Search results for "Inorganic compound"
showing 10 items of 124 documents
Mossbauer spectroscopic study of the thermal spin crossover in [Fe(II)(isoxazole)(6)](ClO(4))(2)
2008
The (57)Fe Mossbauer spectroscopy of mononuclear [Fe(II)(isoxazole)(6)](ClO(4))(2) has been studied to reveal the thermal spin crossover of Fe(II) between low-spin (S = 0) and high-spin (S = 2) states.Temperature-dependent spin transition curves have been constructed with the least-square fitted data obtained from the Mossbauer spectra measured at various temperatures between 84 and 270 K during a cooling and heating cycle. This compound exhibits an unusual temperature-dependent spin transition behaviour with T(C)(down arrow) = 223 and T(C)(up arrow) = 213 K occurring in the reverse order in comparison to those observed in SQUID observation and many other spin transition compounds. The comp…
Electronic structure of phthalocyanines : Theoretical investigation of the optical properties of phthalocyanine monomers, dimers, and crystals
1990
We present valence effective Hamiltonian (VEH) calculations on the optical absorptions of a series of phthalocyanine compounds: the metal‐free phthalocyanine molecule, a model system for the lithium phthalocyanine molecule, the metal‐free phthalocyanine dimer, and model systems for the lutetium diphthalocyanine and the lithium phthalocyanine crystal. For these compounds, it is found that the major factor influencing the evolution of the optical transitions is not the electronic structure of the metal but rather the geometric structure: phthalocyanine intraring geometry and, in the dimers and crystals, interring separation and staggering angle. The origin of the so‐called Soret or B absorpti…
Preparation and Characterization of P2 BCh Ring Systems (Ch=S, Se) and Their Reactivity with N-Heterocyclic Carbenes
2018
Four-membered rings with a P2BCh core (Ch = S, Se) have been synthesized via reaction of phosphinidene chalcogenide (Ar*P=Ch) and phosphaborene (Mes*P=BNR2). The mechanistic pathways towards these rings are explained by detailed computational work that confirmed the preference for the formation of P–P, not P–B, bonded systems, which seems counterintuitive given that both phosphorus atoms contain bulky ligands. The reactivity of the newly synthesized heterocycles, as well as that of the known (RPCh)n rings (n = 2, 3), was probed by the addition of Nheterocyclic carbenes, which revealed that all investigated compounds can act as sources of low-coordinate phosphorus species. peerReviewed
Reversible switching of the electronic ground state in a pentacoordinated Cu(ii) complex.
2013
International audience; An easy reversible switching of the electronic ground state in a pentacoordinated copper(ii) complex is reported for the first time. The simple protonation of a carboxylic group in a Cu(ii) complex with a {dx(2)-y(2)}(1) electronic configuration leads to a flip of the ground electronic configuration from {dx(2)-y(2)}(1) to {dz(2)}(1) in the metal ion.
Mechanism of self-trapped hole motion in corundum crystals
1993
Abstract Atomistic simulations of the self-trapped hole eauilibrium geometry and migration in a pure corundum crystal have been carried out using the semiempirical method of intermedia te neglect of differential overlap and atom-atom potentials, as implemented in the CASCADE code. The activation energies for three different hole-hopping mechanisms are calculated. It is shown that the 60° reorientations of a self-trapped hole and hopping to the nearest O-atom triangle reauire almost the same activation energy, approximately 0.9 eV, which agrees auite well with the experi-mental value for hole migration of 0.7 eV. A new mechanism of small-polaron motion is suggested.
Dipolar and Quadrupolar Freezing in(KBr)1−x(KCN)x
1986
Dipolar and quadrupolar susceptibility measurements are reported for the molecular glass system ${(\mathrm{KBr})}_{1\ensuremath{-}x}{(\mathrm{KCN})}_{x}$ covering a wide range of frequencies. The results allow a direct comparison of the dipolar and quadrupolar anomalies and demonstrate unambiguously that the freezing in of the dipolar and quadrupolar degrees of freedom occurs at different temperatures.
Spin dependence of low energy charge exchange between H 2 + and Na
1987
The difference in charge exchange rate in collisions between spin oriented sodium atoms and H 2 + ions has been measured at an energy of about 1 eV. H 2 + was stored in a Penning trap and polarized by spin exchange with Na beam atoms from a hexapole magnet. The ion loss from the trap due to charge exchange was different as we depolarized the atomic beam. From the data we obtain a ratio of cross sections for singlet and triplet collisionsQ 1/Q 3=1.5±0.2 andQ 3=1.2·10−15 cm2.
Mössbauer Spectroscopic Evidence of Angle-Dependent Intersystem Crossing in LiNbO3:Fe3+
1986
M\"ossbauer emission spectra of LiNb${\mathrm{O}}_{3}$:$^{57}\mathrm{Co}$ single crystals in magnetic fields up to 5 T at 4.2 K show initial populations of the $^{6}A_{1\mathrm{g}}$ Zeeman substates of ${\mathrm{Fe}}^{3+}$ which depend strongly on the angle between the crystallographic $c$ axis and the magnetic field. This is interpreted in terms of a crystal-field effect on excited states which influences the initial populations of the Zeeman sublevels of the $^{6}A_{1\mathrm{g}}$ ground term after the electron-capture decay of $^{57}\mathrm{Co}$. An intersystem crossing process due to orbit-lattice interaction can fairly well explain the angular dependence.
Inelastic and quasi-elastic light scattering in (NaCN)1?x(KCN)x quadrupolar glasses
1990
The elastic constantsc11 andc44, and the attenuation of longitudinal phonons along (100)-direction in (NaCN)1−x(KCN)x mixed crystals have been determined by brillouin spectroscopy in the temperature range fromT=10K−300K. Minima inc44 (T) which determine the freezing tempratureTF in these orientational glasses appear at lower temperatures compared to neutron scattering results. The coupling of molecular reorientations to longitudinal phonons in NaCN-rich smaples shows up in dispersion effects inc11 (T) and the appearence of a dynamical central peak nearTF.
Line mixing in the stimulated Raman spectrum of the ν1 band of SiH4 at 0.4–1.0 bar
1993
The stimulated Raman spectrum of the ν1 band of SiH4 has been recorded at 0.4 and 1.0 bar pressures and room temperature. Line mixing of the fine structure components of this spectrum was taken into account in a calculated profile by considering coupling between the main transitions and using a simple model (strong collision model, SCM) for the relaxation matrix.