(EtN)[W(DAPBH)(CN)], the first pentagonal-bipyramidal W(III) complex with unquenched orbital angular momentum: a novel Ising-type magnetic building block for single-molecule magnets.

The first pentagonal-bipyramidal tungsten(III) complex (EtN)[W(DAPBH)(CN)] with a NO-type Schiff-base ligand and two apical cyanide groups was synthesized and characterized structurally and magnetically. The complex has a low-spin ( = 1/2) ground state and features unquenched orbital angular momentum = ±1 causing very strong Ising-type magnetic anisotropy.

Pentagonal-bipyramidal 4d and 5d complexes with unquenched orbital angular momentum as a unique platform for advanced single-molecule magnets: current state and perspectives.

This article overviews the current state and prospects of the concept of advanced single-molecule magnets (SMMs) based on low-spin ( = 1/2) pentagonal-bipyramidal (PBP) 4d and 5d complexes with unquenched orbital angular momentum. This approach is based on the unique property of PBP 4d and 5d complexes to cause highly anisotropic spin coupling of perfect uniaxial symmetry, -zizj - (xixj + yiyj), regardless of the local geometric symmetry. The M(4d/5d)-M(3d) exchange-coupled pairs in the apical positions of the PBP complexes produce Ising-type exchange interactions (|| > ||), which serve as a powerful source of uniaxial magnetic anisotropy of a SMM cluster.

(EtN)[Mo(DAPBH)Cl], the first pentagonal-bipyramidal Mo(iii) complex with a NO-type Schiff-base ligand: manifestation of unquenched orbital momentum and Ising-type magnetic anisotropy.

The first paramagnetic pentagonal-bipyramidal complex of Mo(iii) with a N3O2-type Schiff-base ligand was synthesized by the comproportionation reaction between Mo(ii) and Mo(iv) congeners. The complex has a low-spin (S = 1/2) ground state of MoIII(4d3) with double orbital degeneracy and unquenched orbital momentum, which result in strong Ising-type magnetic anisotropy.

A new Mo(iv) complex with the pentadentate (NO) Schiff-base ligand: the first non-cyanide pentagonal-bipyramidal paramagnetic 4d complex.

A heptacoordinate complex [Mo(DAPBH)Cl] (HDAPBH is 1,1'-(pyridine-2,6-diyl)bis(ethan-1-yl-1-ylidene)dibenzohydrazine) has been synthesized and characterized structurally and magnetically. It exhibits a slightly distorted pentagonal bipyramidal geometry and reveals paramagnetic behaviour resulting from two unpaired electrons (S = 1) with large positive zero-field splitting (D = +50 cm) and pronounced temperature-independent paramagnetism.