Response to steric constraint in azacryptate and related complexes of iron-(II) and -(III) *

Deeney, F.A.; Harding, Charlie; Morgan, Grace G.; McKee, Vickie; Nelson, Jane; Teat, Simon J.; Clegg, William

doi:10.1039/a801046c

Cited by 48 publications

(31 citation statements)

References 30 publications

(12 reference statements)

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“…, Fe 3+ ) gives an overall neutral charge that favors solubility in PFCs; (iii) the geometry of the chelate stabilizes the high-spin state of cations, such as S = 5/2 for Fe 3+ , which maximizes the PRE effect. 11 However, an unsubstituted SALTAME chelate (Figures 1 and 5 R 1 – R 6 = H) is insoluble in PFCs due to the simultaneous hydrophobic and lipophobic nature of all PFCs. As PFCs only dissolve highly fluorinated compounds, we sought to append perfluoroalkyl substituents to the SALTAME complex to increase fluorophilicity.…”

Section: Resultsmentioning

confidence: 99%

Fluorous-Soluble Metal Chelate for Sensitive Fluorine-19 Magnetic Resonance Imaging Nanoemulsion Probes

et al. 2018

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Fluorine-19 MRI is an emerging cellular imaging approach, enabling lucid, quantitative “hot-spot” imaging with no background signal. The utility of 19F-MRI to detect inflammation and cell therapy products in vivo could be expanded by improving the intrinsic sensitivity of the probe by molecular design. We describe a metal chelate based on a salicylidene-tris(aminomethyl)ethane core, with solubility in perfluorocarbon (PFC) oils, and a potent accelerator of the 19F longitudinal relaxation time (T1). Shortening T1 can increase the 19F image sensitivity per time and decrease the minimum number of detectable cells. We used the condensation between the tripodal ligand tris-1,1,1-(aminomethyl)ethane and salicylaldehyde to form the salicylidene-tris(aminomethyl)ethane chelating agent (SALTAME). We purified four isomers of SALTAME, elucidated structures using X-ray scattering and NMR, and identified a single isomer with high PFC solubility. Mn4+, Fe3+, Co3+, and Ga3+ cations formed stable and separable chelates with SALTAME, but only Fe3+ yielded superior T1 shortening with modest line broadening at 3 and 9.4 T. We mixed Fe3+ chelate with perfluorooctyl bromide (PFOB) to formulate a stable paramagnetic nanoemulsion imaging probe and assessed its biocompatibility in macrophages in vitro using proliferation, cytotoxicity, and phenotypic cell assays. Signal-to-noise modeling of paramagnetic PFOB shows that sensitivity enhancement of nearly 4-fold is feasible at clinical magnetic field strengths using a 19F spin-density-weighted gradient-echo pulse sequence. We demonstrate the utility of this paramagnetic nanoemulsion as an in vivo MRI probe for detecting inflammation macrophages in mice. Overall, these paramagnetic PFC compounds represent a platform for the development of sensitive 19F probes.

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Section: Resultsmentioning

confidence: 99%

Fluorous-Soluble Metal Chelate for Sensitive Fluorine-19 Magnetic Resonance Imaging Nanoemulsion Probes

et al. 2018

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“…The same is true for other metal complexes, e.g. Ga 3+ (0.62 A Ê , six-coordinate), with mean GaÐO = 1.920 A Ê and mean GaÐN = 2.131 A Ê (Liu et al, 1993), and Fe 3+ (0.785 A Ê , six-coordinate in high-spin state), with mean FeÐO = 1.944 A Ê and FeÐN = 2.150 A Ê (Deeney et al, 1998). As the ionic radius of a metal ion decreases, the MÐO and MÐN bond distances decrease.…”

Section: Figurementioning

confidence: 55%

Mononuclear nickel(II) and zinc(II) complexes with deprotonated forms of the tripodal hexadentate ligand 1,3-bis(2-hydroxybenzylidene)-2-(2-hydroxybenzylideneaminomethyl)-2-methylpropane-1,3-diamine

