PMR and ESR of copper(II) complexes incorporating pyrazine analogs as bridging ligands

Kuramoto, Hiroyoshi; Inoue, Motomichi; Emori, Shuji; Sugiyama, Shigeru

doi:10.1016/s0020-1693(00)91663-3

Cited by 15 publications

(2 citation statements)

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“…The σ-type orbital overlaps between copper d x 2 - y 2 and nitrogen n orbitals on both sides give rise to an antiferromagnetic superexchange through the PM orbital(s) . A similar σ pathway is proposed also in copper(II)−pyrazine complexes . In sharp contrast to the copper case, complexes 1 and 2 possessing a symmetrical equatorial−equatorial coordination structure show ferromagnetic interaction through a π pathway.…”

Section: Discussionmentioning

confidence: 70%

“…18 A similar σ pathway is proposed also in copper-(II)-pyrazine complexes. 30 In sharp contrast to the copper case, complexes 1 and 2 possessing a symmetrical equatorialequatorial coordination structure show ferromagnetic interaction through a π pathway. Yamaguchi and co-workers suggested that the exchange interaction should be divided into two terms: the spin polarization effect and superexchange mechanism (spin delocalization effect).…”

Section: Discussionmentioning

confidence: 98%

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Ferromagnetic Exchange Coupling of Vanadium(IV) dπ Spins across Pyrimidine Rings: Dinuclear Complexes of Oxovanadium(IV) Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionate) Bridged by Pyrimidine Derivatives

et al. 2001

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Dinuclear oxovanadium(IV) complexes bridged by pyrimidine derivatives, L[VO(hfac)(2)](2) [L = pyrimidine (PM), 4-methylpyrimidine (MPM), 4,6-dimethylpyrimidine, 4-aminopyrimidine, and quinazoline; hfac = 1,1,1,5,5,5-hexafluoropentane-2,4-dionate], were synthesized and characterized. All of them showed intramolecular ferromagnetic interaction, and the magnetic susceptibilities were analyzed on the basis of the singlet-triplet model, giving 2J/k(B) = 2.2-5.5 K. PM[VO(hfac)(2)](2) crystallized in a monoclinic space group C2/c with a = 34.092(2), b = 6.9783(4), and c = 16.4940(9) A, beta = 109.104(1) degrees, V = 3707.8(4) A(3), and Z = 4 for C(24)H(8)F(24)N(2)O(10)V(2), and MPM[VO(hfac)(2)](2) gave isomorphous crystals. A semiempirical calculation study based on the determined structure suggests the presence of dpi-ppi interaction between vanadium and pyrimidine nitrogen atoms. Ferromagnetic coupling is explained in terms of a spin-polarization mechanism across the pyrimidine bridge. The intermolecular ferromagnetic interaction of PM[VO(hfac)(2)](2) can be interpreted by the contact between the spin-polarized pyrimidine moiety and the oxovanadium oxygen atom in an adjacent molecule.

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 98%

Ferromagnetic Exchange Coupling of Vanadium(IV) dπ Spins across Pyrimidine Rings: Dinuclear Complexes of Oxovanadium(IV) Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionate) Bridged by Pyrimidine Derivatives

et al. 2001

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Die vielseitige Chemie der 1,4‐Diazine: Organische, anorganische und biochemische Aspekte

