Pulsed EPR and ab initio calculation on [Ni(CN)(4)](3-) in NaCl and KCl host lattices

Paramagnetic 3d(9) [Ni(CN)(4)](3-) complexes, with the unpaired electron in a d(x2-y2) orbital, have been generated from diamagnetic Ni(II) 3d(8) cyan ide complexes in KCl or NaCl host lattices. The magnetic and quadrupolar hy perfine interactions with the four N-14, hidden in the CW-EPR (continuous w ave electron paramagnetic ressonance) line width, are revealed by pulsed EP R 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 orbita l assignment and are in agreement with the measured hyperfine values. The t rend of N-14 A(iso) values (7.7 MHz for NaCl and 6.8 MHz for KCI) is given by the Ni-CN distance, modified in each host lattice. Small asymmetry facto rs (about 0.04) for the N-14 quadrupolar tensor are obtained both in experi ment and in theory. The experimental lines and the calculations indicate sp in density at the cations of both lattices. Experimental and theoretical da ta indicate that lattice chlorine ions near the Ni atom, in axial positions , are not chemically coordinated to Ni. Spin density on these ions arises o nly from spin polarization of their valence orbitals and of the valence orb itals of the complex.