Search results for "Partial charge"
showing 6 items of 6 documents
Superexchange-mediated electronic energy transfer in a model dyad
2010
On the basis of time-dependent density functional theory (TD-DFT) calculations coupled to the polarizable continuum model (PCM) and single molecule spectroscopic studies, we provide a detailed investigation of excitation energy transfer within a model bi-chromophoric system where a perylene monoimide (PMI) donor is bridged to a terrylene diimide (TDI) acceptor through a ladder-type pentaphenylene (pPh) spacer. We find that the electronic excitation on the PMI donor significantly extends over the bridge giving rise to a partial charge transfer character and inducing a approximately 3-fold increase in the electronic interaction between the chromophores, which explains the failure of the Först…
Synthesis and Crystal Structure of a Novel Lamellar Barium Derivative: Ba(VOPO4)2·4H2O. Synthetic Pathways for Layered Oxovanadium Phosphate Hydrate…
1997
A unified synthetic strategy has allowed us to rationalize the preparative chemistry of the layered oxovanadium phosphates M(VOPO4)2·nH2O. Thus, we have been able to isolate as single phases with reasonable yields both all the previously characterized phosphates and a new solid containing Ba2+ cations as guest species as well as to prepare new related derivatives involving arsenate anions. In order to organize the experimental results, we have used two complementary models: a simple restatement of the partial charge model (PCM), and the valence matching principle (VMP) (derived from the bond valence method). The crystal structure of the new barium lamellar derivative, Ba(VOPO4)2·4H2O, has …
Synthetic Pathways for New Tubular Transition Metal Hydroxo- and Fluoro-Selenites: Crystal Structures ofM12(X)2(SeO3)8(OH)6(M=Co2+,Ni2+;X= OH−)
1996
The dumortierite-family structuresM12X2(SeO3)8(OH)6(M= Co2+and Ni2+;X= OH−and F−) have been synthesized. The crystal structures of the hydroxo-derivatives have been refined from X?ray powder diffraction data in the space groupP63mc(Z= 1) witha= 12.887(3) A andc= 4.981(4) A (M= Co2+,X= OH−or F−) anda= 12.704(5) A andc= 4.925(6) A (M= Ni2+,X= OH−or F−). Application of the Partial Charge Transference Model allows the understanding of the selenite derivatives crystal chemistry.
Orbital-Resolved Partial Charge Transfer from the Methoxy Groups of Substituted Pyrenes in Complexes with Tetracyanoquinodimethane—A NEXAFS Study
2012
It is demonstrated that the near-edge X-ray absorption fine structure (NEXAFS) provides a powerful local probe of functional groups in novel charge transfer (CT) compounds and their electronic properties. Microcrystals of tetra-/hexamethoxypyrene as donors with the strong acceptor tetracyano-p-quinodimethane (TMP/HMP-TCNQ) were grown by vapor diffusion. The oxygen and nitrogen K-edge spectra are spectroscopic fingerprints of the functional groups in the donor and acceptor moieties, respectively. The orbital selectivity of the NEXAFS pre-edge resonances allows us to precisely elucidate the participation of specific orbitals in the charge transfer process. Upon complex formation, the intensit…
Silicon Oxysulfide, OSiS: Rotational Spectrum, Quantum-Chemical Calculations, and Equilibrium Structure.
2011
Silicon oxysulfide, OSiS, and seven of its minor isotopic species have been characterized for the first time in the gas phase at high spectral resolution by means of Fourier transform microwave spectroscopy. The equilibrium structure of OSiS has been determined from the experimental data using calculated vibration-rotation interaction constants. The structural parameters (rO-Si = 1.5064 A and rSi-S = 1.9133 A) are in very good agreement with values from high-level quantum chemical calculations using coupled-cluster techniques together with sophisticated additivity and extrapolation schemes. The bond distances in OSiS are very short in comparison with those in SiO and SiS. This unexpected fi…
Complexes of organometallic compounds. L. The correlation between 119Sn mössbauer isomer shifts and calculated partial charges on tin in adducts of t…
1981
Abstract The relationship between Mossbauer isomer shifts, δ, and atomic charges on tin, QSn has been studied for homologous series RnSnhal4−n· L2 [ n = 0−3; L2 = donor atoms of 1, 2-bis(dipheylphosphino)ethane, N, N′-ethylenebes(salicylideneimine) and N, N′-ethylenbes(acetylacetoneimine)] and Snhal4· 2PR3. Semiempirical values of QSn have been calculated by two methods based on the concept of orbital electronegativity equalization upon bond formation. Linear correlations δ/QSn are obtained, which can be function of the coordination number of the metal atom, for terms of the series characterized by different orbital electronegativities of atoms directly bound to tin. Deviations occur for ad…