coplanar waveguides were made to interfere constructively and destructively by varying their phase difference, showing an XNOR logic function. The reflected and resonant waves generated at the edges of the waveguide were suppressed using spin wave absorbers.

Multistate Multiconfiguration Quantum Chemical Computation of the Two-Photon Absorption Spectra of Bovine Rhodopsin.

Recently, progress in IR sources has led to the discovery that humans can detect infrared (IR) light. This is hypothesized to be due to the two-photon absorption (TPA) events promoting the retina dim-light rod photoreceptor rhodopsin to the same excited state populated via one-photon absorption (OPA). Here, we combine quantum mechanics/molecular mechanics and extended multiconfiguration quasi-degenerate perturbation theory calculations to simulate the TPA spectrum of bovine rhodopsin (Rh) as a model for the human photoreceptor.

The role of Snell's law for a magnonic majority gate.

In the fifty years since the postulation of Moore's Law, the increasing energy consumption in silicon electronics has motivated research into emerging devices. An attractive research direction is processing information via the phase of spin waves within magnonic-logic circuits, which function without charge transport and the accompanying heat generation. The functional completeness of magnonic logic circuits based on the majority function was recently proved.

Communication: An efficient approach to compute state-specific nuclear gradients for a generic state-averaged multi-configuration self consistent field wavefunction.

We present a new, very efficient semi-numerical approach for the computation of state-specific nuclear gradients of a generic state-averaged multi-configuration self consistent field wavefunction. Our approach eliminates the costly coupled-perturbed multi-configuration Hartree-Fock step as well as the associated integral transformation stage. The details of the implementation within the Firefly quantum chemistry package are discussed and several sample applications are given.

Shape of Multireference, Equation-of-Motion Coupled-Cluster, and Density Functional Theory Potential Energy Surfaces at a Conical Intersection.

We report and characterize ground-state and excited-state potential energy profiles using a variety of electronic structure methods along a loop lying on the branching plane associated with a conical intersection (CI) of a reduced retinal model, the penta-2,4-dieniminium cation (PSB3). Whereas the performance of the equation-of-motion coupled-cluster, density functional theory, and multireference methods had been tested along the excited- and ground-state paths of PSB3 in our earlier work, the ability of these methods to correctly describe the potential energy surface shape along a CI branching plane has not yet been investigated. This is the focus of the present contribution.

Mapping the Excited State Potential Energy Surface of a Retinal Chromophore Model with Multireference and Equation-of-Motion Coupled-Cluster Methods.

The photoisomerization of the retinal chromophore of visual pigments proceeds along a complex reaction coordinate on a multidimensional surface that comprises a hydrogen-out-of-plane (HOOP) coordinate, a bond length alternation (BLA) coordinate, a single bond torsion and, finally, the reactive double bond torsion. These degrees of freedom are coupled with changes in the electronic structure of the chromophore and, therefore, the computational investigation of the photochemistry of such systems requires the use of a methodology capable of describing electronic structure changes along all those coordinates. Here, we employ the penta-2,4-dieniminium (PSB3) cation as a minimal model of the retinal chromophore of visual pigments and compare its excited state isomerization paths at the CASSCF and CASPT2 levels of theory.

C20H4(C4F8)3: a fluorine-containing annulated corannulene that is a better electron acceptor than C60.

At sixes and sevens: The reaction of corannulene with 35 equivalents of 1,4-C4F8I2 is an efficient and a relatively selective process that yields two main products in which six H atoms are substituted with three C4F8 moieties that form six- and seven-membered rings. Low-temperature photoelectron spectroscopy showed the electron affinity of the major isomer (shown) exceeds that of C60 (2.74±0.

Dynamic Electron Correlation Effects on the Ground State Potential Energy Surface of a Retinal Chromophore Model.

The ground state potential energy surface of the retinal chromophore of visual pigments (e.g., bovine rhodopsin) features a low-lying conical intersection surrounded by regions with variable charge-transfer and diradical electronic structures.

