Synthesis and Characterization of (pyNO−)2GaCl: A Redox-Active Gallium Complex

Kirsh, Jacob M.; Woodside, Audra J.; Manor, Brian C.; Carroll, Patrick J.; Rablen, Paul R.; Graves, Christopher R.

doi:10.3390/inorganics6020050

Cited by 4 publications

(4 citation statements)

References 40 publications

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“…Even after the purge of a reductant iodide, the electron-accepting trifluoromethyl group facilitates the reduction of the nitroxide group. The redox ability of the tert-butyl pyridyl nitroxides has been well investigated [161][162][163][164][165] and actually confirmed here. Charge-transfer-triggered switching materials, like valencetautomeric cobalt(II)-SQ compounds [71][72][73] would be a next target of interest.…”

Section: Miscellaneoussupporting

confidence: 79%

“…We [74]) but very close to that of aminoxylates (1.40-1.42 Å [161][162][163][164][165]). Consequently, the present compounds can be assigned to a reduced form (i.e., phpyNO -).…”

Section: Miscellaneoussupporting

confidence: 63%

“…The N-O bond length is a fingerprint of the oxidation states of the N-O group, namely, >N + = O, >N-O•, and >N-O -. The N-O bond length in [Ni(phpyNO) 2 ] is 1.397(2) Å, and those in [Ni(phpyNO) 2 ]I 3 are 1.353(3) and 1.366(3) Å, being much longer than a typical N-O length of nitroxides (1.29 Å in a free ligand; 1.30 Å in coordination compounds[74]) but very close to that of aminoxylates (1.40-1.42 Å[161][162][163][164][165]). Consequently, the present compounds can be assigned to a reduced form (i.e., phpyNO -).The nickel(II) ion in [Ni(phpyNO) 2 ] is square planar.…”

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confidence: 97%

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Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

et al. 2021

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Heterospin systems have a great advantage in frontier orbital engineering since they utilize a wide diversity of paramagnetic chromophores and almost infinite combinations and mutual geometries. Strong exchange couplings are expected in 3d–2p heterospin compounds, where the nitroxide (aminoxyl) oxygen atom has a direct coordination bond with a nickel(II) ion. Complex formation of nickel(II) salts and tert-butyl 2-pyridyl nitroxides afforded a discrete 2p–3d–2p triad. Ferromagnetic coupling is favored when the magnetic orbitals, nickel(II) dσ and radical π*, are arranged in a strictly orthogonal fashion, namely, a planar coordination structure is characterized. In contrast, a severe twist around the coordination bond gives an orbital overlap, resulting in antiferromagnetic coupling. Non-chelatable nitroxide ligands are available for highly twisted and practically diamagnetic complexes. Here, the Ni–O–N–Csp2 torsion (dihedral) angle is supposed to be a useful metric to describe the nickel ion dislocated out of the radical π* nodal plane. Spin-transition complexes exhibited a planar coordination structure in a high-temperature phase and a nonplanar structure in a low-temperature phase. The gradual spin transition is described as a spin equilibrium obeying the van’t Hoff law. Density functional theory calculation indicates that the energy level crossing of the high- and low-spin states. The optimized structures of diamagnetic and high-spin states well agreed with the experimental large and small torsions, respectively. The novel mechanism of the present spin transition lies in the ferro-/antiferromagnetic coupling switch. The entropy-driven mechanism is plausible after combining the results of the related copper(II)-nitroxide compounds. Attention must be paid to the coupling parameter J as a variable of temperature in the magnetic analysis of such spin-transition materials. For future work, the exchange coupling may be tuned by chemical modification and external stimulus, because it has been clarified that the parameter is sensitive to the coordination structure and actually varies from 2J/kB = +400 K to −1400 K.

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Section: Miscellaneoussupporting

confidence: 79%

“…We [74]) but very close to that of aminoxylates (1.40-1.42 Å [161][162][163][164][165]). Consequently, the present compounds can be assigned to a reduced form (i.e., phpyNO -).…”

Section: Miscellaneoussupporting

confidence: 63%

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confidence: 97%

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Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

et al. 2021

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“…Evaluation of redox reaction between gallium-indium-stannum alloy and redox active species showed that Ga was more easily oxidized by losing electrons than other metals [ 22 ]. When Ga was coordinated with a redox-active ligand, it was able to regulate the electronic nature of the ligand [ 23 ]. 67 Ga (half life 78 h) and 68 Ga (half life 68 min) has been successfully used as imaging agents to assess certain types of tumors, inflammation, and other lesions [ 24 , 25 , 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Spectroscopic Study and Radical Scavenging Activity of Kaempferol Derivatives: Enhanced Water Solubility and Antioxidant Activity

Deng

Yang

Cheng

et al. 2019

IJMS

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Kaempferol (Kae) is a natural flavonoid with potent antioxidant activity, but its therapeutic use is limited by its low aqueous solubility. Here, a series of Kae derivatives were synthesized to improve Kae dissolution property in water and antioxidant activity. These compounds included sulfonated Kae (Kae-SO3), gallium (Ga) complexes with Kae (Kae-Ga) and Kae-SO3 (Kae-SO3-Ga). The compound structures were characterized by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and thermal methods (TG/DSC). The results showed that a sulfonic group (-SO3) was successfully tethered on the C3’ of Kae to form Kae-SO3. And in the metal complexation, 4-CO and 3-OH of the ligand participated in the coordination with Ga(III). The metal-to-ligand ratio 1:2 was suggested for both complexes. Interestingly, Kae-SO3-Ga was obviously superior to other compounds in terms of overcoming the poor water-solubility of free Kae, and the solubility of Kae-SO3-Ga was about 300-fold higher than that of Kae-Ga. Furthermore, the evaluation of antioxidant activities in vitro was carried out for Kae derivatives by using α,α-diphenyl-β-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) diammonium salt (ABTS) free radical scavenging. The results showed that Kae-SO3-Ga was also optimal for scavenging free radicals in a dose-dependent manner. These data demonstrate that sulfonate kaempferol-gallium complex has a promising future as a potential antioxidant and as a potential therapeutic agent for further biomedical studies.

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Boron complexes of π-extended nitroxide ligands exhibiting three-state redox processes and near-infrared-II (NIR-II) absorption properties

et al. 2022

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Synthesis and Characterization of (pyNO−)2GaCl: A Redox-Active Gallium Complex

Cited by 4 publications

References 40 publications

Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds

Synthesis, Spectroscopic Study and Radical Scavenging Activity of Kaempferol Derivatives: Enhanced Water Solubility and Antioxidant Activity

Boron complexes of π-extended nitroxide ligands exhibiting three-state redox processes and near-infrared-II (NIR-II) absorption properties

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