**2. Results and Discussion**

The reaction between Fe(NO3)3·9H2O and the pro-ligand *N*--acetylpyrazine-2-carbohydrazide (H2L) in methanol results in the formation of the mononuclear Fe(III) complex [Fe(HL)(NO3)(H2O)2]NO3 (**1**) (Scheme 1). Complexes **2** and **3** were synthesized according to the literature [45]. These complexes were characterized by elemental analysis, infrared (IR) spectroscopy, and electrospray ionization mass spectrometry (ESI-MS) and, for **1**, also by X-ray single crystal di ffraction analysis. The expected characteristic stretching bands of HL− in **1** are shifted to lower wavenumbers relative to those in the pro-ligand (see the experimental section), specifically the ν(NH) at 3136 cm<sup>−</sup><sup>1</sup> and the <sup>ν</sup>(C=O) detected at 1678 and 1646 cm<sup>−</sup>1; the band for nitrate ions occurs at the typical value of 1383 cm<sup>−</sup><sup>1</sup> [51]. The molecular ion was not observed in the ESI-MS analysis (see the experimental section), but instead, the species [M-(NO3)]+ resulting from the loss of the nitrate counter-ion was detected.

**Scheme 1.** Syntheses of **1**–**3**.