Yamaguchi¹,

Sunatsuki²,

Ishida³

2008

Acta Crystallogr C

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In the crystal structures of both title compounds, [1,3-bis(2-hydroxybenzylidene)-2-methyl-2-(2-oxidobenzylideneaminomethyl)propane-1,3-diamine]nickel(II) [2-(2-hydroxybenzylideneaminomethyl)-2-methyl-1,3-bis(2-oxidobenzylidene)propane-1,3-diamine]nickel(II) chloride methanol disolvate, [Ni(C(26)H(25.5)N(3)O(3))](2)Cl x 2 CH(4)O, and [1,3-bis(2-hydroxybenzylidene)-2-methyl-2-(2-oxidobenzylideneaminomethyl)propane-1,3-diamine]zinc(II) perchlorate [2-(2-hydroxybenzylideneaminomethyl)-2-methyl-1,3-bis(2-oxidobenzylidene)propane-1,3-diamine]zinc(II) methanol trisolvate, [Zn(C(26)H(25)N(3)O(3))]ClO(4) x [Zn(C(26)H(26)N(3)O(3))] x 3 CH(4)O, the 3d metal ion is in an approximately octahedral environment composed of three facially coordinated imine N atoms and three phenol O atoms. The two mononuclear units are linked by three phenol-phenolate O-H...O hydrogen bonds to form a dimeric structure. In the Ni compound, the asymmetric unit consists of one mononuclear unit, one-half of a chloride anion and a methanol solvent molecule. In the O-H...O hydrogen bonds, two H atoms are located near the centre of O...O and one H atom is disordered over two positions. The Ni(II) compound is thus formulated as [Ni(H(1.5)L)](2)Cl x 2 CH(3)OH [H(3)L is 1,3-bis(2-hydroxybenzylidene)-2-(2-hydroxybenzylideneaminomethyl)-2-methylpropane-1,3-diamine]. In the analogous Zn(II) compound, the asymmetric unit consists of two crystallographically independent mononuclear units, one perchlorate anion and three methanol solvent molecules. The mode of hydrogen bonding connecting the two mononuclear units is slightly different, and the formula can be written as [Zn(H(2)L)]ClO(4) x [Zn(HL)] x 3 CH(3)OH. In both compounds, each mononuclear unit is chiral with either a Delta or a Lambda configuration because of the screw coordination arrangement of the achiral tripodal ligand around the 3d metal ion. In the dimeric structure, molecules with Delta-Delta and Lambda-Lambda pairs co-exist in the crystal structure to form a racemic crystal. A notable difference is observed between the M-O(phenol) and M-O(phenolate) bond lengths, the former being longer than the latter. In addition, as the ionic radius of the metal ion decreases, the M-O and M-N bond distances decrease.

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“…The 1 H NMR spectrum of the complex (at room temperature) shows paramagnetically broadened signals, and the effective magnetic moment is μ eff =5.23 (RT, solid state). Compound 2 is moderately stable in the presence of air in water or methanol 21. Oxidation (as judged by the observation of a colour change) is instantaneous only in the case of the ion‐exchanged perchlorate salt, in which the sixth coordination site is most likely occupied by an aqua ligand 22.…”

Section: Resultsmentioning

confidence: 99%

On the Mechanism of the Thermal Retro‐Cycloaddition of Fulleropyrrolidines (Retro‐Prato Reaction)

Fillipone

Izquierdo

Martín‐Domenech

et al. 2008

Chemistry A European J

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Response to steric constraint in azacryptate and related complexes of iron-(II) and -(III) *

Cited by 48 publications

References 30 publications

Fluorous-Soluble Metal Chelate for Sensitive Fluorine-19 Magnetic Resonance Imaging Nanoemulsion Probes

Fluorous-Soluble Metal Chelate for Sensitive Fluorine-19 Magnetic Resonance Imaging Nanoemulsion Probes

Mononuclear nickel(II) and zinc(II) complexes with deprotonated forms of the tripodal hexadentate ligand 1,3-bis(2-hydroxybenzylidene)-2-(2-hydroxybenzylideneaminomethyl)-2-methylpropane-1,3-diamine

On the Mechanism of the Thermal Retro‐Cycloaddition of Fulleropyrrolidines (Retro‐Prato Reaction)

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