Pulsed EPR and Ab Initio Calculation on [Ni(CN)4]3- in NaCl and KCl Host Lattices

Abstract

Paramagnetic 3d9 [Ni(CN)4]3- complexes, with the unpaired electron in a dx2−y2 orbital, have been generated from diamagnetic Ni(II) 3d8 cyanide complexes in KCl or NaCl host lattices. The magnetic and quadrupolar hyperfine interactions with the four 14N, hidden in the CW-EPR (continuous wave electron paramagnetic ressonance) line width, are revealed by pulsed EPR and ENDOR (electron nuclear double resonance) angular variation studies. Ab initio embedded UMP2 cluster calculations, which take into account short- and long-range crystal interactions, confirm the unpaired electron orbital assignment and are in agreement with the measured hyperfine values. The trend of 14N Aiso values (7.7 MHz for NaCl and 6.8 MHz for KCl) is given by the Ni−CN distance, modified in each host lattice. Small asymmetry factors (about 0.04) for the 14N quadrupolar tensor are obtained both in experiment and in theory. The experimental lines and the calculations indicate spin density at the cations of both lattices. Experimental and...