[CpNi(diselenolene)] Neutral Radical Complexes:  Electron Paramagnetic Resonance and Density Functional Theory Investigations

Abstract

Se-enriched CpNi(bds) (bds ) 1,2-benzenediselenolate), has been synthesized and its g tensor and 77 Se hyperfine tensors have been obtained from its frozen solution electron paramagnetic resonance (EPR) spectrum. These parameters are consistent with those calculated by density functional theory (DFT); it is shown that 10% of the spin is localized on each selenium and that the direction associated to the maximum 77 Se couplings is aligned along the g min direction, perpendicular to the Ni(bds) plane. EPR measurements and DFT calculations are also carried out on the 77 Se enriched complex CpNi(dsit) as well on the two dithiolene analogues CpNi-(bdt) and CpNi(dmit). The optimized structures of the isolated CpNi(bds) and CpNi(bdt) complexes have been used to generate the idealized dimers (bds)NiCp‚‚‚CpNi(bds) and (bdt)NiCp‚‚‚CpNi(bdt) characterized by Cp‚‚‚Cp overlap. The exchange parameters J calculated at the DFT level for these systems are in reasonable accord with the experimental values. The influence of the geometry of the dimer on its magnetic properties is assessed by calculating the variation of J as a function of the relative orientation of the two Ni(diselenolene) or Ni(dithiolene) planes.

Radical CpNi(dithiolene) and CpNi(diselenolene) complexes: Synthetic routes and molecular properties

“…The reactions of Cp 2 Ti and PhSb dithiolene (or diselenolene) complexes with 1-3 (Scheme 7) are summarized in Table 3. We also report here the unpublished reaction of [Cp 2 Ti(diselenolene)] complexes, which was investigated in the search for an efficient preparation of [CpNi(diselenolene)] marked with 77 Se [41]. The reactions of (NR 4 ) 2 [Zn(dithiolene) 2 ] (or diselenolene) are described in Part 2.7.…”

“…They have not been published but we describe them here for the sake of completeness, as they were Scheme 11. [41]. In addition, the 77 Se-enriched [CpNi(bds)] complex has been also synthesized from 2 and (PPh 4 ) 2 [Zn(bds) 2 ] [41] (Scheme 13).…”

“…[41]. In addition, the 77 Se-enriched [CpNi(bds)] complex has been also synthesized from 2 and (PPh 4 ) 2 [Zn(bds) 2 ] [41] (Scheme 13).…”

“…5. Experimental (black) and simulated (red) EPR spectra obtained at 77 K with a THF solution of CpNi(bdt) (a) and CpNi(bds) (b) [41]. Hyperfine interactions, when observable on EPR spectra, can provide a direct information about the spin density distribution, allowing for a rationale of the solid state magnetic properties of these radicals [20,21].…”

Physical Chemistry at the University of Geneva

“…These results combined with those obtained from DFT studies of the dimer [(CpNi(diselenolenes)] 2 led to the rationalisation of the antiferromagnetic properties measured in the crystalline state. [15] In a related context, in collaboration with the group of Dr. N. Avarvari of the University of Angers, the laboratory turned its attention to the electronic structure of molecules containing several tetrathiafulvalene (TTF) fragments. The aim was to demonstrate, with the aid of EPR/ENDOR measurements and cyclic voltammetry, the role of the bridging heteroatoms in the spin delocalisation.…”