Electronic and magnetic metal–metal interactions in dinuclear oxomolybdenum(V) complexes across bis-phenolate bridging ligands with different spacers between the phenolate termini: ligand-centred vs. metal-centred redox activity

Bayly, Simon R.; Humphrey, Elizabeth R.; Paredes, Cecilia G.; Bell, Zöe R.; Jeffery, John C.; McCleverty, Jon A.; Ward, Michael D.; Totti, Federico; Gatteschi, Dante; Courric, Stephane; Steele, Barry R.; Screttas, Constantinos G.

doi:10.1039/b100681i

Cited by 40 publications

(12 citation statements)

References 70 publications

(93 reference statements)

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“…( E , E )-1,4-Bis(4-hydroxy)styrylbenzene (14). A 1.0 M solution of boron tribromide in dichloromethane (2.19 g, 8.73 mL, 8.73 mmol) was added dropwise to 13 (0.498 g, 1.45 mmol) in chloroform (20 mL) at 0 °C. The reaction proceeded for 1 h and was quenched with ∼30 mL of water to form a precipitate that was filtered and identified as 14 (0.31 g, 68%): mp 310−312 °C dec (lit .…”

Section: Methodsmentioning

confidence: 99%

“…As illustrated in Schemes and , bis-styrylbenzenes 7 , 9 − 13 , and 20 were obtained in yields of 58−91% using classic Wittig (Horner−Wadsworth−Emmons) couplings between benzaldehydes and the ylides derived from bisdiethylphosphonates. Bis-styrylbenzene 13 has also been obtained using Heck chemistry . Phenolic bis-styrylbenzenes 8 (97%), 14 (68%), and 21 (62%) were obtained by subsequent boron tribromide demethylation.…”

Section: Introductionmentioning

confidence: 99%

“…Bisstyrylbenzene 13 23 has also been obtained using Heck chemistry. 24 Phenolic bis-styrylbenzenes 8 (97%), 14 (68%), and 21 (62%) were obtained by subsequent boron tribromide demethylation. Finally, bis-styrylbenzene 6 was obtained in 83% yield by ester hydrolysis of 21.…”

Section: Introductionmentioning

confidence: 99%

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Polyfluorinated Bis-styrylbenzene β-Amyloid Plaque Binding Ligands

et al. 2007

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beta-Amyloid (Abeta) binding affinities and specificities for six bis-styrylbenzenes with multiple magnetically equivalent fluorine atoms in the form of a tetrafluorophenyl core or symmetrical trifluoromethyl and trifluoromethoxy groups were determined by means of fluorescence titrations with amyloid peptide Abeta1-40 and a novel in vitro fluorescence-based assay using APP/PS1 transgenic mouse brain sections. Bis-styrylbenzenes with a tetrafluorophenyl core had increased Abeta binding affinities compared to their monofluorophenyl or phenyl counterparts. Bis-styrylbenzenes with carboxylic acid functional groups had lower Abeta binding affinities than their neutral counterparts. Selected bis-styrylbenzenes were demonstrated to have good blood-brain barrier penetration capabilities. These data extend the SAR of bis-styrylbenzene Abeta binding and provide direction for the development of a noninvasive probe for early detection of Alzheimer's disease using 19F MRI.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Polyfluorinated Bis-styrylbenzene β-Amyloid Plaque Binding Ligands

et al. 2007

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“…[41,42] Ferromagnetic interactions were also achieved with a modified resorcinol ligand bridging two Fe III centers in a m-phenylene arrangement. [43,44] In a systematic study, [45] McCleverty and Ward were able to correlate the exchange coupling in dinuclear Mo complexes of extended polypyridyl [46] and polyphenol [47] ligands with the bridging topology by the spin-polarization mechanism. In particular, they observed ferromagnetic interactions in a 1,3-dihydroxy-and a 1,3,5-trihydroxybenzene-bridged Mo V complex, whereas in the 1,4-dihydroxybenzene-bridged complex they observed antiferromagnetic interactions.…”

Section: Introductionmentioning

confidence: 99%

Trinuclear Copper Complexes with Triplesalen Ligands: Geometric and Electronic Effects on Ferromagnetic Coupling via the Spin‐Polarization Mechanism

