(Et₄N)[Mo^III(DAPBH)Cl₂], the first pentagonal-bipyramidal Mo(iii) complex with a N₃O₂-type Schiff-base ligand: manifestation of unquenched orbital momentum and Ising-type magnetic anisotropy

Abstract

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.

Magnetic anisotropy of transition metal and lanthanide ions in pentagonal bipyramidal geometry

“…Detailed magnetic studies down to 2 K have been reported for a structurally rigid complex, NEt 4 [Mo(L1 Ph )Cl 2 ], and its behavior rationalized by ligand field calculations. 25 Such compounds are not expected to exhibit magnetic anisotropy (ZFS takes place only for S > ½) but unquenched orbital momentum occurs. Due to orbital degeneracy and strong spin–orbit coupling, the ground state of the PBP complex is split into two Kramers doublets ( φ (±1/2) and χ (±1/2) in Fig.…”

Slow Magnetic Relaxation, Antiferromagnetic Ordering, and Metamagnetism in MnII(H2dapsc)‐FeIII(CN)6Chain Complex with Highly Anisotropic Fe‐CN‐Mn Spin Coupling

“…The chain complex was also obtained in the reaction between [Fe(H 2 dapbh)Cl 2 ] and [Ni(CN) 4 ] 2− , which showed field‐induced slow magnetic relaxation . Two pentanuclear complexes [{M(L)} 3 {W(CN) 8 } 2 (H 2 O) 2 ] (M=Ni, L=H 2 dapbh; M=Fe, L=H 2 dapbih) exhibiting SMM behavior were also synthesized …”

“…These complexes are promising building blocks for tailoring low‐dimensional polynuclear assemblies, particularly due to the presence of labile apical ligands, which are easily replaced with bridging cyanometallate complexes. Despite the fact that the complexes of H 2 dapsc and related ligands have been known since 1973, their use for the preparation of magnetic polynuclear structures began only recently . However, several important 1D compounds have been synthesized, such as bimetallic chain complexes based on [M(H 2 dapsc)Cl 2 ] 0 (M=Mn II and Fe II ) units in combination with [Fe(CN) 5 NO] 2− , [Mn(CN) 6 ] 3− (M=Mn II ) and [Cr(dapbh)(CN) 2 ] (M=Fe II ).…”

“…These complexes reveal a rather rare pentagonal‐bipyramidal coordination around the central metal atom resulting from the five donor atoms (N 3 O 2 ), forming a pentagon in the equatorial plane of the nearly planar H 2 dapsc ligand and two ligands (solvent and/or Cl, NO 3 ) in the apical positions of the bipyramid . Recently, it has been shown that some of these Co II , Fe II , Dy III and Er III mononuclear complexes with the H 2 dapbh, H 2 dapsc and H 4 daps ligands (Scheme ) are SMMs demonstrating slow magnetic relaxation under a static dc field . These complexes are promising building blocks for tailoring low‐dimensional polynuclear assemblies, particularly due to the presence of labile apical ligands, which are easily replaced with bridging cyanometallate complexes.…”

A Series of Novel Pentagonal-Bipyramidal Erbium(III) Complexes with Acyclic Chelating N3O2 Schiff-Base Ligands: Synthesis, Structure, and Magnetism

“…Experimental and theoretical studies of seven-coordinated metal centers with pentagonal-bipyramidal (PBP) geometry (with a pseudo D 5h symmetry) show that such centers are promising as anisotropic spin carriers [9,11,[16][17][18][19][20][21][22][23][24]. As a result, new PBP complexes of 3d, 4d, 5d and 4f metals have been synthesized in recent years [25][26][27][28][29][30][31][32][33][34]. Among them, of special note are the seven-coordination PBP Dy complexes displaying high U eff and T B values, up to 1800 K and 20 K, respectively [3,19,[30][31][32][33][34].…”