A Mixed 3d−4f 14-Metallacrown-5 Complex That Displays Slow Magnetic Relaxation through Geometric Control of Magnetoanisotropy

Abstract

We describe the synthesis and magnetic properties of a unique mixed 3d-4f 14-metallacrown-5 complex. This is the first metallacrown family to feature μ-O and μ-OH bridges as well as to incorporate a Ln(III) ion into the ring. Alternating-current SQUID magnetometry of the Tb, Dy, and Ho derivatives reveals slow magnetic relaxation, a hallmark property of single-molecule magnets. For the Dy structure (4), an effective energy barrier U(eff) of 16.7 K and a relaxation time of 4.9 × 10(-8) s were calculated. Because of the relatively small total spin, this behavior most likely results from a large magnetoanisotropy, which is controlled through geometric constraints.

Route to Metallacrowns: The Mechanism of Formation of a Dinuclear Iron(III)-Salicylhydroxamate Complex

“…27 More recently, metallacrowns have been found to function as single molecule magnets. 28,29 Salicylhydroxamic acid contains both hydroxymate and phenolate donor atoms and is well suited to synthesize metallacrowns, The reaction pathway is discussed in terms of a multistep mechanistic scheme in which the metalÀligand interaction is coupled to hydrolysis and self-aggregation steps of Iron(III). The observation and characterization of M 2 L as a stable species is important because it contains the ÀFe-O-N-FeÀ sequence, which constitutes the repetitive motif of the SHA-based metallacrown ring and provides the rationale for 12-MC-4 metallacrowns.…”

“…27 More recently, metallacrowns have been found to function as single molecule magnets. 28,29 Salicylhydroxamic acid contains both hydroxymate and phenolate donor atoms and is well suited to synthesize metallacrowns, Scheme 1 ABSTRACT: The equilibria and the kinetics of the binding of Iron(III) to salicylhydroxamic (SHA) and benzohydroxamic (BHA) acids have been investigated in aqueous solution (I = 1 M (HClO 4 / NaClO 4 ), T = 298 K) using spectrophotometric and stopped-flow methods. Whereas Iron(III) forms a 1:1 complex (ML) with BHA, it forms both ML and M 2 L complexes with SHA.…”

Assembly of oximate-bridged Mn6 cluster to a one-dimensional chain

“…Magnetic studies show that both complexes display slow magnetization relaxation.Oximato-bridged complexes have attracted great attention in the field of molecular magnets [1-3] since exciting single-molecule magnets (SMMs) and single-chain magnets (SCMs) have been observed in some oximato-bridged Mn(III) complexes [4][5][6]. Currently, salicylaldoxime (H 2 salox) and its derivatives have been widely investigated for the construction of polynuclear complexes of formula [Mn 6 O 2 (R-salox) 6 (O 2 CR) 2 L 4-6 ] (H 2 R-salox = R-substituted salicylaldoxime; R = H, Me, Et, Ph etc.…”

A Family of 12‐Azametallacrown‐4 Structural Motif with Heterometallic MnIII‐Ln‐MnIII‐Ln (Ln=Dy, Er, Yb, Tb, Y) Alternate Arrangement and Single‐Molecule Magnet Behavior

“…For example, two [22‐MC‐8] metallacrowns [Mn 6 Ln 4 (H 2 shi) 2 (shi) 6 (sal) 2 (O 2 CCH 3 ) 4 (OH) 2 (CH 3 OH) 8 ] ⋅ 4 CH 3 OH (Ln=Ho, Dy; sal=salicylic acid),1b, 11 and three [28‐MC‐10] MCs [Mn 6 Ln 6 (H 2 shi) 4 (Hshi) 2 (shi) 10 (CH 3 OH) 10 (H 2 O) 2 ] (Ln=Tb, Dy and Gd)1b exhibited such structures with 3d–4f metal ions in the rings and showed slow relaxation of magnetization. Three [14‐MC‐5] MCs, [Ln 2 Mn 4 O(shi) 4 (OH)(OAc)(NO 3 ) 2 ] ⋅ 3 C 3 H 7 NO ⋅ 7 C 5 H 5 N ⋅ H 2 O (Ln=Tb, Dy, Ho) also incorporated Ln ions in the rings, and the Dy complex showed an effective energy barrier of 16.7 K 12. However, the formation of the above 3d–4f MCs is limited to hydroxamic acid ligands, which chelate metal ions to form five‐membered rings through hydroxylimino and carbonyl oxygen and six‐membered rings through hydroxylamine nitrogen and phenolate oxygen atoms.…”