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Strong Magnetic Interactions through Weak Bonding Interactions in Organometallic Radicals: Combined Experimental and Theoretical Study
Author(s) -
Cauchy Thomas,
Ruiz Eliseo,
Jeannin Olivier,
Nomura Mitsushiro,
Fourmigué Marc
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200700081
Subject(s) - chemistry , delocalized electron , stacking , antiferromagnetism , density functional theory , intermolecular force , crystallography , radical , moiety , computational chemistry , stereochemistry , condensed matter physics , molecule , organic chemistry , physics
The magnetic properties of a series of three neutral radical organometallic complexes of general formula [CpNi(dithiolene)] . have been investigated by a combination of X‐ray crystal structure analysis and magnetic susceptibility measurements, while the assignment of the exchange coupling constants to the possible exchange pathways has been accomplished with the help of calculations based on density functional theory (DFT). The syntheses and X‐ray structures of [CpNi(adt)] (adt=acrylonitrile‐2,3‐dithiolate) and [CpNi(tfd)] (tfd=1,2‐bis(trifluoromethyl)ethene‐1,2‐dithiolate) complexes are described, while [CpNi(mnt)] (mnt=maleonitriledithiolate) was reported earlier. In the three complexes, we observed strong antiferromagnetic coupling that could not be explained solely by short S⋅⋅⋅S intermolecular contacts. Our calculations indicated that spin density in these complexes is strongly delocalized on the NiS 2 moiety, with up to 20 % on the Cp ring. As a consequence, Cp⋅⋅⋅Cp and Cp⋅⋅⋅dithiolene overlap interactions have been identified as responsible for antiferromagnetic couplings. The [CpNi(adt)] complex thus has a value J =−369.5 cm −1 for an exchange interaction through a π stacking due to the Cp⋅⋅⋅Cp overlap.