Dinuclear Copper(<scp>II</scp>) Complexes of Two Homologous Pyrazine‐Based Bis(terdentate) Diamide Ligands

Klingele, Julia; Moubaraki, Boujemaa; Murray, Keith S.; Boas, John F.; Brooker, Sally

doi:10.1002/ejic.200400908

Cited by 33 publications

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References 45 publications

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“…Long colorless needle-like crystals of tolpyph suitable for X-ray diffraction were grown by slow evaporation of a solution of tolpyph in 5:1 CH 2 Cl 2 /CH 3 OH (Figure S2). As usual for Rdpt -like ligands, the pyridine nitrogen atom N(1) is pointing toward the tolyl group and not toward the N(2) nitrogen atom of the triazole ring due to the repulsion between the lone pairs of electrons of the pyridine and triazole nitrogens. ,− In 1,2,4-triazole systems with an aromatic ring as the 4 N -substituent the ring is usually twisted almost perpendicular to the triazole ring, ,− ,− while the other ring substituents at 3 C and 5 C on the triazole are usually close to being coplanar with the triazole ring. This is also the case for tolpyph (tolyl vs triazole 69.63°; pyridine vs triazole 29.63°; phenyl vs triazole 33.89°).…”

Section: Resultsmentioning

confidence: 99%

Solid Versus Solution Spin Crossover and the Importance of the        Fe–N≡C(X) Angle

Rodríguez‐Jiménez

Brooker

2017

Inorg. Chem.

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A new family of mononuclear [Fe(Rdpt)(NCE)] complexes (E = S, Se, or BH) is formed by 1:2 reaction of [Fe(pyridine)(NCE)] with the monotopic pyridyl triazole ligand 4-(4-methylphenyl)-3-(2-pyridinyl)-5-phenyl-4H-1,2,4-triazole (tolpyph). The three complexes are obtained as six different solvatomorphs: [Fe(tolpyph)(NCS)]·HO (1·HO), 1·1.5CHOH·0.5HO, [Fe(tolpyph)(NCSe)] (2), 2·1.5HO, [Fe(tolpyph)(NCBH)] (3), and 3·HO. Single-crystal X-ray diffraction reveals that 1·1.5CHOH·0.5HO and 2 are high-spin (HS) at 100 K, while 3 is low-spin (LS) at 100 K and HS at 373 K. Compound 3 is the first structurally characterized example of an [Fe(Rdpt)(NCE)]-type complex with NCBH co-ligand: the crystal packing is dominated by aromatic stacking interactions. Solid-state magnetic measurements show that 1·HO and 2·1.5HO remain HS down to 50 K, whereas 3·HO undergoes spin crossover (SCO) with a T of 309 K, slightly above room temperature. A literature survey of analogous trans-[Fe(Rdpt)(NCX)]-type complexes (53 distinct crystal structures) shows that for the complexes that are SCO active in the solid state the Fe-N≡C(X) angle is usually close to straight, 162-178°, whereas it is usually lower, 142-159°, for the complexes that remain HS. UV-vis studies in CHCl solution show that in each case the use of a 6:1 ratio of tolpyph/Fe(II) is required to ensure the iron(II) is present in solution as [Fe(tolpyph)(NCE)]. Interestingly, using this ratio, all three compounds are SCO-active in CDCl solution-in dramatic contrast to the solid-state findings. Specifically, while compounds 1 and 2 are not SCO-active in the solid state (they remain HS), they undergo gradual SCO in CDCl solution, with T values of 290 and 310 K, respectively. In CDCl solution, compound 3 has a T value of 288 K, which is 21 K lower than in the solid state. These results highlight the differences between solid state (ligand field; crystal packing) and solution (ligand field; solvation) effects on SCO, with the latter studies revealing room-temperature SCO for all three of these complexes.

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Section: Resultsmentioning

confidence: 99%

Solid Versus Solution Spin Crossover and the Importance of the        Fe–N≡C(X) Angle

Rodríguez‐Jiménez

Brooker

2017

Inorg. Chem.

