Discrepancy between the spin distribution and the magnetic ground state for a triaminoxyl substituted triphenylphosphine oxide derivative

被引:14
作者
Borobia, OB
Guionneau, P
Heise, H
Köhler, FH
Ducasse, L
Vidal-Gancedo, J
Veciana, J
Golhen, S
Ouahab, L
Sutter, JP [1 ]
机构
[1] Tech Univ Munich, Inst Anorgan Chem, D-85747 Garching, Germany
[2] Univ Bordeaux 1, Lab Physicochim Mol, F-33405 Talence, France
[3] Inst Ciencia Mat Barcelona, Cerdanyola Del Valles 08913, Spain
[4] Univ Rennes 1, CNRS, LCSIM, UMR 6511,InstChim Rennes, F-35042 Rennes, France
[5] Max Planck Inst Biophys Chem, D-37077 Gottingen, Germany
[6] Univ Bordeaux 1, CNRS, Inst Chim Mat Condensee Bordeaux, F-33608 Pessac, France
关键词
EPR spectroscopy; magnetic properties; NMR spectroscopy; radicals; spin distribution;
D O I
10.1002/chem.200400656
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The magnetic interaction and spin transfer via phosphorus have been investigated for the tri-tert-butylaminoxyl para-substituted triphenylphosphine oxide. For this radical unit, the conjugation existing between the pi* orbital of the NO group and the phenyl pi orbitals leads to an efficient delocalization of the spin from the radical to the neighboring aromatic ring. This has been confirmed by using fluid solution high-resolution EPR and solid state MAS NMR spectroscopy. The spin densities located on the atoms of the molecule could be probed since H-1, C-13, N-14, and P-31 are nuclei active in NMR and EPR, and lead to a precise spin distribution map for the triradical. The experimental investigations were completed by a DFT computational study. These techniques established in particular that spin density is located at the phosphorus (p=-15 x 10(-3) au), that its sign is in line with the sign alternation principle and that its magnitude is in the order of that found on the aromatic C atoms of the molecule. Surprisingly, whereas the spin distribution scheme supports ferromagnetic interactions among the radical units, the magnetic behavior found for this molecule revealed a low-spin ground state characterized by an intramolecular exchange parameter of J = -7.55 cm(-1) as revealed by solid state susceptibility studies and low temperature EPR. The X-ray crystal structures solved at 293 and 30 K show the occurrence of a crystallographic transition resulting in an ordering of the molecular units at low temperature.
引用
收藏
页码:128 / 139
页数:12
相关论文
共 56 条
[1]  
[Anonymous], 1995, ANGEW CHEM, V107, P973
[2]  
ATHERTON NM, 1993, PRINCIPLE ELECT SPAI
[3]   HIGH-TEMPERATURE SERIES EXPANSIONS FOR SPIN-1-2 HEISENBERG MODEL BY METHOD OF IRREDUCIBLE REPRESENTATIONS OF SYMMETRIC GROUP [J].
BAKER, GA ;
RUSHBROOKE, GS ;
GILBERT, HE .
PHYSICAL REVIEW, 1964, 135 (5A) :1272-+
[4]   Spin-density maps for an oxamido-bridged Mn(II)Cu(II) binuclear compound. Polarized neutron diffraction and theoretical studies [J].
Baron, V ;
Gillon, B ;
Plantevin, O ;
Cousson, A ;
Mathoniere, C ;
Kahn, O ;
Grand, A ;
Ohrstrom, L ;
Delley, B .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1996, 118 (47) :11822-11830
[5]   EFFECTS OF ELECTRON REPULSION IN CONJUGATED HYDROCARBON DIRADICALS [J].
BORDEN, WT ;
DAVIDSON, ER .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1977, 99 (14) :4587-4594
[6]   Ab initio and density functional theory calculations on heteroatom analogues of trimethylenemethane radical ions. Can a quartet be the dground state? [J].
Brown, EC ;
Borden, WT .
JOURNAL OF PHYSICAL CHEMISTRY A, 2002, 106 (12) :2963-2969
[7]   Metal-ligand delocalization in magnetic orbitals of binuclear complexes [J].
Cabrero, J ;
Calzado, CJ ;
Maynau, D ;
Caballol, R ;
Malrieu, JP .
JOURNAL OF PHYSICAL CHEMISTRY A, 2002, 106 (35) :8146-8155
[8]   Spin density distribution of a-nitronyl aminoxyl radicals from experimental and ab initio calculated ESR isotropic hyperfine coupling constants [J].
Cirujeda, J ;
Vidal-Gancedo, J ;
Jürgens, O ;
Mota, F ;
Novoa, JJ ;
Rovira, C ;
Veciana, J .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 2000, 122 (46) :11393-11405
[9]   Triangular antiferromagnets [J].
Collins, MF ;
Petrenko, OA .
CANADIAN JOURNAL OF PHYSICS, 1997, 75 (09) :605-655
[10]   PROTECTION OF HYDROXYL GROUPS AS TERT-BUTYLDIMETHYLSILYL DERIVATIVES [J].
COREY, EJ ;
VENKATESWARLU, A .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1972, 94 (17) :6190-+