An Unusually Flexible Expanded Hexaamine Cage and Its Cu<sup>II</sup> Complexes: Variable Coordination Modes and Incomplete Encapsulation

Qin, C. Jin; James, Lloyd; Chartres, Jy D.; Alcock, Leighton J.; Davis, Kimberley J.; Willis, Anthony C.; Sargeson, Alan M.; Bernhardt, Paul V.; Ralph, Stephen F.

doi:10.1021/ic201326d

Cited by 19 publications

(15 citation statements)

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“…7 ] t r i c o s a n e (Me 8 tricosaneN 6 ), have been found to differ in this behavior and encapsulate transition metal atoms in a variety of geometries where the ligand acts as either hexadentate or pentadentate. 13,14 The chemistry of the first type of these species has shown unique physical properties, such as enhanced thermodynamic stability and extreme resistance to dissociation, which have, for instance, important applications in medicinal chemistry by complexation of 64 Cu(II) for diagnostic positron emission tomography (PET) imaging. 15 Indeed, demetalation of hexadentate cage complexes requires harsh reaction conditions such as concentrated acid, extraction of the metal with highly competitive ligands, or redox processes that liberate the metal center.…”

Section: ■ Introductionmentioning

confidence: 99%

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N₃S₃ Macrobicyclic Ligand

et al. 2013

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The macrobicyclic mixed-donor N3S3 cage ligand AMME-N3S3sar (1-methyl-8-amino-3,13,16-trithia-6,10,19-triazabicyclo[6.6.6]eicosane) can form complexes with Cu(II) in which it acts as hexadentate (N3S3) or tetradentate (N2S2) donor. These two complexes are in equilibrium that is strongly influenced by the presence of halide ions (Br(-) and Cl(-)) and the nature of the solvent (DMSO, MeCN, and H2O). In the absence of halides the hexadentate coordination mode of the ligand is preferred and the encapsulated complex ("Cu-in(2+)") is formed. Addition of halide ions in organic solvents (DMSO or MeCN) leads to the tetradentate complex ("Cu-out(+)") in a polyphasic kinetic process, but no Cu-out(+) complex is formed when the reaction is performed in water. Here we applied density functional theory calculations to study the mechanism of this interconversion as well as to understand the changes in the reactivity associated with the presence of water. Calculations were performed at the B3LYP/(SDD,6-31G**) level, in combination with continuum (MeCN) or discrete-continuum (H2O) solvent models. Our results show that formation of Cu-out(+) in organic media is exergonic and involves sequential halide-catalyzed inversion of the configuration of a N-donor of the macrocycle, rapid halide coordination, and inversion of the configuration of a S-donor. In aqueous solution the solvent is found to have an effect on both the thermodynamics and the kinetics of the reaction. Thermodynamically, the process becomes endergonic mainly due to the preferential solvation of halide ions by water, while the kinetics is influenced by formation of a network of H-bonded water molecules that surrounds the complex.

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Section: ■ Introductionmentioning

confidence: 99%

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N₃S₃ Macrobicyclic Ligand

et al. 2013

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“…The ligand 1,1,1‐tris(aminomethyl)ethane (tame) was prepared from its hydrochloride salt [16] as described [4] . The tame free base was a viscous oil as prepared.…”

Section: Methodsmentioning

confidence: 99%

Temperature and Counterion Dependent Spin Crossover in a Hexaamineiron(II) Complex

