A large negative magnetoresistance effect in semiconducting crystals composed of an octahedrally ligated phthalocyanine complex with high-spin manganese(iii).

A design for an octahedrally ligated phthalocyanine complex with high-spin manganese(iii) ( = 2) and Mn(Pc)Cl (Pc = phthalocyanine) is presented. The presence of high-spin state Mn in the fabricated PhP[Mn(Pc)Cl] (PhP = tetraphenylphosphonium) semiconducting molecular crystal is indicated by the Mn-Cl distance, which suggests an electronic configuration of (d , d )(d )(d ). This was confirmed by the Curie constant ( = 5.69 emu K mol), which was found to be significantly larger than that of the isostructural PhP[Mn(Pc)(CN)], where Mn adopts a low-spin state ( = 1). The magnetoresistance (MR) effects of PhP[Mn(Pc)Cl] at 26.5 K under 9 T static magnetic fields perpendicular and parallel to the -axis were determined to be -30% and -20%, respectively, which are significantly larger values than those of PhP[Mn(Pc)(CN)]. Furthermore, the negative MR effect is comparable to that of PhP[Fe(Pc)(CN)] ( = 1/2), which exhibits the largest negative MR effect reported for [M(Mc)L]-based systems (Mc = macrocyclic ligand, L = axial ligand). This suggests that the spin state of the metal ion is the key to tuning the MR effect.