A pressure-induced displacive phase transition in Tris(ethylenediamine) Nickel(II) nitrate

Cameron, Christopher A.; Allan, David R.; Kamenev, Konstantin V.; Moggach, Stephen A.; Murrie, Mark; Parsons, Simon

doi:10.1515/zkri-2013-1688

Cited by 2 publications

(1 citation statement)

References 41 publications

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“…For crystals containing the ∆ enantiomer the low-temperature phase is P6 5 22, and P6 1 22 for those containing the Λ enantiomer. The same phase transition also occurs in [Ni(en) 3 ](NO 3 ) 2 crystals under pressure, with a transition between 0.82 and 0.87 GPa at room temperature [9]. Surprisingly, no other [M(en) 3 ](NO 3 ) 2 compounds with divalent transition metals can be found in the CSD, except for that of Cd(II), which, however, crystallizes as a racemate in the centrosymmetric space group I2/a.…”

Section: Introductionmentioning

confidence: 52%

Tris(ethylenediamine) Cobalt(II) and Manganese(II) Nitrates

et al. 2020

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Octahedral tris(ethylenediamine) coordination complexes demonstrate helicoidal chirality, due to the arrangement of the ligands around the metal core. The enantiomers of the nitrate salts [Ni(en)3](NO3)2 and [Zn(en)3](NO3)2 spontaneously resolve to form a mixture of conglomerate crystals, which present a reversible phase transition from space group P6322 to enantiomorphic P6522 or P6122, with the latter depending on the handedness of the enantiomer. We report here the synthesis and characterization of [Mn(en)3](NO3)2 and [Co(en)3](NO3)2, which are isostructural to the Zn(II) and Ni(II) derivatives. The Mn(II) analogue undergoes the same phase transition centered at 150(2) K, as determined by single-crystal X-ray diffraction, Raman spectroscopy, and differential scanning calorimetry. The Co(II) derivative does not demonstrate a phase transition down to 2 K, as evidenced by powder X-ray diffraction and heat capacity measurements. The phase transition does not impact the magnetic properties of the Ni(II) and Mn(II) analogues; these high spin compounds display Curie behavior that is consistent with S = 1 and 5/2, respectively, down to 20 K, while the temperature-dependent magnetic moment for the Co(II) compound reveals a significant orbital contribution.

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Section: Introductionmentioning

confidence: 52%

Tris(ethylenediamine) Cobalt(II) and Manganese(II) Nitrates

et al. 2020

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The curious case of proton migration under pressure in the malonic acid and 4,4′-bipyridine cocrystal

Patyk-Kaźmierczak,

Izquierdo-Ruiz,

Lobato

et al. 2024

Int Union Crystallogr J

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In the search for new active pharmaceutical ingredients, the precise control of the chemistry of cocrystals becomes essential. One crucial step within this chemistry is proton migration between cocrystal coformers to form a salt, usually anticipated by the empirical ΔpK a rule. Due to the effective role it plays in modifying intermolecular distances and interactions, pressure adds a new dimension to the ΔpK a rule. Still, this variable has been scarcely applied to induce proton-transfer reactions within these systems. In our study, high-pressure X-ray diffraction and Raman spectroscopy experiments, supported by DFT calculations, reveal modifications to the protonation states of the 4,4′-bipyridine (BIPY) and malonic acid (MA) cocrystal (BIPYMA) that allow the conversion of the cocrystal phase into ionic salt polymorphs. On compression, neutral BIPYMA and monoprotonated (BIPYH+MA−) species coexist up to 3.1 GPa, where a phase transition to a structure of P21/c symmetry occurs, induced by a double proton-transfer reaction forming BIPYH2 2+MA2−. The low-pressure C2/c phase is recovered at 2.4 GPa on decompression, leading to a 0.7 GPa hysteresis pressure range. This is one of a few studies on proton transfer in multicomponent crystals that shows how susceptible the interconversion between differently charged species is to even slight pressure changes, and how the proton transfer can be a triggering factor leading to changes in the crystal symmetry. These new data, coupled with information from previous reports on proton-transfer reactions between coformers, extend the applicability of the ΔpK a rule incorporating the pressure required to induce salt formation.

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A pressure-induced displacive phase transition in Tris(ethylenediamine) Nickel(II) nitrate

Cited by 2 publications

References 41 publications

Tris(ethylenediamine) Cobalt(II) and Manganese(II) Nitrates

Tris(ethylenediamine) Cobalt(II) and Manganese(II) Nitrates

The curious case of proton migration under pressure in the malonic acid and 4,4′-bipyridine cocrystal

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