Synthesis and characterization of tetraphenylporphyrin manganese(III) complexes of phenylcyanamide ligands

Several complexes of TPPMn–L, where TPP is the dianion of tetraphenylporphyrin and L is monoanion of 4-methylphenylcyanamide (4-Mepcyd) (1), 2,4-dimethylphenylcyanamide (2,4-Me2pcyd) (2), 3,5-dimethylphenylcyanamide (3,5-Me2pcyd) (3), 4-methoxyphenylcyanamide (4-MeOpcyd) (4), phenylcyanamide (pcyd) (5), 2-chlorophenylcyanamide (2-Clpcyd) (6), 2,5-dichlorophenylcyanamide (2,5-Cl2pcyd) (7), 2,6-dichlorophenylcyanamide (2,6-Cl2pcyd) (8), 4-bromophenylcyanamide (4-Brpcyd) (9), and 2,3,4,5-tetrachlorophenylcyanamide (2,3,4,5-Cl4pcyd) (10), have been prepared from the reaction of TPPMnCl and thallium salt of related phenylcyanamide. Each of the complexes has been characterized by IR, UV–Vis and 1H NMR spectroscopies.4-Methylphenylcyanamidotetraphenylporphyrin manganese(III) crystallized with one molecule of solvent CHCl3 in the triclinic crystal system and space group P1¯ with the following unit cell parameters of: a = 11.596(6) Å; b = 11.768(9) Å; c = 17.81(2) Å; and α, β, γ are 88.91(9)°, 88.16(7)°, 67.90(5)°, respectively; V = 2251(3) Å3; Z = 2. A total of 4234 reflections with I > 2σ(I) were used to refine the structure to R = 0.0680 and Rw = 0.2297. The Mn(III) shows slightly distorted square pyramidal coordination with the 4-methylphenylcyanamide in the axial position, coordinated from nitrile nitrogen. The reduction of each of the TPPMn–L complexes was also examined in dichloromethane and spectroelectrochemical behavior of (1) was investigated and compared to TPPMnCl.

Graphical abstractTen complexes of TPPMn–L (TPP = dianion of tetraphenylporphyrin and L = monoanion of phenylcyanamides) have been prepared and characterized by IR, UV–Vis and 1H NMR spectroscopies. Structure of TPPMn(4-Mepcyd) was studied by X-ray crystallography. Coordination of phenylcyanamide ligand to both Mn(II) and Mn(III) was confirmed with spectroelectrochemical method.Figure optionsDownload full-size imageDownload as PowerPoint slide