Molecular Magnetism

Aromı́, Guillem; Gámez, Patrick; Roubeau, Olivier

doi:10.1002/9781118898277.ch12

Cited by 9 publications

(3 citation statements)

References 199 publications

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“…The N 6 coordination sphere provided to an iron(II) ion by two 4-substituted bis(2-pyridyl)-4H-1,2,4-triazole (Rdpt) ligands and two trans-thiocyanate coligands has yielded some nice examples of SCO active compounds. 9 We previously reported that a powder sample (single crystals proved elusive) of an iron(II) complex of an Rdpt ligand with a long alkyl tail, [Fe II (C 16 dpt) 2 (SCN) 2 ]• 2 / 3 H 2 O (3), exhibits room temperature SCO and forms a stable Langmuir film at an air−water interface. 7 Herein, we demonstrate that modification of the nature of the "tail" allows us to tune the SCO temperature by over 100 K. Specifically, we report and compare the iron(II) complexes of two new types of "tailed" Rdpt-based ligands padpt and hpdpt (Figure 1, amide-alkyl vs phenyl-fluorocarbon tails, i.e.…”

Section: ■ Introductionmentioning

confidence: 99%

“Tail” Tuning of Iron(II) Spin Crossover Temperature by 100 K

et al. 2015

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Two new Rdpt ligands featuring long "tails", padpt (N-4H-1,2,4-triazole-3,5-di(2-pyridyl)palmitamide) and hpdpt (4-(4-heptadecafluoroctylphenyl)-3,5-bis(2-pyridyl)-4H-1,2,4-triazole), were made and reacted with [Fe(II)(py)4(NCS)2] to give pinkish-red [Fe(II)(padpt)2(SCN)2] (1) and purple-red [Fe(II)(hpdpt)2(SCN)2] (2) as solvent-free crystals. Magnetic measurements reveal that both 1 and 2 exhibit complete and reproducible spin crossovers, with a far lower T1/2 for the amide-alkyl tailed 1 (182 K) than for the fluorocarbon tailed 2 (248 K), which in turn is far lower than the T1/2 of 290 K previously reported for the nonamide-alkyl tailed analogue [Fe(II)(C16dpt)2(SCN)2]·(2)/3H2O (3). Structure determinations for 1 and 2 in both the high spin (HS) and low spin (LS) states confirm the expected trans-NCS conformation and reveal that (a) the "tails" interdigitate and (b) the LS forms are less distorted than the HS forms (Σ = 58-70° vs 47-54°). DSC and Raman spectroscopy confirmed the high tail-dependence of the SCO events in 1 and 2, as well as in 3, with the Raman data giving T1/2 values of 190, 243, and 285 K, respectively. Bright orange single crystals of the solvatomorph [Fe(II)(hpdpt)2(SCN)2]·MeOH·H2O (2solv) were also structurally and magnetically characterized and, in contrast to 2, found to remain HS down to 4 K, providing further evidence of the huge impact of crystal packing on SCO. Both 1 and 2 form stable Langmuir films at an air-water interface, a single layer of which can be transferred to a solid support.

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Section: ■ Introductionmentioning

confidence: 99%

“Tail” Tuning of Iron(II) Spin Crossover Temperature by 100 K

et al. 2015

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“…It has been found that exchange coupling between metal centers is highly dependent on the conformation of the metal carboxylate bridges (Scheme ), the most common of them are syn-syn, syn-anti, and anti-anti modes . The syn-syn bridge pattern results in shorter metal···metal contacts leading to effective overlapping of magnetic orbitals.…”

Section: Magnetostructural Studies Of Manganese Aromatic Dicarboxylatesmentioning

confidence: 99%

Magneto-Structural Studies of Manganese(II) 2,4′-Benzophenone Dicarboxylate Based Coordination Polymers

