O. G. Shakirova

1A1 ⇄ 5T2 Spin Transition in New Thermochromic Iron(II) Complexes with 1,2,4-Triazole and 4-Amino-1,2,4-Triazole

New complexes of iron(II) chloride and bromide with 1,2,4-triazole (Htrz) and 4-amino-1,2,4-tri-azole (NH2trz) of composition Fe(Htrz)3Cl2 · 1.5H2O, Fe(NH2trz)3Cl2 · 2H2O, Fe(Htrz)3Br2 · 2H2O, and the Fe(NH2trz)3SO4 · H2O complex were synthesized and studied by magnetochemical, electronic, IR and Mössbauer spectroscopy methods. Magnetochemical studies showed that these complexes exhibit 1A1 ⇄ 5T2 spin transition accompanied by thermochromism (a reversible pink ⇄ white change of color).

Synthesis and crystal structure of Cu(II) complex with 4-(pyridyl-2)-1,2,4-triazole

Abstract The synthesis and X-ray structure of new Cu(II) complex with 4-(pyridyl-2)-1,2,4-triazole (pytrz) are reported. The crystal structure of [Cu3(pytrz)8(H2O)4](NO3)6 has been determined by X-ray diffraction. Crystals are triclinic, space group P-1, unit cell parameters are: a=11.971(2), b=13.079(3), c=14.439(2) A , α=114.03(1), β=97.79(1), γ=111.02(1)°, V=1819.2(6) A 3 , Z=1, Rf=0.0706. The structure consists of linear trinuclear cations with a +6 charge and six noncoordinated NO3− anions. The central copper(II) atom is located on an inversion centre and is coordinated by six nitrogen atoms of pytrz molecules bridging via the nitrogen atoms in the N 1 , N 2 positions. Each external copper(II) atom completes its coordination sphere with one monodentate pytrz via the nitrogen atom in the N1 position and two coordinated water molecules.

Spin crossover in iron(II) complexes with tris(pyrazol-1-yl)methane

Mononuclear iron(II) coordination compounds with tris(pyrazol-1-yl)methane (HC(Pz)3) described as [Fe{HC(Pz)3}2]A2 × nH2O, where A = Cl−, Br−, I−, 1/2 SO42−, n = 0–7, were synthesized. The compounds were studied by static magnetic susceptibility measurements, IR and UV/Vis spectroscopy, and powder X-ray diffraction. The crystal and molecular structures of all compounds were determined by single crystal X-ray diffraction.

High-temperature spin transition in the iron(II) trifluoromethylsulfonate, perrhenate, and tetraphenylborate complexes with tris(pyrazol-1-yl)methane

New coordination compounds of iron(II) trifluoromethylsulfonate, perrhenate, and tetraphenylborate with tris(pyrazol-1-yl)methane (HC(Pz)3) of the composition [Fe(HC(Pz)3)2]A2 (A = CF3SO3− (I), ReO4− (II), and B(C6H5)4− (III)) were synthesized and studied by the method of static magnetic susceptibility and IR and electronic spectroscopies. The crystal and molecular structures of compounds I and II were determined by X-ray diffraction analysis. The magnetochemical study of complexes I—III in the interval from 275 to 500 K showed that they possessed the high-temperature spin transition 1A1 ⇄ 5T2 accompanied by thermochromism.

Spin-crossover in complexes of iron(II) carboranes with tris(pyrazol-1-yl)methane

Synthesis procedures for coordination compounds of iron(II) 1,5,6,10-tetra(R)-7,8-dicarba-nido-undecaborates(-1) (carboranes) with tris(pyrazol-1-yl)methane (HC(pz)3) of the composition [Fe{HC(pz)3}2]A2·nH2O (A = (7,8-C2B9H12)− (I), (1,5,6,10-Br4-7,8-C2B9H8)− (II), (1,5,6,10-I4-7,8-C2B9H8)− (III), n = 0–2) are developed. The compounds are studied by static magnetic susceptibility in the temperature range of 160–500 K, electron (diffuse reflectance spectra), IR, and Mössbauer spectroscopy methods. It is shown that the complexes have high-temperature spin-crossover 1A1 ⇔ 5T2. Transition temperatures (Tc) for I–III are 370 K, 380 K, and 400 K respectively. Spin-crossover is accompanied by thermochromism (color change: pink ⇔ white).

The thermodynamic properties of Fe(II) complexes with 1,2,4-triazoles

The temperature dependences of the heat capacities at 106–330 K of the monoligand Fe(NH2trz)3I2 (I) and mixed-ligand Fe(Htrz)0.3(NH2trz)2.7SiF6 · H2O (II) complexes (Htrz is 1,2,4-triazole, and NH2trz is 4-amino-1,2,4-triazole) were studied by adiabatic vacuum calorimetry. The 1A1 ⇔ 5T2 spin transition was observed in these compounds. The thermodynamic parameters of phase transitions in I and II were determined.

Syntheses, structures, and properties of the Co(II), Ni(II), and Cu(II) complexes with 5-carboxy- and 5-methoxycarbonylpyrazoles

New cobalt(II), nickel(II), and copper(II) complexes based on 5-methoxycarbonyl-3-me-thylpyrazole (MePzCOOMe), [Co(MePzCOOMe)2(H2O)2](NO3)2 (I), [Ni(MePzCOOMe)2(H2O)2] (NO3)2 (II), and [Cu(MePzCOO)2(H2O)] · 3H2O (III), were synthesized. The compounds were studied by X-ray diffraction analysis, IR spectroscopy, and static magnetic susceptibility. The molecular and crystal structures of complexes I and III were determined by X-ray structure analysis.

Spin Crossover 1A1⇔ 5T2 in Solid Fe(trz)3x(atrz)3-3x(NO3)2·H2O (trz = 1,2,4-triazole, atrz = 4-amino-1,2,4-triazole)

AbstractThe reaction of Fe(NO3)2, trz, and atrz in ethanol–water gave solid Fe(trz)3x(atrz)3-3x(NO3)2·H2O(x = 0.1, 0.2, 0.4, 0.8). The solids were investigated by magnetic chemistry, X-ray diffraction, photoelectron (DRS), IR, and Mössbauer spectroscopy methods. The individual Fe(trz)3(NO3)2 and Fe(atrz)3(NO3)2 as well as the solid phases exhibit a reversible spin crossover 1

1A1⇔5T2 Spin Transition in Heterometallic Solid Phases FexNi1-x(Htrz)3(NO3)2 · H2O (Htrz = 1,2,4‐Triazole)

^1 A_1 \Leftrightarrow ^5 T_2