Glaser

Heidemeier

Strautmann

et al. 2007

Chemistry A European J

145

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A series of trinuclear Cu(II) complexes with the tris(tetradentate) triplesalen ligands H(6)talen, H(6)talen(tBu(2) ), and H(6)talen(NO(2) ), namely [(talen)Cu(II) (3)] (1), [(talen(tBu(2) ))Cu(II) (3)] (2), and [(talen(NO(2) ))Cu(II) (3)] (3), were synthesized and their molecular and electronic structures determined. These triplesalen ligands provide three salen-like coordination environments bridged in a meta-phenylene arrangement by a phloroglucinol backbone. The structure of [(talen)Cu(II) (3)] (1) was communicated recently. The structure of the tert-butyl derivative [(talen(tBu(2) ))Cu(II) (3)] (2) was established in three different solvates. The molecular structures of these trinuclear complexes show notable differences, the most important of which is the degree of ligand folding around the central Cu(II)-phenolate bonds. This folding is symmetric with regard to the central phloroglucinol backbone in two structures, where it gives rise to bowl-shaped overall geometries. For one solvate two trinuclear triplesalen complexes form a supramolecular disk-like arrangement, hosting two dichloromethane molecules like two pearls in an oyster. The FTIR spectra of these complexes indicate the higher effective nuclear charge of Cu(II) in comparison to the trinuclear Ni(II) complexes by the lower C--O and higher C=N stretching frequencies. The UV/Vis/NIR spectra of 1-3 reflect the stronger ligand folding in the tert-butyl complex 2 by an intense phenolate-to-Cu(II) LMCT. This absorption is absent in 1 and is obscured by the nitro chromophore in 3. The more planar molecular structures cause orthogonality of the Cu(II) d(x(2)-y(2) ) orbital and the phenolate O p(z) orbital, which leads to small LMCT dipole strengths. Whereas 1 and 3 exhibit only irreversible oxidations, 2 exhibits a reversible one-electron oxidation at +0.26 V, a reversible two-electron oxidation at +0.59 V, and a reversible one-electron oxidation at +0.81 V versus Fc(+)/Fc. The one-electron oxidized form 2(+) is strongly stabilized with respect to reference mononuclear salen-like Cu complexes. Chemical one-electron oxidation of 2 to 2(+) allows the determination of its UV/Vis/NIR spectrum, which indicates a ligand-centered oxidation that can be assigned to the central phloroglucinol unit by analogy with the trinuclear Ni triplesalen series. Delocalization of this oxidation over three Cu(II)-phenolate subunits causes the observed energetic stabilization of 2(+). Temperature-dependent magnetic susceptibility measurements reveal ferromagnetic couplings for all three trinuclear Cu(II) triplesalen complexes. The trend of the coupling constants can be rationalized by two opposing effects: 1) electron-withdrawing terminal substituents stabilize the central Cu(II)-phenolate bond, which results in a stronger coupling, and 2) ligand folding around the central Cu(II)-phenolate bond opens a bonding pathway between the magnetic Cu(II) d(x(2)-y(2) ) orbital and the phenolate O p(z) orbital, which results in a stronger coupling. Density functional calculations indicate ...

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“…[49] Unfortunately, meta-phenylene coupling units between paramagnetic transition metal ions 1) do not always guarantee ferromagnetic coupling and 2) result in much smaller coupling constants for antiferromagnetic and ferromagnetic couplings. [20,25,26,[49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66] An obvious difference of tri-Abstract: Extended phloroglucinol ligands and complexes are best described as nonaromatic heteroradialenes. Herein, the electronic structures of extended thiophloroglucinol ligands and their Ni II 3 complexes are evaluated by comparison to their phloroglucinol analogs by means of NMR, FTIR, UV/ Vis, and structural parameters.…”

Section: Introductionmentioning

confidence: 99%

Aromatic Versus Heteroradialene Character in Extended Thiophloroglucinol Ligands and their Trinuclear Nickel(II) Complexes

Feldscher¹,

Stammler²,

Bögge³

et al. 2014

Chemistry An Asian Journal

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Extended phloroglucinol ligands and complexes are best described as nonaromatic heteroradialenes. Herein, the electronic structures of extended thiophloroglucinol ligands and their Ni(II) 3 complexes are evaluated by comparison to their phloroglucinol analogs by means of NMR, FTIR, UV/Vis, and structural parameters. To provide a full set of compounds for this comparison of S versus O substitution, a new triplesalen ligand, its Ni(II) 3 complex, and a new thiophloroglucinol were synthesized. (1) H and (15) N NMR chemical shifts and coupling constants prove that the thiophloroglucinol ligands exist as the N-protonated and not the O-protonated tautomer. (13) C and (15) N NMR chemical shifts and structural parameters further demonstrated that the extended thiophloroglucinol ligands must be described with a predominant thione-enamine (heteroradialene) character despite the participation of a CS double bond. In the Ni(II) 3 complexes, this heteroradialene character is reduced but still predominant.

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Electronic and magnetic metal–metal interactions in dinuclear oxomolybdenum(V) complexes across bis-phenolate bridging ligands with different spacers between the phenolate termini: ligand-centred vs. metal-centred redox activity

Cited by 40 publications

References 70 publications

Polyfluorinated Bis-styrylbenzene β-Amyloid Plaque Binding Ligands

Polyfluorinated Bis-styrylbenzene β-Amyloid Plaque Binding Ligands

Trinuclear Copper Complexes with Triplesalen Ligands: Geometric and Electronic Effects on Ferromagnetic Coupling via the Spin‐Polarization Mechanism

Aromatic Versus Heteroradialene Character in Extended Thiophloroglucinol Ligands and their Trinuclear Nickel(II) Complexes

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