The preparation and physical characterization of two copper(I) complexes Cu(HL)NO₃ and [Cu(HL)₂]NO₃·MeOh formed with a newly synthesized tridentate [S,N,P] HL = 2-(diphenylphosphino)benzaldehyde thiosemicarbazone ligand and the crystal structure analysis of the latter have been carried out. An X-ray study of [Cu(HL)₂]NO₃·MeOH revealed a copper(I) ion coordinated tetrahedrally to S,N,P,P atoms donated by two HL ligands. One is tridentate [S,N,P], whereas the second HL ligand is monodentate, ligating only its phosphorus atom to the copper. The geometry around the four-coordinate Cu(I) is comparable with Cu{N,S,P,X} tetrahedra (X = N, P, or S) retrieved from the Cambridge Structural Database. In addition, with a restriction to Cu{N,P,X,X} (X = C,N,P) tetrahedra ‐ S is excluded ‐ ca. 60 structures against

This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl₂(H₂O)]Cl (1) and [Fe(PLAG)₂](NO₃)₃ (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)₂](NO₃)₃ (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized.