Single-crystal ESR spectra of copper(II) complexes with geometries intermediate between a square pyramid and a trigonal bipyramid

Bencini, Alessandro; Bertini, Ivano; Gatteschi, Dante; Scozzafava, A.

doi:10.1021/ic50189a047

Cited by 121 publications

(68 citation statements)

References 31 publications

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“…In contrast, Cu(PyED)·2Cl (G = 3.57) exhibits a larger distortion of the equatorial plane that is relaxed upon replacement of the axial pyridine by solvent (G = 3.86) ( Table 1). Distortion of the dihedral angle around the metal center is supported by reduced A ║ values, which denote a decrease in direct overlap between the equatorial ligand set and the Cu(II) d x 2 −y 2 SOMO (69,71,72).…”

Section: Resultsmentioning

confidence: 99%

Metal-mediated diradical tuning for DNA replication arrest via template strand scission

Porter

Lindahl

Lietzke

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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) for Cu(PyED)·2Cl, indicating three nitrogens and a chloride in the psuedo-equatorial plane with the remaining pyridine nitrogen and solvent in axial positions. EPR spectra of the Cu(II) complexes exhibit an axially elongated octahedron. This spectroscopic evidence, together with density functional theory computed geometries, suggest six-coordinate structures for Cu(II) and Fe(II) complexes and a five-coordinate environment for Zn(II) analogs. Bergman cyclization via thermal activation of these constructs yields benzannulated product indicative of diradical generation in all complexes within 3 h at 37°C. A significant metal dependence on the rate of the reaction is observed [Cu(II) > Fe(II) > Zn(II)], which is mirrored in in vitro DNA-damaging outcomes. Whereas in situ chelation of PyED leads to considerable degradation in the presence of all metals within 1 h under hyperthermia conditions, Cu(II) activation produces >50% compromised DNA within 5 min. Additionally, Cu(II) chelated PyED outcompetes DNA polymerase I to successfully inhibit template strand extension. Exposure of HeLa cells to Cu(PyBD)·SO 4 (IC 50 = 10 μM) results in a G2/M arrest compared with untreated samples, indicating significant DNA damage. These results demonstrate metal-controlled radical generation for degradation of biopolymers under physiologically relevant temperatures on short timescales. metal-mediated radicals | DNA degradation | polymerase inhibition | enediyne | Bergman cyclization

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Section: Resultsmentioning

confidence: 99%

Metal-mediated diradical tuning for DNA replication arrest via template strand scission

Porter

Lindahl

Lietzke

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…The values of g parameters and the hyperfine splitting constants A calculated from the separated EPR + [19]. Furthermore, they are typical for the "rhombic" spectrum of five-coordinate heteroligand species, with the geometry intermediate between the trigonal bipyramid and the square pyramid [29,30]. The value of the R parameter calculated for the heteroligand [Cu(Me 5 dien)(α-Ala(P))] species from the EPR spectrum (R = g y − g z /g x − g y ), being a measure of the geometry distortion from square pyramid to trigonal bipyramid and the relative contribution of the d z 2 and d x 2 −y 2 orbital in the ground state [30], is equal 1.948.…”

Section: Cumentioning

confidence: 93%

Stabilities and Coordination Modes of α-Alaninephosphonic Acid in Copper(II) Heteroligand Complexes with Ethylenediamine, Diethylenetriamine or N,N,N′,N′,N″-Pentamethyldiethylene Triamine in Aqueous Solution

et al. 2011

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− species is formed in basic solution. Our spectroscopic results indicate tetragonal geometry for the [Cu(en)(α-Ala(P))] species, geometry slightly deviated from square pyramidal for the [Cu(dien)(α-Ala(P))] complex and strongly deviated from square pyramidal towards trigonal bipyramidal for the [Cu(Me 5 dien)(α-Ala(P))] species. The coordination modes in these heteroligand complexes are discussed.

