Magnetic properties of pyrimidine-bridged copper(II) complexes

Ishida, Takayuki; Nakayama, Kensuke; Nakagawa, Mitsutoshi; Sato, Wataru; Ishikawa, Yoshimitsu; Yasui, Masanori; Iwasaki, Fujiko; Nogami, Takashi

doi:10.1016/s0379-6779(97)80384-0

Cited by 51 publications

(29 citation statements)

References 18 publications

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“…Mitsubori et al synthesized dinuclear vanadyl complexes with variously substituted pyrimidines as bridging units and they obtained ferromagnetic interactions between the two V IV ions with coupling constants of 1e2 cm À1 [58,59]. In an extension they used these substituted pyrimidine rings for the preparation of 1D Cu II coordination polymers and they obtained again ferromagnetic couplings between the Cu II ions [60]. Lloret et al used pyrimidine for the preparation of a 2D Co II network.…”

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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“…Pyrimidine is one of the most frequently used m-phenylene bridging unit. Some complexes containing this ligand indeed exhibit ferromagnetic interactions [30][31][32][33] whereas others show antiferromagnetic interactions. [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.…”

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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“…Recently many organic coordination compounds containing transition metals as spin sources have been studied to develop magnetic interactions in organic compounds. Some copper(II) transition complexes coordinated with pyrimidines or related compounds which have meta-coordination positions showed magnetic interactions (Ishida et al, 1995(Ishida et al, , 1996(Ishida et al, , 1997. Among them, complexes of Cu II (hfac) 2 (hfac = 1,1,1,5,5,5-hexauoropentane-2,4-dionate) coordinated by quinazoline, pyrimidine and 4-methylpyrimidine showed ferromagnetic interactions at extremely low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Dipyrimidine–copper(II) dinitrate complexes showing magnetic interactions

Yasui

Ishikawa

Akiyama

et al. 2001

Acta Crystallogr Sect B

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Crystals of Cu(II)(NO(3))(2)(pm)(3) (1), and two crystalline forms of Cu(II)(NO(3))(2)(H(2)O)(2)(pm)(2), (2) and (3), showed ferromagnetic, antiferromagnetic and paramagnetic interactions at extremely low temperatures, respectively. Crystal structure analyses revealed that the complexes were catena-dinitrato[mu-pyrimidine-kappaN(1):kappaN(3)]-(pyrimidine-N(1))copper(II), [Cu(NO(3))(2)(pm)(2)](n), catena-diaquadinitrato[mu-pyrimidine-kappaN(1):kappaN(3)]copper(II), [Cu(NO(3))(2)(H(2)O)(2)(pm)](n), and diaquadinitratodipyrimidinecopper(II), Cu(NO(3))(2)(H(2)O)(2)(pm)(2) for (1), (2) and (3), respectively. In (1) the Cu atom is coordinated by the two nitrates and N atoms of the non-bridging pyrimidine and bridging pyrimidine to form a one-dimensional coordination polymer. The complex is a five-coordinated square pyramid and can be regarded as a pseudo-seven-coordinated complex, since other short non-bonding Cu.O contacts are observed. In the crystals of (2) the pyrimidine bridges the Cu atoms to form a one-dimensional coordination chain. On the other hand, complex (3) is not a coordination polymer. It is important to form a coordination polymer for the appearance of the magnetic interactions. Types of coordination of the bridging organic moieties should also play an important role in magnetic properties. Magnetic measurements of (1) and (2) show that they are good examples of uniform S = 1/2 ferro- and antiferromagnetic Heisenberg chains with exchange parameters 2J/kB = +1.8 and -36 K, respectively.

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Magnetic properties of pyrimidine-bridged copper(II) complexes

Cited by 51 publications

References 18 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

Dipyrimidine–copper(II) dinitrate complexes showing magnetic interactions

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