New Approach for Designing Single-Chain Magnets: Organization of Chains via Hydrogen Bonding between Nucleobases

Two one-dimensional (1D) manganese complexes, [Mn₂(naphtmen)₂(L)]­(ClO₄)·2Et₂O·2MeOH·H₂O (<b>1</b>) and [Mn₂(naphtmen)₂(HL)]­(ClO₄)₂·MeOH (<b>2</b>), were synthesized by using a bridging ligand with a nucleobase moiety, 6-amino-9-β-carboxyethylpurine, and a salen-type manganese­(III) dinuclear complex, [Mn₂(naphtmen)₂(H₂O)₂]­(ClO₄)₂ (naphtmen^2– = <i>N</i>,<i>N</i>′-(1,1,2,2-tetramethylethylene)­bis­(naphthylideneiminato) dianion). In <b>1</b> and <b>2</b>, the carboxylate-bridged Mn^III dinuclear units are alternately linked by two kinds of weak Mn···O interactions into 1D chains. As a result, canted antiferromagnetic and ferromagnetic interactions are alternately present along the chains, leading to a 1D chain with non-cancellation of anisotropic spins. Since the chains connected via H-bonds between nucleobase moieties are magnetically isolated, both <b>1</b> and <b>2</b> act as single-chain magnets (SCMs). More importantly, this result shows the smaller canting angles hinder long-range ordering in favor of SCM dynamics

New Approach for Designing Single-Chain Magnets: Organization of Chains via Hydrogen Bonding between Nucleobases

Two one-dimensional (1D) manganese complexes, [Mn₂(naphtmen)₂(L)]­(ClO₄)·2Et₂O·2MeOH·H₂O (<b>1</b>) and [Mn₂(naphtmen)₂(HL)]­(ClO₄)₂·MeOH (<b>2</b>), were synthesized by using a bridging ligand with a nucleobase moiety, 6-amino-9-β-carboxyethylpurine, and a salen-type manganese­(III) dinuclear complex, [Mn₂(naphtmen)₂(H₂O)₂]­(ClO₄)₂ (naphtmen^2– = <i>N</i>,<i>N</i>′-(1,1,2,2-tetramethylethylene)­bis­(naphthylideneiminato) dianion). In <b>1</b> and <b>2</b>, the carboxylate-bridged Mn^III dinuclear units are alternately linked by two kinds of weak Mn···O interactions into 1D chains. As a result, canted antiferromagnetic and ferromagnetic interactions are alternately present along the chains, leading to a 1D chain with non-cancellation of anisotropic spins. Since the chains connected via H-bonds between nucleobase moieties are magnetically isolated, both <b>1</b> and <b>2</b> act as single-chain magnets (SCMs). More importantly, this result shows the smaller canting angles hinder long-range ordering in favor of SCM dynamics

New Approach for Designing Single-Chain Magnets: Organization of Chains via Hydrogen Bonding between Nucleobases

Two one-dimensional (1D) manganese complexes, [Mn₂(naphtmen)₂(L)]­(ClO₄)·2Et₂O·2MeOH·H₂O (<b>1</b>) and [Mn₂(naphtmen)₂(HL)]­(ClO₄)₂·MeOH (<b>2</b>), were synthesized by using a bridging ligand with a nucleobase moiety, 6-amino-9-β-carboxyethylpurine, and a salen-type manganese­(III) dinuclear complex, [Mn₂(naphtmen)₂(H₂O)₂]­(ClO₄)₂ (naphtmen^2– = <i>N</i>,<i>N</i>′-(1,1,2,2-tetramethylethylene)­bis­(naphthylideneiminato) dianion). In <b>1</b> and <b>2</b>, the carboxylate-bridged Mn^III dinuclear units are alternately linked by two kinds of weak Mn···O interactions into 1D chains. As a result, canted antiferromagnetic and ferromagnetic interactions are alternately present along the chains, leading to a 1D chain with non-cancellation of anisotropic spins. Since the chains connected via H-bonds between nucleobase moieties are magnetically isolated, both <b>1</b> and <b>2</b> act as single-chain magnets (SCMs). More importantly, this result shows the smaller canting angles hinder long-range ordering in favor of SCM dynamics