Singh

Chernova

Ghosh

et al. 2022

Crystal Growth & Design

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The role of the N-donor auxiliary ligand in the formation of coordination polymers (CPs) has been examined for a series of Mn(II) aromatic dicarboxylate-based framework systems. The solvothermal reaction of L-shaped dicarboxylate with Mn(II) through a varying N-donor auxiliary ligand resulted in the crystallization of six new multinuclear Mn-based CPs:MnCP6 (where 2,4′-bpdc = benzophenone-2,4′-dicarboxylate, phen = 1,10 phenanthroline, 2,2′-bipy = 2,2′-bipyridine, 4,4′-dimethyl-2,2′-bipy = 4,4′-dimethyl-2,2′-bipyridine, and 5,5′-dimethyl-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine). The two 1D CPs, MnCP1 (square pyramidal) and MnCP2 (trigonal prism), respectively, were isolated from reactions in the absence and presence of an auxiliary ligand. The presence of phen led to anhydrous MnCP2 wherein C−H•••O interactions stabilized the 1D chains. The crystal packing in the hydrated MnCP1 is facilitated due to carboxylate oxygens interacting strongly with disordered lattice water. The auxiliary ligand, 2,2′-bipy and its derivatives in a suitable solvent led to the growth of four new solids built of a trimeric manganese cluster. MnCP3 is a layered solid while the methyl substituents on 2,2′-bipy altered the manganese carboxylate extended coordination in a different manner: (i) 4,4′-methyl substitution led to 1D (MnCP4) and 2D network (MnCP5); the bridging within the trimeric unit is also facilitated through in situ formed counter anions formate and acetate groups. (ii) 5,5′-Methyl substitution led to a 1D chain (MnCP6) where the trimeric unit occurred through the interference by another counter anion (chloride). The paper provides a mechanistic pathway for the observed crystal packing in terms of supramolecular condensation of soluble 1:1 manganese dicarboxylate complex species through a combination of coordination and H-bonding interactions. It also highlights how the supramolecular assembly is influenced when another competing soluble manganese complex coprecipitates, thus providing a rationale to the observed composition and coordination framework. All the manganese carboxylates showed antiferromagnetic behavior. The magnetic behavior of the two structurally comparable solids, MnCP1 and MnCP2, were further supported by highlevel first principle-based computations.

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“…One of the greatest challenges and goals in molecular magnetism is the ability to control spins at the single electron level. − This can be accomplished in heterometallic compounds largely by tuning the nature of localized versus delocalized orbitals that house unpaired electrons. Localized orbitals tend to be of either π or δ symmetry with respect to the metal–metal bond whereas delocalized orbitals tend to be of σ symmetry.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Paramagnetic Metal–Metal Bonded Heterometallic Complexes

Chipman

Berry

2020

Chem. Rev.

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Significant progress has been made in the past 10–15 years on the design, synthesis, and properties of multimetallic coordination complexes with heterometallic metal–metal bonds that are paramagnetic. Several general classes have been explored including heterobimetallic compounds, heterotrimetallic compounds of either linear or triangular geometry, discrete molecular compounds containing a linear array of more than three metal atoms, and coordination polymers with a heterometallic metal–metal bonded backbone. We focus in this Review on the synthetic methods employed to access these compounds, their structural features, magnetic properties, and electronic structure. Regarding the metal–metal bond distances, we make use of the formal shortness ratio (FSR) for comparison of bond distances between a broad range of metal atoms of different sizes. The magnetic properties of these compounds can be described using an extension of the Goodenough–Kanamori rules to cases where two magnetic ions interact via a third metal atom. In describing the electronic structure, we focus on the ability (or not) of electrons to be delocalized across heterometallic bonds, allowing for rationalizations and predictions of single-molecule conductance measurements in paramagnetic heterometallic molecular wires.

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Molecular Magnetism

Cited by 9 publications

References 199 publications

“Tail” Tuning of Iron(II) Spin Crossover Temperature by 100 K

“Tail” Tuning of Iron(II) Spin Crossover Temperature by 100 K

Magneto-Structural Studies of Manganese(II) 2,4′-Benzophenone Dicarboxylate Based Coordination Polymers

Paramagnetic Metal–Metal Bonded Heterometallic Complexes

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