EPR AND ENDOR SPECTRA OF COPPER(II) CENTERS WITH D22 AND DX2-Y2 GROUND-STATES IN BA2ZNF6 - ANALYSIS OF HYPERFINE PARAMETERS AND DYNAMIC VIBRONIC COUPLING

被引:50
作者
STEFFEN, G
REINEN, D
STRATEMEIER, H
RILEY, MJ
HITCHMAN, MA
MATTHIES, HE
RECKER, K
WALLRAFEN, F
NIKLAS, JR
机构
[1] UNIV MARBURG,FACHBEREICH CHEM,W-3550 MARBURG,GERMANY
[2] UNIV BONN,INST MINERAL PETR,W-5300 BONN,GERMANY
[3] UNIV TASMANIA,DEPT CHEM,HOBART,TAS 7001,AUSTRALIA
[4] UNIV GESAMTHSCH PADERBORN,FACHBEREICH PHYS,W-4790 PADERBORN,GERMANY
关键词
D O I
10.1021/ic00336a018
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Ba2ZnF6 is one of the few host lattices in which Cu2+ can be stabilized with a dz2 ground state by isomorphous substitution of Zn2+ (center I). Cu2+ is forced to adopt a strongly tetragonally compressed octahedral coordination in this case due to the strain of the ZnF6 host polyhedra, which are slightly distorted in the same way. EPR and ENDOR investigations, which were performed on Cu2+-doped single crystals grown by the Bridgman technique, revealed the presence of a second center (II) with a dx2-y2 ground state (g|| = 2.432, g⊥= 2.076). Center II was identified as Cu2+ on an interstitial site with a quare-planar F− coordination, which is otherwise only known for Cu2+ in CaCuF4. The temperature-dependent g as well as copper and fluoride hyperfine parameters of center I (4.2 K: g|| = 1.992, g⊥ = 2.367) are interpreted in terms of a slight admixture of dx2-y2 caused by vibronic coupling, which increases with temperature. The ground-state potential surface, the vibronic wave functions, and the corresponding energy levels have been numerically calculated. The transferred spin densities of the two centers, derived from the ligand hyperfine structure at 4.2 K (25 ± 2%) are comparable to those of Cu2+-doped K2ZnF4 (dz2 ground state). The mixing coefficients for the dx2-y2 and dz2 orbitals in the ground state MO's of the three centers are practically identical (α = 0.92). © 1990, American Chemical Society. All rights reserved.
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页码:2123 / 2131
页数:9
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