Structure and magnetic properties of one-dimensional metal complexes constructed from alternating dicyanamide linked through binuclear metal tetra-2-pyridylpyrazine subunits

Hsu, Guang-Yuan; Chen, Chin-Wang; Cheng, Sung-Chung; Lin, Shin-Huang; Wei, Ho‐Hsiang; Lee, Chin-Jhin

doi:10.1016/j.poly.2004.12.010

Cited by 39 publications

(7 citation statements)

References 48 publications

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“…In the framework of the magnetostructural studies on the metal complexes with the 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) ligand (Scheme ), − we report here the preparation, structural characterization, and variable-temperature magnetic and electron paramagnetic resonance (EPR) studies of three cobalt(II) complexes of formula [Co(tppz) 2 ](dca) 2 ( 1 ), [Co(tppz) 2 ][Co(NCS) 4 ]·MeOH ( 2 ), and [Co(tppz) 2 ][Co(NCO) 4 ]·2H 2 O ( 3 ) (dca = dicyanamide anion), where the diamagnetic organic dca group ( 1 ) and the paramagnetic metalloligands [Co(NCS) 4 ] 2– ( 2 ) and [Co(NCO) 4 ] 2– ( 3 ) act as counterions of the spin crossover unit [Co(tppz) 2 ] 2+ . The results obtained are compared to those reported for the compound [Co(tppz) 2 ](tcm) 2 (tcm = tricyanomethanide anion) from a previous communication and other related N 6 -coordinated cobalt(II) complexes (Table S1).…”

Section: Introductionmentioning

confidence: 99%

Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions

et al. 2017

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The preparation and spectroscopic and structural characterization of three cobalt(II) complexes of formulas [Co(tppz)](dca) (1), [Co(tppz)][Co(NCS)]·MeOH (2), and [Co(tppz)][Co(NCO)]·2HO (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and dca = dicyanamide] are reported here. Compounds 1-3 have in common the presence of the cationic [Co(tppz)] entity where each mer-tridentate tppz ligand coordinates to the cobalt(II) ion equatorially through two pyridyl donors and axially via the pyrazine, completing the six-coordination. The electroneutrality is achieved by the organic dca group (1) and the anionic tetrakis(thiocyanato-κN)cobaltate(II) (2) and tetrakis(cyanato-κN)cobaltate(II) (3) complexes. Direct current (dc) magnetic susceptibility measurements of 1 in the temperature range 1.9-400 K show the occurrence of a thermally induced spin crossover behavior of the [Co(tppz)] unit from a high spin (S = 3/2) at higher temperatures to a low-spin (S = 1/2) at lower temperatures, with the low spin phase being reached at T ≤ 200 K. X-band electron paramagnetic resonance (EPR) measurements in solution at low temperatures were used to characterize the low spin state. An analytical expression based on the combination of the spin-orbit coupling and both first- and second-order Zeeman effects for a d electronic configuration was used to fit the magnetic data of 1, the values of the best-fit parameters being C = 0.1367(9), λ = -168(2) cm, α = 1.12(1), Δ = 1626(15) cm, and g = 2.12(1). The magnetic behavior of the four-coordinate cobalt(II) ions [Co(NCS)] (2) and [Co(NCO)] (3) with a A ground state overlaps with the spin crossover of the [Co(tppz)] entity, the abrupt decrease of the χT product below 15.0 K being due to zero-field splitting effects between the spin components |±1/2> and |±3/2>. The combined analysis of the dc magnetic data and the Q-band EPR spectra in the solid state of 2 and 3 led to the following sets of best-fit parameters: C = 0.105(5), λ = -170(4) cm, α = 1.10(2), Δ = 1700(25) cm, g = 2.10(1), g = 2.27(1), and |D| = 3.80(2) cm (2) and C = 0.100(1), λ = -169(5) cm, α = 1.10(3), Δ = 1500(30) cm, g = 2.10(1), g = 2.28(1), and |D| = 4.30(2) cm (3). Some evidence of slowing of the relaxation of the magnetization has been found in the out-of-phase ac signal at very low temperatures under applied dc fields of 0.1-0.4 T for 3, suggesting the occurrence of single-ion magnet behavior of its [Co(NCO)] anionic entity.

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Section: Introductionmentioning

confidence: 99%

Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions

et al. 2017

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“…For related structures containing coordination compounds with the ligands tppz and dca, see: Carranza et al (2003); Hsu et al (2005). For related literature, see: Lainé et al (1995).…”

Section: Related Literaturementioning

confidence: 99%

Aqua(dicyanamido-κN¹)(nitrato-κ²O,O′)(2,3,5,6-tetra-2-pyridylpyrazine-κ³N²,N¹,N⁶)manganese(II)

et al. 2008

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In the title compound, [Mn(C2N3)(NO3)(C24H16N6)(H2O)], the central manganese(II) ion is heptacoordinated to a tridentate 2,3,5,6-tetra-2-pyridylpyrazine ligand (tppz), a bidentate nitrate ligand, a terminal monodentate dicyanamide ligand (dca) and a water molecule. The structure contains isolated neutral complexes, which are linked by O(water)—H⋯N hydrogen bonds generating chains along [010].

