Effects of alternation in some quasi-one-dimensional magnetic materials

Abstract

Exchange coupling in Cu(II) and Mn(II1) compounds with unusual structures is discussed. {[Cu( bipyrimidine) (OH) (H,O)] ( ClO,) }, has an alternatingly bridged structure with alternating ferromagnetic ( + 167.6 cm -' through the hydroxo bridge) and antiferromagnetic ( -79.8 cm -' through the bipyrimidine bridge) interactions. Copper( II) phthalate monohydrate has alternating next-nearest-neighbor exchange with J--12.3 cm -' and a = 0.06. This is the first member of this class. The compound K,[Mn( III) (salicylate) J[Mn ( III) (salicylate) J{CH,OH], has manganese ions in two environments alternating along the chain. A modified model for the chain is presented, and exchange coupling is found to be small since magnetic orbitals are not linked by the bridging ligand.

Open and closed copper chain coordination polymers with alternating ferromagnetic and antiferromagnetic interactions

“…The apical Cu1-O5 distance of 2.173(3) A ˚is 0.212 A ˚longer than the mean Cu-O distance of 1.951 A ˚in the equatorial plane, which is slightly shorter than 2.258 A ˚of the axial Cu-O distance in the square pyramidal geometry. 13 Cu1-O and Cu1-N distances in the equatorial plane are in good agreement with those of the reported compounds. 13,18 The residual two O atoms of the amino acetic groups bind to one intrablock and one interblock Cu 2+ centers along their square plane, respectively.…”

“…13 Cu1-O and Cu1-N distances in the equatorial plane are in good agreement with those of the reported compounds. 13,18 The residual two O atoms of the amino acetic groups bind to one intrablock and one interblock Cu 2+ centers along their square plane, respectively. That is, each HL 3À afforded one such carboxylic oxygen atom to link the adjacent trinuclear units through binding to the six coordinate copper(II) ions along their equatorial plane, meanwhile the two short arms at the N atom bridge both the intraunit and interunit Cu1 and Cu2 via carboxylate groups in a syn-anti fashion.…”

“…Especially, various bridging modes such as syn-syn, syn-anti and anti-anti configuration and bridging tridentate to two metal centers, may lead to different magnetic interactions in paramagnetic metal ions. 12,13 In contrast, polycarboxylate ligands with asymmetric structure are less utilized in constructing organic-inorganic coordination polymers. 14 Attracted by the various frameworks and interesting magnetic behavior of polycarboxylate complexes, we introduced 2-(bis(carboxymethyl)amino)terephthalic acid (H 4 L) as a precursor ligand with the aim to explore some new magnetic systems.…”

Magnetic Coupling through the Carbon Skeleton of Malonate in Two Polymorphs of {[Cu(bpy)(H2O)][Cu(bpy)(mal)(H2O)]}(ClO4)2 (H2mal = Malonic Acid; bpy = 2,2‘-Bipyridine)

“…During the past 2 decades, one-dimensional magnetic systems have been thoroughly investigated, mainly because they are suitable examples for developing theoretical models aimed at understanding the exchange interaction in extended lattices. − Among the great variety of homometallic one-dimensional magnetic complexes which have been characterized, one of the more interesting is that where regular alternating ferro- and antiferromagnetic interactions occurs. − This is a rare situation because the difficulty of designing a ferromagnetically coupled unit which could act as complex ligand toward the same metal ion yielding a chain with regular alternating bridges and sign of magnetic interactions. The regular alternating of bis(chelating) 2,2‘-bipyrimidine (bpm, the antiferromagnetic coupler) and di-μ-hydroxo groups (the ferromagnetic coupler) in copper(II) chains provided examples of these materials .…”

An Azide-Bridged Copper(II) Ferromagnetic Chain Compound Exhibiting Metamagnetic Behavior

“…One-dimensional alternating chain compounds frequently result from the reaction of metal salts with a combination of different ligands with multiple bridge capacity, e.g. bpm (2,2‘-bipyrimidine) and OH, − or bpm and oxalate. , Alternating ferromagnetic and antiferromagnetic exchange terms have been assigned to the complexes {[Cu(bpm)(OH)(H 2 O)](ClO 4 )} n 1 and {[Cu(bpm)(OH)(NO 3 )]·H 2 O} n , with the alternating bis(μ 2 -hydroxy) fragments responsible for the ferromagnetic components. The small Cu−OH−Cu angles (95.5 and 95.7°, respectively) fall in the ferromagnetic realm for dinuclear systems with the same spin-coupled core, which were shown by Hatfield et al.…”