Iron(III) complexes with tridentate Schiff bases derived from diaminomaleonitrile: Synthesis and characterization

Schiff bases are compounds having an imine group, R1R2C=NR, which are formed by the condensation of a primary amine with a compound bearing a carbonyl group1. The understanding that the ligands coordinated with metals in natural systems are asymmetrical has aroused interest in the synthesis and characterization of asymmetric Schiff bases derived from amines suitable to form complexes with transition metals2. In this work, iron(III) complexes with tridentate Schiff bases derived diaminomaleonitrile (Figure 1) were synthesized by adaptation of published method3. The complex (1) was soluble in THF, methanol, ethanol and acetonitrile, being partially soluble in water and insoluble in hexane. Complex (2) was soluble in methanol and ethanol, partially soluble in water, THF and acetonitrile, and insoluble in hexane. The general characterization data are found in Table 1. Both complexes degraded instead of melting. The conductivity measurements, carried out in methanol, indicate the complexes as 1:1 electrolytes, possibly due to the exchange of a Cl- ligand by a solvent molecule. The electronic spectra, performed with methanolic solutions, presented three bands of high molar absorptivity, between 270 nm and 400 nm, attributed to the transitions  e n  *. Also, bands of low molar absorptivity, referring to the d-d transitions observed in 750 nm for complex (1) and 760 nm for complex (2). Vibrational Spectra and Elemental Analyses will be performed to corroborate the structures proposed and will be presented at 41st RASBQ.