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“…For ideal tbp geometry, which for d 9 has the electronic configuration d xz,yz 4 dxy,x2-y2 4 d z 2 1 , the g values are: g || @ 2.00 < g^ @ 2.25(5). 105,106 Such an axial signal is not seen here, but the lower symmetry present in these Ni I complexes is unlikely ever to yield ideal tbp geometry.…”

Section: X-band and 35 Ghz Epr Spectra Of Mcr Red1mentioning

confidence: 64%

“…This situation is much more complicated, but has been beautifully worked out using ligand-field theory by Bencini and coworkers. 105,106 This theoretical work was in conjunction with their EPR studies on bis(N-methylsalicylaldiminato) complexes of Cu II , which quinquidentate ligand strongly favors tbp coordination geometry. Bencini et al 105,106 provided equations for the g tensor components for the entire transition from square pyramidal to tbp in C 2v symmetry.…”

Section: X-band and 35 Ghz Epr Spectra Of Mcr Red1mentioning

confidence: 97%

Overview of ligand versus metal centered redox reactions in tetraaza macrocyclic complexes of nickel with a focus on electron paramagnetic resonance studies

Telser

2010

J. Braz. Chem. Soc.

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Complexos de cobre(II) (3d 9 , S = 1/2) são estáveis e amplamente investigados por espectroscopia de ressonância paramagnética eletrônica (EPR). Já o isoeletrônico níquel(I) é muito menos comum e muito menos estudado. No entanto, níquel(I) tem interesse biológico, uma vez que o sítio ativo da metil coenzima M redutase (MCR) , S = 1/2) complexes are stable and widely investigated by electron paramagnetic resonance (EPR) spectroscopy. In contrast, isoelectronic nickel(I) is much less common and much less investigated. Nickel(I), however, is of biological interest as the active site of methyl coenzyme M reductase (MCR) contains a tetraaza macrocyclic ligand, F 430 , which coordinates Ni I in its active form, MCR red1 . As result, the redox behavior and spectroscopy of tetraaza macrocyclic complexes of nickel is of importance in biomimetic chemistry. Such efforts are complicated by the difficulty in generating Ni I from their stable, Ni II , precursors. Reduction of Ni II macrocyclic complexes can afford Ni I in certain cases, but in many other cases can lead instead to reduction of the macrocycle to generate an organic radical anion. Previous studies on the formation of tetraaza macrocyclic complexes of Ni I are discussed in terms of the competition between metal-centered and ligandcentered reduction. EPR results are particularly important in making the distinction between these two reduction processes, as formation of Ni I gives characteristic EPR spectra similar to those for Cu II , while ligand-centered reduction gives narrow EPR spectra at g = 2.00, typical of organic radicals. Even if metal-centered reduction occurs, the geometry of the resulting Ni I macrocyclic complex is highly variable and, as a result, the EPR spectral appearance is highly variable. In this case, the comparison is between the extremes of spectra typical for tetragonally distorted complexes (dx2-y2 1 ground state, which includes tetragonally distorted octahedral, square pyramidal and square planar geometries) and those for trigonal bipyramidal complexes (dz2 1 ground state). Previous work on Cu II was related to the situation for Ni I . The different types of EPR spectra for such systems are specifically discussed using previously unpublished examples of several tetraaza macrocyclic complexes of nickel, including F 430 and MCR itself.

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Single-crystal ESR spectra of copper(II) complexes with geometries intermediate between a square pyramid and a trigonal bipyramid

Cited by 121 publications

References 31 publications

Metal-mediated diradical tuning for DNA replication arrest via template strand scission

Metal-mediated diradical tuning for DNA replication arrest via template strand scission

Stabilities and Coordination Modes of α-Alaninephosphonic Acid in Copper(II) Heteroligand Complexes with Ethylenediamine, Diethylenetriamine or N,N,N′,N′,N″-Pentamethyldiethylene Triamine in Aqueous Solution

Overview of ligand versus metal centered redox reactions in tetraaza macrocyclic complexes of nickel with a focus on electron paramagnetic resonance studies

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