The compound [Fe(abpt)2(TCNQ)2], where TCNQ is the radical anion 7,7‘,8,8‘-tetracyanoquinodimethane and abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, is an Fe(II) complex containing coordinated radical anions which undergoes a thermally induced spin-crossover with Tc = 280 K. Variable-temperature magnetic susceptibility (7−460 K) and 57Fe Mossbauer spectroscopy data give evidence for a complete S = 2 (high-spin) ↔ S = 0 (low-spin) transition, taking place gradually, without hysteresis. The X-ray structure has been determined at 298 K (1) and 100 K (2). The compound crystallizes in the triclinic space group P1 with one molecule in the unit cell of dimensions a = 9.277(2) A, b = 9.876(3) A, c = 12.272(2) A, α = 69.52(2)°, β = 86.92(2)°, and γ = 81.73(2)° for 1 and a = 9.236(2) A, b = 9.684(1) A, c = 12.137(2) A, α = 69.26(1)°, β = 87.53(2)°, and γ = 82.38(1)° for 2. Two abpt ligands coordinating via pyridyl-N1A and triazole-N1 are in the equatorial positions. Fe−N1 and Fe−N1A distances are 2.08(1) a...

Novel Hybrid Spin Systems of 7,7‘,8,8‘-Tetracyanoquinodimethane (TCNQ) Radical Anions and 4-Amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (abpt). Crystal Structure of [Fe(abpt)2(TCNQ)2] at 298 and 100 K, Mössbauer Spectroscopy, Magnetic Properties, and Infrared Spectroscopy of the Series [MII(abpt)2(TCNQ)2] (M = Mn, Fe, Co, Ni, Cu, Zn)

Influence of alkyl chain length in N-alkyl imidazoles upon the complex formation with transition-metal salts

New complexes of fullerenes C 60 and C 70 with metal dialkyldithiocarbamates, [M(R 2 dtc) x ]·[C 60 ( 70 )]·[Solvent], R = Et [M = Cu II (C 60 , 1; C 70 , 2), Cu I (C 60 , 3; C 70 , 4), Ag I (C 60 , 5), Zn II (C 60 , 6), Cd II (C 60 , 7; C 70 , 8), Hg II (C 60 , 9), Mn II (C 70 , 10)], R = Et and Me [M = Cu II (C 60 , 11), and Zn II (C 60 , 12)], and R = nPr [M = Cu II (C 60 , 13), Ni II (C 60 , 14), and Pt II (C 60 , 15)] were obtained. M(R 2 dtc) x efficiently cocrystallized with fullerene molecules as tetrahedral monomers (6, 12), dimers (1, 7, 11), and tetramers (3, 4). Fullerene molecules form closely packed hexagonal and square layers in 1, 7, and 11, hexagonal and tetragonal 3D structures in 6 and 12, and island motifs in 3 and 4. Complexes 1-15 have a neutral ground state. However, the formation of the complexes with fullerenes changes the environment of paramagnetic Cu II and Mn II . The EPR spectra of 1, 2, 11, and 13 are essentially modified relative to those of pristine Cu(R 2 dtc) 2 because of a weak coordination of Cu II to fullerene and a flattening of the central (NCS 2 ) 2 Cu fragments. Complex 10 shows a spectrum exhibiting features from 50 to 600 mT and manifests strong antiferromagnetic coupling of spins with a Weiss temperature of -96 K and the maximum of magnetic susceptibility at 46 K. Such magnetic behavior can be explained by the formation of [Mn(Et 2 dtc) 2 ] 2 dimers in 10. The illumination of the crystals of 1, 2, and 7 by white light results in up to a 10 3 increase in photocurrent. The photoconductivity spectra have maxima at 470, 450-650, and 660 nm for 1, 2, and 7, respectively. Photogeneration of free charge carriers is realized by photoexcitation of Cu(Et 2 dtc) 2 in 1 and 2, and by charge transfer from Cd(Et 2 dtc) 2 to C 60 molecules in 7. The decrease of photocurrent in 1 and 7 in a weak magnetic field with B 0 < 0.5 T was found.

Synthesis, Crystal Structures, Magnetic Properties and Photoconductivity of C60 and C70 Complexes with Metal Dialkyldithiocarbamates M(R2dtc)x, where M = CuII, CuI, AgI, ZnII, CdII, HgII, MnII, NiII, and PtII; R = Me, Et, and nPr

B. Nieuwenhuijse

Papers

Pyrazoles and imidazoles as ligands. X. electron paramagnetic resonance spectra of MnII in a tetragonal environment of four pyrazoles and two anions

Pyrazole und imidazole als liganden 10. mitt. esr-spektren von mn(ii), das tetragonal von 4 pyrazolen und zwei anionen umgeben ist