Coulombic aggregations of Mn III salen-type complexes and keggin-type polyoxometalates: Isolation of Mn 2 single-molecule magnets

Yuki Sawada, Wataru Kosaka, Yoshihito Hayashi, Hitoshi Miyasaka

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44 Citations (Scopus)

Abstract

The reaction of Mn III salen-type complexes with di- and tetraanionic α-Keggin-type polyoxometalates (POMs) was performed, and three types of Coulombic aggregations containing Mn III out-of-plane dimeric units (abbreviated as [Mn 2] 2+) that are potentially single-molecule magnets (SMMs) with an S T = 4 ground state were synthesized: [Mn 2(5-MeOsaltmen) 2(acetone) 2][SW 12O 40] (1), [Mn 2(salen) 2(H 2O) 2] 2[SiW 12O 40] (2), and [Mn(5-Brsaltmen)(H 2O)(acetone)] 2[{Mn 2(5-Brsaltmen) 2}(SiW 12O 40)] (3), where 5-Rsaltmen 2- = N,N′-(1,1,2,2- tetramethylethylene)bis(5-R-salicylideneiminate) with R = MeO (methoxy), Br (bromo) and salen 2- = N,N′-ethylenebis(salicylideneiminate). Compound 1 with a dianionic POM, [SW 12O 40] 2-, is composed of a 1:1 aggregating set of [Mn 2] 2+/POM, and 2, with a tetraanionic POM, [SiW 12O 40] 4-, is a 2:1 set. Compound 3 with [SiW 12O 40] 4- forms a unique 1D coordinating chain with a [-{Mn 2}-POM-] 2- repeating unit, for which a hydrogen-bonded dimeric unit ([Mn(5-Brsaltmen) (H 2O)(acetone)] 2 2+) is present as a countercation. Independent of the formula ratio of [Mn 2] 2+/POM, Mn III dimers and POM units in 1-3 form respective segregated columns along a direction of the unit cell, which make an alternate packing to separate evenly identical species in a crystal. The nearest intermolecular Mn⋯Mn distance is found in the order 2 < 3 < 1. The segregation of the [Mn 2] 2+ dimer resulted in interdimer distances long enough to effectively reduce the intermolecular magnetic interaction, in particular in 1 and 3. Consequently, an intrinsic property, SMM behavior, of Mn III dimers has been characterized in this system, even though the interdimer interactions are still crucial in the case of 2, where a long-range magnetic order competitively affects slow relaxation of the magnetization at low ac frequencies.

Original languageEnglish
Pages (from-to)4824-4832
Number of pages9
JournalInorganic chemistry
Volume51
Issue number8
DOIs
Publication statusPublished - 2012 Apr 16
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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