Phase transitions, magnetotransport and magnetocaloric effects in a new family of quaternary Ni-Mn-In-Z Heusler alloys.

The magnetic, magnetotransport, and magnetocaloric properties near compound phase transitions in Ni50Mn35In14Z (Z = In, Ge, Al), and Ni48Co2Mn35In15 Heusler alloys have been studied using VSM and SQUID magnetometers (at magnetic fields (H) up to 5 T), four-probe method (at H = 0.005-1.5 T), and an adiabatic magnetocalorimeter (for H changes up to deltaH = 1.

Photoisomerization around a fulvene double bond: coherent population transfer to the electronic ground state?

Photoisomerization around a central fulvene-type double bond is known to proceed through a conical intersection at the perpendicular geometry. The process is studied with an indenylidene-dihydropyridine model compound, allowing the use of visible excitation pulses. Transient absorption shows that 1) stimulated emission shifts to the red and loses oscillator strength on a 50 fs timescale, and 2) bleach recovery is highly nonexponential and not affected by solvent viscosity or methyl substitution at the dihydropyridine ring.

Extended multi-configuration quasi-degenerate perturbation theory: the new approach to multi-state multi-reference perturbation theory.

The distinctive desirable features, both mathematically and physically meaningful, for all partially contracted multi-state multi-reference perturbation theories (MS-MR-PT) are explicitly formulated. The original approach to MS-MR-PT theory, called extended multi-configuration quasi-degenerate perturbation theory (XMCQDPT), having most, if not all, of the desirable properties is introduced. The new method is applied at the second order of perturbation theory (XMCQDPT2) to the 1(1)A(')-2(1)A(') conical intersection in allene molecule, the avoided crossing in LiF molecule, and the 1(1)A(1) to 2(1)A(1) electronic transition in cis-1,3-butadiene.

Gas phase absorption studies of photoactive yellow protein chromophore derivatives.

Photoabsorption spectra of deprotonated trans p-coumaric acid and two of its methyl substituted derivatives have been studied in gas phase both experimentally and theoretically. We have focused on the spectroscopic effect of the location of the two possible deprotonation sites on the trans p-coumaric acid which originate to either a phenoxide or a carboxylate. Surprisingly, the three chromophores were found to have the same absorption maximum at 430 nm, in spite of having different deprotonation positions.

Modeling photoabsorption of the asFP595 chromophore.

The fluorescent protein asFP595 is a promising photoswitchable biomarker for studying processes in living cells. We present the results of a high level theoretical study of photoabsorption properties of the model asFP595 chromophore molecule in biologically relevant protonation states: anionic, zwitterionic, and neutral. Ground state equilibrium geometry parameters are optimized in the PBE0/(aug)-cc-pVDZ density functional theory approximation.

An opsin shift in rhodopsin: retinal S0-S1 excitation in protein, in solution, and in the gas phase.

We considered a series of model systems for treating the photoabsorption of the 11-cis retinal chromophore in the protonated Schiff-base form in vacuum, solutions, and the protein environment. A high computational level, including the quantum mechanical-molecular mechanical (QM/MM) approach for solution and protein was utilized in simulations. The S0-S1 excitation energies in quantum subsystems were evaluated by means of an augmented version of the multiconfigurational quasidegenerate perturbation theory (aug-MCQDPT2) with the ground-state geometry parameters optimized in the density functional theory PBE0/cc-pVDZ approximation.

Anomalous Faraday effect of a system with extraordinary optical transmittance.

It is shown theoretically that the Faraday rotation becomes anomalously large and exhibits extraordinary behavior near the frequencies of the extraordinary optical transmittance through optically thick perforated metal film with holes filled with a magneto-optically active material. This phenomenon is explained as result of strong confinement of the evanescent electromagnetic field within magnetic material, which occurs due to excitation of the coupled plasmon-polaritons on the opposite surfaces of the film.