EPR and magnetic susceptibility studies of the trinuclear complex cyanuratotris[bis(.eta.5-methylcyclopentadienyl)titanium(III)], the binuclear complex uracilatobis[bis(.eta.5-methylcyclopentadienyl)titanium(III)], and related compounds

Fieselmann, B.; Hendrickson, David N.; Stucky, Galen D.

doi:10.1021/ic50185a029

Cited by 40 publications

(20 citation statements)

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“…The coordination sphere of the Ti III ions is saturated by cyclopentadienyl ligands. Interestingly, the cyanuric acid 11 bridged compounds show antiferromagnetic couplings [72], while the trithiocyanuric acid 12 bridged complexes exhibit ferromagnetic couplings [73].…”

Section: Applications Of the Spin-polarization Mechanism To Transitiomentioning

confidence: 99%

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

Glaser

Theil

Heidemeier

2008

Comptes Rendus. Chimie

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Section: Applications Of the Spin-polarization Mechanism To Transitiomentioning

confidence: 99%

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

Glaser

Theil

Heidemeier

2008

Comptes Rendus. Chimie

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“…[34][35][36][37][38][39][40] The same holds true for the C 3symmetric m 3 -bridging ligand 1,3,5-triazine, which may be regarded as the triangular extension of the m 2 -bridging ligand pyrimidine, where both ferromagnetically and antiferromagnetically coupled trinuclear Ti III complexes have been reported. [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.…”

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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“…27 For an exchange pathway involving the direct overlap of d orbitals, a decrease in the metal-metal distance generally leads to an increase in the magnitude of the antiferromagnetic interaction. 28 In a system with sizable bridging ligands, the large Ti-Ti distance prevents the direct overlap of d orbitals and necessitates a superexchange pathway. Such pathways normally result in a smaller antiferromagnetic effect than does the direct overlap pathway.…”

Section: Introductionmentioning

confidence: 99%

Electronic Structure and Magnetic Properties of Y₂Ti(μ-X)₂TiY₂ (X, YH, F, Cl, Br) Isomers

Aikens

Gordon

2002

J. Phys. Chem. A

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The electronic structure and magnetic properties of homodinuclear titanium(III) molecules with halide and hydride ligands have been studied using single-and multireference methods. Natural orbital occupation numbers suggest that the singlet states are essentially diradical in character. Dynamic electron correlation is required for calculating quantitatively accurate energy gaps between the singlet and triplet states. Isotropic interaction parameters are calculated, and three of the compounds studied are predicted to be ferromagnetic at the MRMP2/TZV(p) level of theory. Zero-field splitting parameters are determined using CASSCF and MCQDPT spin−orbit coupling with three different electron operator methods. Timings for these methods are compared. Calculated dimerization energies suggest that all dimers studied are lower in energy than the corresponding monomers. Monomer structures and vibrational frequencies are reported. Disciplines Chemistry Comments Reprinted (adapted) with permission fromThe electronic structure and magnetic properties of homodinuclear titanium(III) molecules with halide and hydride ligands have been studied using single-and multireference methods. Natural orbital occupation numbers suggest that the singlet states are essentially diradical in character. Dynamic electron correlation is required for calculating quantitatively accurate energy gaps between the singlet and triplet states. Isotropic interaction parameters are calculated, and three of the compounds studied are predicted to be ferromagnetic at the MRMP2/ TZV(p) level of theory. Zero-field splitting parameters are determined using CASSCF and MCQDPT spinorbit coupling with three different electron operator methods. Timings for these methods are compared. Calculated dimerization energies suggest that all dimers studied are lower in energy than the corresponding monomers. Monomer structures and vibrational frequencies are reported.

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EPR and magnetic susceptibility studies of the trinuclear complex cyanuratotris[bis(.eta.5-methylcyclopentadienyl)titanium(III)], the binuclear complex uracilatobis[bis(.eta.5-methylcyclopentadienyl)titanium(III)], and related compounds

Cited by 40 publications

References 10 publications

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

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

Electronic Structure and Magnetic Properties of Y₂Ti(μ-X)₂TiY₂ (X, YH, F, Cl, Br) Isomers

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EPR and magnetic susceptibility studies of the trinuclear complex cyanuratotris[bis(.eta.5-methylcyclopentadienyl)titanium(III)], the binuclear complex uracilatobis[bis(.eta.5-methylcyclopentadienyl)titanium(III)], and related compounds

Cited by 40 publications

References 10 publications

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

Spin-polarization in 1,3,5-trihydroxybenzene-bridged first-row transition metal complexes

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

Electronic Structure and Magnetic Properties of Y2Ti(μ-X)2TiY2 (X, YH, F, Cl, Br) Isomers

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Electronic Structure and Magnetic Properties of Y₂Ti(μ-X)₂TiY₂ (X, YH, F, Cl, Br) Isomers