A computational study of structural and magnetic properties of bi- and trinuclear Cu(II) complexes with extremely long Cu---Cu distances
Abstract: Three recently synthesized copper(II) complexes with aroylhydrazones of trifluoroacetic and benzenecarboxylic acids (Dalton Trans., 2013, 42, 16878) have been computationally investigated by densit ...
Summary (1 min read)
3.1. QTAIM analysis for complexes 1-3.
- This fact is in a qualitative agreement with the thermal analysis (TGA) data  that indicate high thermal stability of the complexes up to 250 °C.
- The Py-Cu bonds are comparatively weaker than the other Cu-O and Cu-N bonds (Table 1 ), and therefore an increase of temperature before 250 °C leads to the removal of the pyridine molecules.
3.1. Magnetic properties of the dinucler complexes 1 and 2.
- As can be seen from Figure 2 both complexes 1 and 2 formally are isomeric except the additional axially-coordinated pyridine ligand in complex 2. The distance between the Cu(II) ions for complexes 1 and 2 equals 9.56 and 10.94 Å as determined by X-ray crystallography studies  .
- In order to explain the mechanism of exchange interactions for the studied dicuclear complexes the authors have constructed spin densities and magnetic SOMOs plots with a subsequent analysis of SOMOs decomposition coefficients.
- A detailed analysis of the decomposition coefficients clearly shows that both SOMOs for each complex have non-zero coefficients on the common atoms of the linker moiety.
- In the case of complex 1 the magnetic orbitals are mutually rotated about 120° relative to the inner linker moiety, that means they are side-to-side overlapping in contrast to complex 2 for which head-to-head overlapping occurs.
- The latter case is more spatially preferable and therefore J CuCu for complex 2 is two times higher than for complex 1 despite its longer Cu---Cu distance (10.94 Å vs. 9.56 for complex 1).
3.2. Magnetic properties of the trinuclear complex 3
- Actually, the more accurately the authors can account for the long-range exchange interactions the more reliable agreement with experiment is achieved.
- In their recent publication  the authors have shown that OSS and triplet states of weakly coupled dinuclear Cu(II) complexes become strictly degenerate if they exclude empirical dispersion corrections from their computational scheme.
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Cites background from "A computational study of structural..."
...Even at high gain we were unable to record half-field transitions [26,27], which points to a relatively high (> 10Å) distance between neighboring copper-copper ions....
Cites methods from "A computational study of structural..."
...We have also used a larger basis set for the calculation (6-311+G**) of the magnetic coupling constants [35,36], however the agreement of the theoretical J values with the experimental ones was slightly worse....
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Q1. What are the contributions mentioned in the paper "A computational study of structural and magnetic properties of bi- and trinuclear cu(ii) complexes with extremely long cu---cu distances" ?
The calculated values of spinspin exchange for the studied dinuclear complexes indicate a very weak ferromagnetic coupling of the unpaired electrons in good agreement with experimental data. At the same time, the trinuclear copper ( II ) complex possesses a low-spin doublet ground state with one ferromagnetic and two antiferromagnetic spin projections between the triangular-positioned Cu ions.