Field‐Induced Slow Magnetic Relaxation in a Mononuclear Manganese(III)–Porphyrin Complex. Issue 48 (20th October 2015)

• Record Type: Journal Article
• Authors: Pascual‐Álvarez, Alejandro; Vallejo, Julia; Pardo, Emilio; Julve, Miguel; Lloret, Francesc; Krzystek, J.; Armentano, Donatella; Wernsdorfer, Wolfgang; Cano, Joan
• Is Part Of: Chemistry. Volume 21:Issue 48(2015)
• Page Start: 17299
• Page End: 17307
• Publication Date: 2015-10-20
• Subjects: complete active space (CAS) calculations -- EPR spectroscopy -- manganese -- porphyrinoids -- magnetic materials; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201502637
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: We report on a novel manganese(III)–porphyrin complex with the formula [Mn III (TPP)(3, 5‐Me2 pyNO)2 ]ClO4 ⋅CH3 CN (2 ; 3, 5‐Me2 pyNO=3, 5‐dimethylpyridine N ‐oxide, H2 TPP=5, 10, 15, 20‐tetraphenylporphyrin), in which the Mn III ion is six‐coordinate with two monodentate 3, 5‐Me2 pyNO molecules and a tetradentate TPP ligand to build a tetragonally elongated octahedral geometry. The environment in2 is responsible for the large and negative axial zero‐field splitting ( D =−3.8 cm −1 ), low rhombicity ( E /| D |=0.04) of the high‐spin Mn III ion, and, ultimately, for the observation of slow magnetic‐relaxation effects ( E a =15.5 cm −1 at H =1000 G) in this rare example of a manganese‐based single‐ion magnet (SIM). Structural, magnetic, and electronic characterizations were carried out by means of single‐crystal diffraction studies, variable‐temperature direct‐ and alternating‐current measurements and high‐frequency and ‐field EPR spectroscopic analysis followed by quantum‐chemical calculations. Slow magnetic‐relaxation effects were also observed in the already known analogous compound [Mn III (TPP)Cl] (1 ; E a =10.5 cm −1 at H =1000 G). The results obtained for1 and2 are compared and discussed herein. Abstract : Rarely seen : Field‐induced slow magnetic‐relaxation effects are observed in a manganese(III)–porphyrin complex with bis‐axial ligands for the first time (see figure). This complex is a rare example of a manganese‐based single‐ion magnet and expands the scope of metal‐coordination geometries that allow slow magnetic‐relaxation effects in mononuclear complexes.