Chiral Single-Chain Magnet: Helically Stacked [Mn^III₂Cu^II] Triangles

The one-dimensional complex [Mn^III₂Cu^II(μ₃-O)­(Cl-sao)₃(EtOH)₂]·EtOH (Mn₂Cu) was obtained by the metal replacement reaction of the trinuclear manganese complex (Et₃NH)­[Mn^III₃(μ₃-O)­Cl₂(Cl-sao)₃(MeOH)₂(H₂O)₂] with [Cu­(acac)₂]. The Mn₂Cu chain exhibits single-chain-magnet behavior with finite-size effects due to its large magnetic anisotropy

Cyanide-Bridged Decanuclear Cobalt–Iron Cage

A cyanide-bridged decanuclear [Co₆Fe₄] cluster was synthesized by a one-pot reaction, and the magnetic properties and electronic configuration were investigated. The complex displayed thermally controlled electron-transfer-coupled spin transition (ETCST) behavior between Co^III low-spin–NC–Fe^II low-spin and Co^II high-spin–NC–Fe^III low-spin states, as confirmed by single-crystal X-ray, magnetic, and Mössbauer analyses

Multiredox Active [3 × 3] Copper Grids

A nonanuclear copper grid complex, [Cu^II₉(L)₆]­(BF₄)₆·1-PrOH·5H₂O (<b>1</b>·1-PrOH·5H₂O; L = 2,6-bis­[5-(2-pyridinyl)-1<i>H</i>-pyrazol-3-yl]­pyridine), was synthesized with a [3 × 3] grid structure consisting of nine Cu^II ions and six deprotonated ligands and displayed four-step quasi-reversible redox behavior from [Cu^II₉] to [Cu^I₄Cu^II₅]. The corresponding heterovalent complex [Cu^I₂Cu^II₇(L)₆]­(PF₆)₄·3H₂O (<b>2</b>·3H₂O) was successfully isolated and had a distorted core structure that radically changed the intramolecular magnetic coupling pathways

Intermediate-Spin Iron(III) Complexes Having a Redox-Noninnocent Macrocyclic Tetraamido Ligand

An iron­(III) complex having a dibenzotetraethyltetraamido macrocyclic ligand (DTTM^4–), (NEt₄)₂[Fe^III(DTTM)­Cl] (<b>1</b>), was synthesized and characterized by crystallographic, spectroscopic, and electrochemical methods. Complex <b>1</b> has a square-pyramidal structure in the <i>S</i> = ³/₂ spin state. The complex exhibited two reversible redox waves at +0.36 and +0.68 V (vs SCE) in the cyclic voltammogram measured in CH₂Cl₂ at room temperature. The stepwise oxidation of <b>1</b> using chemical oxidants allowed us to observe clear and distinct spectral changes with distinct isosbestic points for each step, in which oxidation occurred at the phenylenediamido moiety rather than the iron center. One-electron oxidation of <b>1</b> by 1 equiv of [Ru^III(bpy)₃]­(ClO₄)₃ (bpy = 2,2′-bipyridine) in CH₂Cl₂ afforded square-pyramidal (NEt₄)­[Fe­(DTTM)­Cl] (<b>2</b>), which was in the <i>S</i> = 1 spin state involving a ligand radical and showed a slightly distorted square-pyramidal structure. Complex <b>2</b> showed an intervalence charge-transfer band at 900 nm, which was assigned on the basis of time-dependent density functional theory calculations, to indicate that the complex is in a class IIA mixed-valence ligand-radical regime with <i>H</i>_ab = 884 cm^–1. Two-electron oxidation of <b>1</b> by 2 equiv of [(4-Br-Ph)₃N^•+]­(SbCl₆) in CH₂Cl₂ afforded two-electron-oxidized species of <b>1</b>, [Fe­(DTTM)­Cl] (<b>3</b>), which was in the <i>S</i> = ¹/₂ spin state; complex <b>3</b> exhibited a distorted square-pyramidal structure. X-ray absorption near-edge structure spectra of <b>1</b>–<b>3</b> were measured in both CH₃CN solutions and BN pellets to observe comparable rising-edge energies for the three complexes, and Mössbauer spectra of <b>1</b>–<b>3</b> showed almost identical isomer shifts and quadruple splitting parameters, indicating that the iron centers of the three complexes are intact to be in the intermediate-spin iron­(III) state. Thus, in complexes <b>2</b> and <b>3</b>, it is evident that antiferromagnetic coupling is operating between the unpaired electron(s) of the ligand radical(s) and those of the iron­(III) center