Kaim¹

1983

Angewandte Chemie

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Das Interesse der chemischen Forschung richtet sich zunehmend auf zusammengesetzte, ,,komplexe" Systeme mit speziellen Eigenschaften und Funktionen. Als Komponenten solcher Systeme finden 1,4-Diazine wachsende Beachtung. Unter 1,4-Diazinen sollen hier Pyrazin und seine Derivate sowie Verbindungen mit Pyrazin-Teilstruktur verstanden werden; Beispiele sind Chinoxalin, Phenazin, Pteridin, Flavin und deren Derivate. Alle diese Verbindungen zeichnen sich durch ein niedrig liegendes unbesetztes n-Molekiilorbital und durch die Fahigkeit zur Briicken-Koordination aus. Die Kombination dieser beiden Eigenschaften bedingt eine spezifische Reaktivitat der 1,4-Diazine und insbesondere der Stammverbindung Pyrazin. 1,4-Diazine eignen sich ausgezeichnet fur Untersuchungen zum interund intramolekularen Elektron-Transfer bei organischen, anorganischen und biochemischen Reaktionen. Im Redoxsystem der 1,4-Diazine ist die paramagnetische 7n-Elektronen-Zwischenstufe auBerordentlich stabil, wahrend die 1,4-Dihydro-1,4-diazine mit 8 n-Elektronen im sechsgliedrigen Ring aufgrund der potentiellen Antiaromatizitat und des hohen Elektroneniiberschusses nicht generell zuganglich sind. Die inhlrente Difunktionalitat und das niedrig liegende unbesetzte Molekiilorbital des Pyrazins ermoglichen die Bildung von Koordinationspolymeren mit ungewohnlichen elektrischen und magnetischen Eigenschaften. Die an Pyrazinen beobachteten Phiinomene lassen sich schlieBlich zur Interpretation der Reaktivitat natiirlich vorkommender 1,4-Diazine heranziehen; diskutiert werden Flavine und biolumineszierende Naturstoffe. ,, Wer nur (an)organische Chemie versteht. uersteht auch fFrei Lich'enberg)azine MBt sich unterteilen in ein ,,konventionelles", das weitgehend demjenigen anderer aromatischer Heterocyclen entspricht"], und in eines, das nur bei diesem System beobachtet wird. die nicht recht."

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The Versatile Chemistry of 1,4‐Diazines: Organic, Inorganic and Biochemical Aspects

Kaim

1983

Angew. Chem. Int. Ed. Engl.

111

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In chemical research attention is increasingly being focussed on composite "complex" systems with special properties and functions. As components of such systems 1,4-diazines are steadily gaining in popularity. Here, 1,4-diazines means pyrazine and its derivatives as well as compounds with partial pyrazine structure: examples are quinoxaline, phenazine, pteridine, flavin and their derivatives. All these compounds are characterized by a low lying unoccupied n-molecular orbital and by the ability to act as bridging ligand. Due to these two properties 1,4-diazines, and especially their parent compound pyrazine, possess a characteristic reactivity. 1,4-Diazines may be employed to study inter-and intramolecular electron transfer in organic, inorganic and biochemical reactions. In the redox system of 1,4-diazines the paramagnetic 7n-electron intermediate exhibits exceptional stability, whereas the 1,4-dihydro-l,4-diazines with 8n-electrons in a six-membered ring are not generally accessible due to their potential antiaromaticity and their large excess of n electrons. Its inherent bifunctionality and the low lying unoccupied molecular orbital permit pyrazine to form coordination polymers having unusual electrical and magnetic properties. Finally, the phenomena observed for pyrazines may be used in the interpretation of the reactivity of naturally occurring 1,4-diazines, such as flavins and bioluminescent natural products.

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PMR and ESR of copper(II) complexes incorporating pyrazine analogs as bridging ligands

Cited by 15 publications

References 11 publications

Ferromagnetic Exchange Coupling of Vanadium(IV) dπ Spins across Pyrimidine Rings: Dinuclear Complexes of Oxovanadium(IV) Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionate) Bridged by Pyrimidine Derivatives

Ferromagnetic Exchange Coupling of Vanadium(IV) dπ Spins across Pyrimidine Rings: Dinuclear Complexes of Oxovanadium(IV) Bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionate) Bridged by Pyrimidine Derivatives

Die vielseitige Chemie der 1,4‐Diazine: Organische, anorganische und biochemische Aspekte

The Versatile Chemistry of 1,4‐Diazines: Organic, Inorganic and Biochemical Aspects

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