## 2 Results and Discussion
### Magnetic Properties  
Since no cooperative magnetism was expected for the mononuclear complexes **I** and **II**, magnetic properties were only investigated for polymeric complexes **III** and **IV**. Electron Paramagnetic Resonance (EPR) spectroscopy at X-band was used to determine the Lande \(g\)-factors that were thereafter used for a quantitative analysis of the magnetic properties. Room temperature X-band EPR spectra from powdered samples of **III** and **IV** are shown in Figure 7. The spectra consist of broad derivative-like signals with widths of \(\Delta H_{pp}\) = 350 and 245 G for **III** and **IV**, respectively. Both complexes are characterized by a \(g\) value of 2.13. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Complex**} & \(d\)**(Cu\({}^{\cdots}\)Cu)** & \(\angle\)**(Cu\({}^{-}\)N\({}^{-}\)N\({}^{-}\)Cu)**\({}^{a}\)** & & \(J\) & \(P\) & \(\chi_{\rm IIP}\times 10^{6}\) & \(zJ^{\prime}/kB\) & \multirow{2}{*}{**Ref. **} \\  & **(Å)** & & (\({}^{\circ}\)) & & & **(cm\({}^{-1}\))** & **(\%)** & **(cm\({}^{3}\) mol\({}^{-1}\))** & **(cm\({}^{-1}\))** & \\ \hline
[Cu(\(\mu_{2}\)-Htrz)(\(\mu_{2}\)-Cl)\({}_{2}\)] & 3.405 & –4.67 & 2.013 & –12.4 & - & - & - & [26, 32] \\
[Cu(\(\mu_{2}\)-NH\({}_{2}\)trz) & 3.4895(5), & –5.8(3), 8.2(4) & 2.26 & –20.4 & - & - & - & [10, 32] \\
[(\(\mu_{2}\)-Cl)\({}_{2}\)] & 3.5210(5) & & & & & & & \\
[Cu(\(\mu_{2}\)-NH\({}_{2}\)trz)\({}_{2}\)Cl] & 3.653(2) & 5.2(3), 11.7(2) & 2.13 & –128.4 & 0.65 & 390 & 11(5) & This \\ Cl:H\({}_{2}\)O **(III)** & & & & & & & & work \\
[Cu(\(\mu_{2}\)-NH\({}_{2}\)trz)\({}_{2}\)Cl] & 3.599(2), & –1.5(5), –13.9(4); & 2.13 & –143.0 & 1.02 & 270 & 80(4) & This \\
[SiFeO\({}_{0.5}\).1.5H\({}_{2}\)O **(IV)** & 3.611(2) & –0.6(5), 11.5(4) & 2.13 & –139.9 & 0.90 & 350 & 0 & work \\
[Cu(\(\mu_{2}\)-NH\({}_{2}\)trz)\({}_{2}\)] & 3.5035(8) & –7.8(4), –13.0(4) & 2.22(1) & –17.7 & - & - & - & [11] \\
[(\(\mu_{2}\)-N\({}_{2}\)-\(N\),\(N\))]NO\({}_{3}\) & & & & & & & & \\
[Cu(\(\mu_{2}\)-NH\({}_{2}\)trz)\({}_{2}\)] & 3.470(2) & 1.5(6), 2.0(5) & 2.21 & –51 & - & - & - & [12] \\ (\(\mu_{2}\)-NCS-\(N\))] & & & & & & & & & \\ ClO\({}_{4}\):0.5H\({}_{2}\)O & & & & & & & & & \\
[Cu(\(\mu_{2}\)-NH\({}_{2}\)trz)\({}_{2}\)] & 3.5301(5) & –11.4(3), –13.8(3) & 2.12 & –75.1 & - & - & –1.1 & [11] \\
[(\(\mu_{2}\)-NO\({}_{3}\))]NO\({}_{3}\) & & & & & & & & \\
[Cu(\(\mu_{2}\)-hyetrz)\({}_{3}\)] & 3.829(2), & –6.4(7), –10.7(9), –37.5(7); &  
**Figure 5.** Thermal ellipsoid (50%) plot of **IV** along the \(a\) (**top**) and \(b\) (**bottom**) axes. The nitrogen atoms are depicted in blue, the carbon atoms in grey, the fluoride atoms in light green, the chloride ions in green, the copper atoms in red, the silicium atoms in yellow and the oxygen atoms are depicted in red. H-atoms were omitted for clarity. **Figure 6.** Thermal ellipsoid (50%) plot of the 1D polymeric chain formed by the \(\{[\rm Cl(H_{2}O)]^{-}\}_{n}\) cluster in the structure of **III**. **Figure 7.** Room temperature X-band EPR spectra from powdered samples of **III** and **IV**. **Figure 8.** The \(\chi_{M}T\) values are 0.40 and 0.39 cm\({}^{3}\) mol\({}^{-1}\) K for **III** and **IV**, respectively, comparable with that expected for one Cu(II) ion (\(S=1/2\)). The temperature profiles of the magnetic susceptibility for both complexes arevery similar. As the temperature decreases, \(\chi_{M}\) increases smoothly reaching a rather broad maximum at ca. 125 K for **III** and ca. 130 K for **IV**. Below these temperatures, \(\chi_{M}\) decreases going through a minimum at ca. 25-30 K before increasing again abruptly (Figure 8). **Figure 8.** Temperature dependence of molar susceptibility \(\chi_{M}\) for powdered samples of **III** and **IV** at 0.1 T. Red solid lines are simulations based on the fitting procedure as discussed in the text. For **IV** the blue line corresponds to the fit obtained assuming \(zJ=0\).