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“…For instance, dinuclear tppz complexes of Ni(II), Cu(II), Zn(II), Ru(II), Ru(I)/Ru(II), Ru(II)/Ru(III), Ru(I)/Pt(II), Pd(II), Cd(II), and Pt(II) have been widely reported in coordination mode (iv–g). Furthermore, a few trinuclear tppz complexes of Ni(II) and Ru(I)/Pt(II), as well as tetranuclear tppz complexes of Cu(II), Zn(II), and Rh(I) containing coordination mode (iv–g), have also been reported, together with diverse polymeric tppz complexes of Co(II), Co(II)/Mo m O n , Ni(II), Ni(II)/Mo m O n , Cu(II), Cu(II)/V x F y O z , Cu(II)/Mo m O n , Zn(II)/V m O n , and Cd(II) containing coordination mode (iv–g). In contrast, there have been very few reports of dinuclear tppz complexes in bimetallic coordination modes (iv–d) – (iv–f).…”

Section: Introductionmentioning

confidence: 99%

Structurally Diverse Polynuclear Copper(I) Complexes Bridged by Pyrimidine–, Pyrazine–, and Triazine–based Ligands with Several 2–Pyridyl Groups

et al. 2016

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The reactions of [Cu(MeCN)4]BF4 or [Cu(C2H4)n]ClO4 complexes with 4,6–bis(2–pyridyl)pyrimidine (bppym) in Me2CO under C2H4 afforded dinuclear Cu(I)–bppym/C2H4 adducts [Cu2‐(bppym)(C2H4)2](BF4)2•Me2CO (1) and [Cu2(bppym)2(C2H4)2](ClO4)2•Me2CO (2), respectively. One Cu(I) atom is coordinated by bppym and C2H4 in a distorted trigonal–planar geometry. The other Cu(I) atom is coordinated by bppym, Me2CO, and C2H4 toward a distorted tetrahedral geometry. The reaction of [Cu(MeCN)4]BF4 with 2,3–bis(2–pyridyl)pyrazine (bppz) in MeOH under C2H4 afforded a Cu(I)–bppz coordination polymer {[Cu2(bppz)2](BF4)2•MeOH}n (3). Two Cu(I) atoms are alternately bridged by two bppz to form a 1–D zigzag–chain structure. Each Cu(I) coordination sphere is largely distorted from a normal tetrahedral structure toward a square planar structure. The reaction of [Cu(MeCN)4]PF6 with 2,4,6–tris(2–pyridyl)–s–triazine (tptz) in MeEtCO under C2H4 afforded a tetranuclear Cu(I)–tptz/C2H4 adduct [Cu4(tptz)2(C2H4)2(MeCN)2](PF6)4•MeEtCO (4 b). Two Cu(I) atoms are bridged by the central triazine ring, the 2–pyridyl group, the central triazine ring, and the 2–pyridyl group in a different tptz to form a double helical structure. The other Cu(I) atom is coordinated by the central triazine ring, the 2–pyridyl group, MeCN, and C2H4 in a distorted tetrahedral geometry. The reaction of [Cu(MeCN)4]PF6 with tetra–2–pyridylpyrazine (tppz) in MeOH under C2H4 afforded a tetranuclear Cu(I)–tppz complex [Cu4(tppz)2(MeCN)4](PF6)4•MeOH (5 a). Each Cu(I) atom is coordinated by the central pyrazine ring, the 2–pyridyl group, the 2–pyridyl group in a different tppz, and MeCN in a distorted tetrahedral geometry. These four Cu(I) atoms are bridged by the two opposite tppz ligands to form a unique tetranuclear Cu(I) cage structure.

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Structure and magnetic properties of one-dimensional metal complexes constructed from alternating dicyanamide linked through binuclear metal tetra-2-pyridylpyrazine subunits

Cited by 39 publications

References 48 publications

Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions

Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions

Aqua(dicyanamido-κN¹)(nitrato-κ²O,O′)(2,3,5,6-tetra-2-pyridylpyrazine-κ³N²,N¹,N⁶)manganese(II)

Structurally Diverse Polynuclear Copper(I) Complexes Bridged by Pyrimidine–, Pyrazine–, and Triazine–based Ligands with Several 2–Pyridyl Groups

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Structure and magnetic properties of one-dimensional metal complexes constructed from alternating dicyanamide linked through binuclear metal tetra-2-pyridylpyrazine subunits

Cited by 39 publications

References 48 publications

Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions

Spin Crossover in Double Salts Containing Six- and Four-Coordinate Cobalt(II) Ions

Aqua(dicyanamido-κN1)(nitrato-κ2O,O′)(2,3,5,6-tetra-2-pyridylpyrazine-κ3N2,N1,N6)manganese(II)

Structurally Diverse Polynuclear Copper(I) Complexes Bridged by Pyrimidine–, Pyrazine–, and Triazine–based Ligands with Several 2–Pyridyl Groups

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Aqua(dicyanamido-κN¹)(nitrato-κ²O,O′)(2,3,5,6-tetra-2-pyridylpyrazine-κ³N²,N¹,N⁶)manganese(II)