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Ammonium, Alkylammonium, and Amino Acid Complexes of a Hexacopper Fluoro‐Metallacrown Cavitand

Jones

Barrett

Kilner

et al. 2007

Chemistry A European J

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Reaction of CuF2 with one equivalent of 3{5}-(pyrid-2-yl)-5{3}-(tertbutyl)pyrazole (HL) and excess NH4OH in MeOH affords crystalline [NH4{Cu(micro-F)(microL)}6(CH2Cl2)2]HF2 in moderate yield. This compound contains the 12-MC-6 metallacrown [{Cu(micro-F)(micro-L)}6] (1) with a NH4 + ion at its center, and CH2Cl2 molecules complexed in bowl-shaped cavities above and below the Cu6F6 ring. Similar reactions using the bases MeNH2, glycine, l-alanine or beta-alanine afforded solvated crystals of [1(H3NMe)2]Cl2, [1(gly)2], [1(l-ala)2], and [1(beta-ala)2], respectively. The metallacrown 1 in these products contains methylammonium and zwitterionic amino-acid guests in its two bowl-shaped cavities; each of the amino acids hydrogen-bonds to three F atoms. A related reaction using 1,6-diaminohexane resulted in fixation of CO2 from the air to give solvated [1(H3NC6H12NHCO2)2], again with a zwitterionic guest. NMR, ESI-MS and UV/vis measurements suggest that the metallacrown 1 retains its integrity in several organic solvents, although it is unclear to what extent guest binding takes place in solution.

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Self‐Assembly of Cyclohelicate [M₃L₃] Triangles Over [M₄L₄] Squares, Despite Near‐Linear Bis‐terdentate L and Octahedral M

Hogue

Dhers

Hellyer

et al. 2017

Chemistry A European J

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Self-assembly of 1:1:2 M (BF ) (M=Zn or Fe), pyrazine-2,5-dicarbaldehyde (1) and 2-(2-aminoethyl)pyridine gave trimetallic triangle architectures rather than the anticipated tetrametallic [2×2] squares. Options for the nontrivial synthesis of 1 are considered, and synthetic details provided for both preferred routes. Rare cyclohelicate triangle architectures are observed for the pair of structurally characterized yellow-brown [Zn L ](BF ) and dark green [Fe L ](BF ) complexes of the neutral bis-terdentate Schiff base L. In order to form these pyrazine-edged triangles, the octahedral metal ions-with all 6 N-donors provided by the terdentate binding pockets of two L-are located 0.4-0.5 Å out of the plane of the bridging pyrazines, towards the center of the triangle. Density functional theory calculations confirm that simple particle counting entropic arguments, which predict triangles over squares, are correct here, with the triangles shown to be energetically favored over the corresponding squares. However, importantly, DFT analysis of these and related triangle versus square systems also show that vibrational contributions to entropy dominate and may significantly influence the preferred architecture, such that simple particle counting cannot in general be reliably employed to predict the observed architecture.

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Dinuclear Copper(II) Complexes of Two Homologous Pyrazine‐Based Bis(terdentate) Diamide Ligands

Abstract: The 1:1 reactions of the new bis(terdentate) diamide ligand N,

Cited by 33 publications

References 45 publications

Solid Versus Solution Spin Crossover and the Importance of the        Fe–N≡C(X) Angle

Solid Versus Solution Spin Crossover and the Importance of the        Fe–N≡C(X) Angle

Ammonium, Alkylammonium, and Amino Acid Complexes of a Hexacopper Fluoro‐Metallacrown Cavitand

Self‐Assembly of Cyclohelicate [M₃L₃] Triangles Over [M₄L₄] Squares, Despite Near‐Linear Bis‐terdentate L and Octahedral M

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Dinuclear Copper(II) Complexes of Two Homologous Pyrazine‐Based Bis(terdentate) Diamide Ligands

Abstract: The 1:1 reactions of the new bis(terdentate) diamide ligand N,

Cited by 33 publications

References 45 publications

Solid Versus Solution Spin Crossover and the Importance of the Fe–N≡C(X) Angle

Solid Versus Solution Spin Crossover and the Importance of the Fe–N≡C(X) Angle

Ammonium, Alkylammonium, and Amino Acid Complexes of a Hexacopper Fluoro‐Metallacrown Cavitand

Self‐Assembly of Cyclohelicate [M3L3] Triangles Over [M4L4] Squares, Despite Near‐Linear Bis‐terdentate L and Octahedral M

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Solid Versus Solution Spin Crossover and the Importance of the        Fe–N≡C(X) Angle

Solid Versus Solution Spin Crossover and the Importance of the        Fe–N≡C(X) Angle

Self‐Assembly of Cyclohelicate [M₃L₃] Triangles Over [M₄L₄] Squares, Despite Near‐Linear Bis‐terdentate L and Octahedral M