# Steric, Activation Method and Solvent Effects on the Structure of Paddlewheel Diruthenium Complexes
## 3 Results and Discussion
### Magnetic Properties
For the fit of the magnetic data of **1a**, two different paramagnetic impurities have been taken into account: (a) a Ru(III) monomer with S = 1/2 as it is usual in similar fits (see above) and (b) compound **1b**, i.e., a polymorph of compound **1a** forming discrete molecules with the fixed g, D and zJ values obtained in the fit of **1b**. The results of these fits are also shown in Table 4, where the \(\sigma^{2}\) values obtained indicate good agreements between the experimental data and the calculated curves for the two fits. Figures 5 and S4 show, respectively, the experimental and calculated curves considering compound **1b** and a mononuclear Ru(III) as impurity. The calculated zJ values are \(-11.57\) cm\({}^{-1}\) (fit a) and \(-14.11\) cm\({}^{-1}\) (fit b). These values are larger than those obtained for compounds **1b**, **2** and **3** and close to those found in similar diruthenium(II,III) complexes with linear Ru-Cl-Ru angles [23; 49; 50; 51; 52]. This is indicative of stronger antiferromagnetic couplings in linear compounds than in molecular or zigzag complexes. The amount of paramagnetic impurity obtained in fit (a) (2.60%) is similar to those obtained for similar linear complexes [23; 49; 50; 51; 52]. Fit b yields a higher impurity percentage (12.54%) but also \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Compound** & **g** & **D/cm\({}^{-1}\)** & **zJ/cm\({}^{-1}\)** & **TIP/emu mol\({}^{-1}\)** & **P/\%** & \(\sigma^{2}\) \\ \hline
**1a** & 2.00 \({}^{\text{ac}}\) & 59.25 & \(-11.57\) & \(9.83\times 10^{-4}\) & 2.60 & 8.32 \(\times\)\(10^{-5}\) \\
**1b** & 2.21 \({}^{\text{b}}\) & 82.23 & \(-14.11\) & \(3.40\times 10^{-5}\) & 12.54 & 1.30 \(\times\)\(10^{-5}\) \\
**1b** & 2.22 & 67.47 & \(-0.16\) & \(2.76\times 10^{-7}\) & 2.80 & 1.07 \(\times\)\(10^{-4}\) \\
**2** & 2.12 & 59.66 & \(-0.09\) & \(2.24\times 10^{-4}\) & \(2.67\times 10^{-7}\) & 3.24 \(\times\)\(10^{-5}\) \\
3 & 2.02 & 60.31 & \(-0.32\) & \(5.80\times 10^{-3}\) & 0.47 & 4.46 \(\times\)\(10^{-5}\) \\ \hline \hline \end{tabular}  
* Considering a Ru(III) monomer as impurity. \({}^{\text{b}}\) Considering **1b** as impurity. \({}^{\text{c}}\) Fixed parameter.  
\end{table} 
Table 4: Magnetic parameters obtained in the fits of the magnetic moment versus temperature curves for compounds **1**-**3**. Figure 4: Temperature dependence of the molar susceptibility (o) and magnetic moment (\(\Delta\)) for compound [Ru\({}_{2}\)Cl(\(\mu\)-O\({}_{2}\)CC\({}_{6}\)H\({}_{4}\)-oO\(\text{Me}\))\({}_{4}\)(EtOH)] (**1b**). Solid lines are the product of a least-squares fit of the experimental data to the model indicated in the text. a better quality of the fit, considering the higher \(\sigma^{2}\) value. Since the elemental analysis and the UV-Vis-NIR spectrum indicate that compound **1a** is a chemically pure sample, this paramagnetic impurity is likely a fraction of the same compound with molecular arrangement or zigzag chains. The presence of different polymorphs of the same complex as magnetic impurities has been previously postulated for similar tetracarboxylicato [32] and tetraamidatodiruthenium(II,III) [23] complexes. In summary, the maximum in the magnetic susceptibility curve for complex **1a** clearly indicates that this complex has a polymeric linear structure. The absence of this maximum in complexes **2** and **3** and its high insolubility in polar and non polar solvents indicate a polymeric zig-zag chains arrangement [1,2,4].