Role of the Coordination of the Azido Bridge in the Magnetic Coupling of Copper(II) Binuclear Complexes

Abstract

It is well-known that the azido bridge gives rise antiferromagnetic (AF) or ferromagnetic (F) coupling depending on its coordination mode, namely end-to-end or end-on, respectively. The aim of the present work is to analyse the factors contributing to this different magnetic behaviour. The difference dedicated configuration interaction (DDCI) method is applied to several binuclear Cu(II) azido-bridged models with both types of coordination. In end-on complexes, the direct exchange and the spin polarisation contributions are found to be responsible for the ferromagnetic coupling. In end-to-end complexes, both the direct exchange and the spin polarisation are small and the leading term is the antiferromagnetic dynamical polarisation contribution. The most relevant physical effects are included in the DDCI calculations so that good quantitative agreement is reached for the coupling constant as well as the spin densities.

Analysis of the magnetic coupling in binuclear systems. III. The role of the ligand to metal charge transfer excitations revisited

“…Many calculations have shown the performance of DDCI estimates of the magnetic coupling. [20][21][22][23][24][25][26][27][28][29][30][31][32] The results reported in Table I show that the J values obtained at CAS+ S and DDCI2 levels are far from experimental ones, which suggest that an important part of the effects is missed. It is therefore concluded that 2h-1p and 1h-2p configurations bring from 30% to 50% of magnetic coupling.…”

“…So far, the DDCI approach has been extensively employed in the evaluation of J in molecular and solid state magnetic materials with a remarkable good agreement with experiment. [20][21][22][23][24][25][26][27][28][29][30][31][32] Some years ago we took benefit of this methodology to analyze in depth the physical contributions to the magnetic coupling on a series of binuclear Cu ͑II͒ complexes. 33 The use of the DDCI strategy allows not only to obtain quite accurate J values but also to analyze the various physical effects by generating CI spaces of increasing lengths that include different types of determinants.…”

Singlet-triplet gaps in large multireference systems: Spin-flip-driven alternatives for bioinorganic modeling

“…Indeed, some purely ab initio approaches have already tackled that problem. [100][101][102][103][104][105][106] In this section, we will illustrate how SF-DFT computations can help in designing such a space. The starting idea is very simple: as SF-DFT computations are not the limiting CPU-time step if aiming at performing a pure high-level ab initio multireference correlated computation, then, let us first perform a SF-DFT computation and retain in the zeroth-order space to be built only those electrons and orbitals involved in the final SF-DFT wave functions.…”

Ferromagnetic Interaction in an Asymmetric End‐to‐End Azido Double‐Bridged Copper(II) Dinuclear Complex: A Combined Structure, Magnetic, Polarized Neutron Diffraction and Theoretical Study

“…As evidenced from Table 1, several structural parameters have to be considered: not only the coordination geometry, [34] but also the CuÀN bond lengths or the Cu-N-N-Cu torsion angle, as recently pointed out. [11,23] Obviously, the azido bridge is non-innocent in the exchange process [29] Therefore, even weak ferromagnetic coupling in EE systems still deserves attention.…”