Abrupt Spin‐State Switching in Mn(III) Complexes with BPh₄ Anion: Effect of Halide Substituents on Crystal Structure and Magnetic Properties.

Abstract

Three tetraphenylborates of mononuclear Mn(III) cation complexes with hexadentate ligands, the products of the reaction between a N,N'-bis(3-aminopropyl) ethylenediamine and salicylaldehydes with the different haloid substitutions at the 5 or 3,5 positions, have been synthesized: [Mn(5-F-sal-N-1,5,8,12)]BPh 4 (1), [Mn(3,5-diCl-sal-N-1,5,8,12)]BPh 4 (2) and [Mn(3,5-Br,Cl-sal-N-1,5,8,12)]BPh 4 (3). Their crystal structure, dielectric constant (ɛ) and magnetic properties have been studied. Ligand substituents have a dramatic effect on the structure and magnetic properties of the complexes. With decreasing temperature, the complex (1) shows a gradual spin crossover from the high-spin state (HS) to the HS:LS intermediate phase, followed by an abrupt transition to the low-spin state (LS) without changing the crystal symmetry. The complexes 2 and 3 are isostructural, but have fundamentally different properties. Complex 2 demonstrates two structural phase transitions related to

Domain Wall Dynamics in a Ferroelastic Spin Crossover Complex with Giant Magnetoelectric Coupling

“…A report on the magnetic and dielectric properties of [Mn III (3,5-diCl-sal 2 (323))]BPh 4 together with crystallographic data for three of the four structural phases has been published during the revision process for this article, see ref ( 108 ).…”

The effect of fluorine substituents on the crystal structure and spin crossover behavior of the cation [MnIII(3,5-diHal-sal2323)]+ complex family with BPh4 anions

“…Changes in the Mn–N bond lengths and octahedral distortion parameters with decreasing temperature are almost the same in both complexes (Table 1). A common supramolecular feature of these complexes, as well as other similar systems showing spin transformations, 27–30 is the presence in their structures of intermolecular N–H⋯π Ph ⋯H–N cation–anion interactions with the formation of one-dimensional chains. In contrast to the monoclinic polymorph ( 2 ), the triclinic polymorph ( 3 ), in which the cation–anion N–H⋯π Ph interactions are only a discrete character (Fig.…”

“…It is well known that the cation–anion non-covalent intermolecular interactions, particularly N–H⋯X interactions between the Mn( iii ) cationic complex and counter anions, can play a significant role in determining the spin-state switching behavior. 6,11,17–19,26–30…”

“…9–26 The development of these approaches has recently led to the synthesis of tetraphenylborates of Mn( iii ) complexes with a sal 2 323 ligand containing dihalide (Cl, Br) substituents on the phenolate ring: [Mn(3,5-diCl-sal 2 323)]BPh 4 ( 4 ), [Mn(3,5-Br,Cl-sal 2 323)]BPh 4 ( 5 ) and [Mn(3,5-diBr-sal 2 323)]BPh 4 ( 6 ) which showed unusual structural and magnetic properties. 27–30 All three complexes are isostructural, but have fundamentally different properties. Dichlorine-containing complex 4 shows three structural phase transitions, two of which are associated with sharp spin crossovers from HS to the HS:LS intermediate phase at 137 K and from the intermediate phase to the LS at 82 K. The nature of the dihalogen substituents (chloride and bromide) has a dramatic effect on the properties of these complexes: even the replacement of one chlorine by bromine changes the character and temperature of the phase and spin transitions.…”

“…To the best of our knowledge, there are only two works that describe Mn( iii ) complexes with the monofluoro-substituted sal 2 323 ligand and various counterions. 25,29 As regards difluoro- and mixed F,Br-substituted ligands, they were used for the first time in the present work. We purposefully preferred tetraphenylborate as a counterion, since the use of this anion made it possible to study the influence of the nature of dihalide substituents on the magnetic behavior and structure of complexes, excluding the influence of the anion and lattice solvents.…”