2013-05-24 14:30:27 956 Mishra, Vibha Mukherjee, Rabindranath Linares, Jorge Codjovi, Epiphane Varret, François Lawson Daku, Latévi Max Hyperfine Interactions Hyperfine Interactions 0304-3843 2009 188 1-3 71 78 H 57Fe Mössbauer spectroscopy ; iron(II) complex ; ligand-field ; density functional theory ]]> spin-transition ⁵⁷Fe Mössbauer spectroscopy iron(II) complex ligand-field density functional theory http://www.springerlink.com/content/v0403r0210877pj1/ http://www.springerlink.com/content/v0403r0210877pj1/fulltext.pdf The spin-transition (¹A₁↔⁵T₂) behaviour of a new mononuclear iron(II) compound [Fe^II(L)₃][PF₆]₂[L = 2-[3-(2′-pyridyl)pyrazole-1-ylmethyl]pyridine] has been investigated by ⁵⁷Fe Mössbauer spectroscopy. Analysis of the Mössbauer spectra revealed low value of the quadrupole splitting of the high-spin state which reflects iron(II) to be in nearly cubic lattice site. Mössbauer spectra under light show the light-induced excited spin state trapping effect and the observed quadrupole splitting of the metastable high-spin state is found little sensitive to the high-spin fraction value. DFT calculations are in progress to document the almost cubic nature of the ligand-field acting on the iron atom.

]]> H150I299P390 10.1007/s10751-008-9891-6 3560 http://www.unige.ch/sciences/chifi/publis/pics/double/ref00956.png http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref00956.pdf 957 Matthew D. Wodrich, Alfredo Vargas, Pierre-Yves Morgantini, Gabriel Merino, Clémence Corminboeuf Wodrich, Matthew D. Vargas, Alfredo Morgantini, Pierre-Yves Merino, Gabriel Corminboeuf, Clémence Journal of Physical Organic Chemistry J. Phys. Org. Chem. 0894-3230 2008 22 2 101 109 H stereoelectronic effects • electron delocalization • hyperconjugation • density functional theory stereoelectronic effects electron delocalization hyperconjugation density functional theory http://www3.interscience.wiley.com/journal/121384175/abstract http://www3.interscience.wiley.com/cgi-bin/fulltext/121384175/PDFSTART The trigonal planar geometry of the nitrogen atom in commonly used phosphoramidite ligands is not in line with the traditional valence shell electron pair repulsion (VSEPR) model. In this work, the effects governing nitrogen configuration in several substituted aminophosphines, A₂PNB₂ (A or B = H, F, Cl, Br, Me, OMe, BINOP), are examined using modern computational analytic tools. The electron delocalization descriptions provided by both electron localization function (ELF) and block localized wavefunction analysis support the proposed relationships between conformation and negative hyperconjugative interactions. In the parent H₂PNH₂, the pyramidal nitrogen configuration results from nitrogen lone pair electron donation into the σ* P — H orbital. While enhanced effects are seen for F₂PNMe₂, placing highly electronegative fluorine substituents on nitrogen (i.e., Me₂PNF₂) eliminates delocalization of the nitrogen lone pair. Understanding and quantifying these effects can lead to greater flexibility in designing new catalysts.

]]> P903 10.1002/poc.1431 3181 http://www.unige.ch/sciences/chifi/publis/refs_pdf/ref00957.pdf