et al. 2021

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Based on previous results with [Fe(tame)2]Cl2.MeOH (tame=1,1,1‐tris(aminomethyl)ethane), which exhibits temperature dependent spin crossover, we report a series of isostructural rhombohedral salts [Fe(tame)2]X2.MeOH (X=Br−, ClO4−, BF4−) and examine their temperature dependent structures. In the case of [Fe(tame)2]Br2.MeOH, temperature dependent single crystal Vis‐NIR spectroscopy is reported as a complement to single crystal X‐ray diffraction results. The [Fe(tame)2]Br2.MeOH compound does show spin crossover behaviour but at very low temperatures (<100 K) and the spin active complex cation could not be converted exclusively to its low spin form even at 12 K. This is significantly different to its relative [Fe(tame)2]Cl2.MeOH which is entirely low spin at 60 K. The isostructural [Fe(tame)2]X2.nMeOH (X=ClO4− (n=0.5) and BF4− (n=1)) compounds show no spin crossover at the temperatures examined and remain exclusively in their high spin form. Removal of the MeOH solvent leads to another isostructural compound [Fe(tame)2](ClO4)2, which shows a remarkable reversible loss of crystallinity below 200 K that could be restored by warming to temperatures above 200 K. The fluoride and trifluoromethanesulfonate salts of [Fe(tame)2]2+ crystallise in monoclinic lattices and show no spin crossover behaviour.

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“…Compounds utilized in this study were either purchased from commercial chemical vendors and used as received (1 and 2) or synthesized according previously reported literature preparations (3)(4)(5)(6) [20][21][22][23][24].…”

Section: General Considerationsmentioning

confidence: 99%

Ligand Control of 59Co Nuclear Spin Relaxation Thermometry

et al. 2020

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Studying the correlation between temperature-driven molecular structure and nuclear spin dynamics is essential to understanding fundamental design principles for thermometric nuclear magnetic resonance spin-based probes. Herein, we study the impact of progressively encapsulating ligands on temperature-dependent 59Co T1 (spin–lattice) and T2 (spin–spin) relaxation times in a set of Co(III) complexes: K3[Co(CN)6] (1); [Co(NH3)6]Cl3 (2); [Co(en)3]Cl3 (3), en = ethylenediamine); [Co(tn)3]Cl3 (4), tn = trimethylenediamine); [Co(tame)2]Cl3 (5), tame = triaminomethylethane); and [Co(dinosar)]Cl3 (6), dinosar = dinitrosarcophagine). Measurements indicate that 59Co T1 and T2 increase with temperature for 1–6 between 10 and 60 °C, with the greatest ΔT1/ΔT and ΔT2/ΔT temperature sensitivities found for 4 and 3, 5.3(3)%T1/°C and 6(1)%T2/°C, respectively. Temperature-dependent T2* (dephasing time) analyses were also made, revealing the highest ΔT2*/ΔT sensitivities in structures of greatest encapsulation, as high as 4.64%T2*/°C for 6. Calculations of the temperature-dependent quadrupolar coupling parameter, Δe2qQ/ΔT, enable insight into the origins of the relative ΔT1/ΔT values. These results suggest tunable quadrupolar coupling interactions as novel design principles for enhancing temperature sensitivity in nuclear spin-based probes.

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An Unusually Flexible Expanded Hexaamine Cage and Its Cu^II Complexes: Variable Coordination Modes and Incomplete Encapsulation

Cited by 19 publications

References 50 publications

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N₃S₃ Macrobicyclic Ligand

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N₃S₃ Macrobicyclic Ligand

Temperature and Counterion Dependent Spin Crossover in a Hexaamineiron(II) Complex

Ligand Control of 59Co Nuclear Spin Relaxation Thermometry

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An Unusually Flexible Expanded Hexaamine Cage and Its CuII Complexes: Variable Coordination Modes and Incomplete Encapsulation

Cited by 19 publications

References 50 publications

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N3S3 Macrobicyclic Ligand

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N3S3 Macrobicyclic Ligand

Temperature and Counterion Dependent Spin Crossover in a Hexaamineiron(II) Complex

Ligand Control of 59Co Nuclear Spin Relaxation Thermometry

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An Unusually Flexible Expanded Hexaamine Cage and Its Cu^II Complexes: Variable Coordination Modes and Incomplete Encapsulation

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N₃S₃ Macrobicyclic Ligand

Computational Insights on the Geometrical Arrangements of Cu(II) with a Mixed-Donor N₃S₃ Macrobicyclic Ligand