Nonempirical valence bond studies of the origin of the antiferromagnetism of copper(II) carboxylate dimers

Abstract

Figure 1. Potential energy diagramme for CH3N2+ isomers. Relative energies (referred to the energy of H2NCH2+ (J)) are given in kcal/mol.The reaction co-ordinate is a complex co-ordinate. transition state of singlet diradicaloid character. As the UHF method (which has been used to localize this saddle point) is known for its poor description of singlet diradicals, the energy of TS14 is likely to be too high. But, ion 6 also seems to be prevented by significant barriers from spontaneous dissociation. In Figure 1 the various isomerization/dissociation processes are given in a simplified two-dimensional potential energy surface.Heats of formation AH0, of 5 and 6 can be estimated from combining the AH0, of reactions 1-5 with the experimentally determined heats of formation of the various mono-cations;14 by doing this, for H2NCH2+ (5) an averaged value of AH°= 644 kcal/mol and for H3NC2+ (6) of AH°= 700 kcal/mol is obtained.Both numbers indicate the extreme thermodynamic instability of the two dications, and it is highly unlikely to ever generate a stable CH3N2+ species in solution. Proton transfer to the solvent shell or capture of negatively charged species from it will occur with avidity.Acknowledgment. The financial support of our work by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie is gratefully acknowledged. We are particularly indebted to the Computer Centres of TU Berlin and the Konrad-Zuse-Zentrum Berlin for generously providing computer time.

Electrochemical Synthesis and Structural Characterization of a Novel Mixed-valence Copper (I)-copper (II) Complex: {[Bis(ethylenediamine) Copper (II)] Bis[diiodocuprate (I)]}

“…Although to date remarkable Cu(I) complexes [8][9][10][11] and examples of Cu(I) complexes with halocuprate anion [12][13][14] have been reported, there is no report on diiodocuprate (I) anion polymeric complex with ethylenediamine. Thus, we report herein the electrosynthesis and crystal structure of a novel Cu(I) polymeric complex with potentiostatic dissolution of copper anode in a solution of ethylendiamine and iodine in AcN.…”

Modeling of Copper(II) Complexes with the SIBFA Polarizable Molecular Mechanics Procedure. Application to a New Class of HIV-1 Protease Inhibitors

“…The Cu 2+ acetate complexation has been previously reported. In the solid state, the Cu 2+ acetate monohydrate is observed as a dimer with the general formula [Cu(OAc) 2 (H 2 O)] 2 : the two Cu 2+ are bridged symmetrically by the four acetate ligands, with the two copper ions antiferromagnetically coupled . In solution, a dissociation mechanism occurs leading to the mononuclear form of the complex .…”

Synthesis, crystal structure and properties of [Cu2(O2CC6H4Me-p)3(Me2NCH2CH2NMe2)2]PF6: an unprecedented [Cu2(μ-O2CR)4] into [Cu2(μ-O2CR)3]+ core conversion †

“…11, 12 As the superexchange interaction is operative through the carboxylate bridge, the magnitude of antiferromagnetic interaction (Ϫ2J) is expected to be dependent on the number of bridging carboxylate ligands. 24 Complex 1 with m = 3 is expected to have a Ϫ2J value between those having m = 4 and 2 (Table 2). Instead, the Ϫ2J value of 81.4 cm Ϫ1 in 1 is close to the range observed for the dibridged core.…”