Ferromagnetism in an Extended Three-Dimensional, Diamond-like Copper(II) Network: A New Copper(II)/1-Hydroxybenzotriazolato Complex Exhibiting Soft-Magnet Properties and Two Transitions at 6.4 and 4.4 K

Abstract

The use of the substituted benzotriazole ligand btaOH (1-hydroxybenzotriazole) in copper(II) chemistry has yielded a structurally and magnetically very interesting complex. The [Cu2(O2CMe)4(H2O)2]/btaOH.H2O/aqueous NH3 (1:4:4, 1:3:3, 1:2:2) reaction system in MeOH gives dark brown-green [Cu(btaO)2(MeOH)]n (4) in approximately 80% yield. 4 crystallizes in the tetragonal space group P4(3)2(1)2 with (at 25 degrees C) a = 9.915(1) A, b = 9.915(1) A, c = 14.715(2) A, and Z = 4. The structure consists of a 3D, diamond-like copper(II) lattice. The CuII atom has a square pyramidal geometry with four btaO- ligands at the basal plane. The btaO- ion functions as a bidentate bridging ligand, with N(3) and the deprotonated oxygen being the ligating atoms. Dc and ac magnetic susceptibility measurements, together with low-field (10 G) and high-field (up to 5000 G) magnetization data, are consistent with ferromagnetic interactions on the scale of the crystal lattice with two critical temperatures: 6.4 and 4.4 K. The former critical temperature could correspond to a transition from a paramagnetic to a ferromagnetic state; the latter one, to a transition from a ferromagnetically ordered state to its 3D ordering. The magnetic data, along with the field dependence of the magnetization and the EPR data, are also in line with a soft magnet. Moreover, the EPR studies performed on 4 reveal unique features reported for the first time in the field of molecular magnetism.

The “periodic table” of benzotriazoles: Uranium(VI) complexes

“…Crystallographic data for 1, 2, 3 and 4 · diMebtaH · MeCN have been deposited with the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax + 44 1223 336 033; e-mail: Table S2, thin cyan lines), extended parallel to the [1][2][3][4][5][6][7][8][9][10] crystallographic direction in the crystal structure of complex 2. b) The U2-containing molecules form chains through intermolecular π-π (dark green lines) and "non-classical" H-bonding interactions (C13-H13⋯O6, Table S2, thin cyan lines), extended parallel to the b axis. These chains cross each other at points above and below the 6MebtaH ligands creating the 3D structure shown in c and resulting in stacks of ligands presented in d. Light green, yellow and dark green thick lines indicate the three different types of π-π overlaps in the structure of the complex, shown in e, f and g, respectively, with the corresponding distances and angles between the planes being 3.50 Å and 0°(e), 3.37 Å and 5.5°(f), and 3.44 Å and 0°(g).…”

“…Over the last 30 years or so, we [1][2][3][4][5][6][7][8] and other groups [8][9][10][11][12][13][14][15][16][17] have been exploring the coordination chemistry of benzotriazoles. Research in this area ranges from efforts to model the corrosion inhibition of some metals (particularly Cu and its alloys) by benzotriazoles [18], to the synthesis of benzotriazolato coordination clusters [2,[4][5][6][7]9,11,13,15] and polymers [1,3,12,14,16,17] with esthetically pleasing structures and exciting physical properties. Although the use of this family of ligands has been investigated widely in 3d- [1-11, 13-15,17] and 4f-metal [12,16] chemistry, their employment in the chemistry of 5f-metal ions has completely been ignored.…”

“…S9-S11) of the uranyl complexes 1, 2 and 4 · diMebtaH · MeCN in d 6 -DMSO reveal that these compounds decompose in solution to release the benzotriazole ligand; the spectra of the complexes are identical with those of the corresponding free ligands Mebta, 5MebtaH and diMebtaH, respectively. For example, the spectrum of 1 shows a sharp singlet at δ 4.30, a triplet at δ 7.39, a triplet at δ 7.55, a doublet at δ 7.83 and a doublet at δ 8.01 ppm, with relative [1,2,3]triazole or simply benzotriazole (btaH; R_R΄_R΄΄_H). R, R΄ and R΄΄ can be non-donor (Me, Cl, NO 2 ,…) or donor (OH, COOH, CH 2 OH, CH 2 COOH,…) groups.…”

The succinamate(−1) ligand in 4f-metal chemistry: First example of amide coordination in the double-chain 1D coordination polymer catena-aquatris(succinamato(−1))erbium(III)

“…Herein, we consider these three questions: the answer is of wider interest because the resulting structure suggests future routes to obtain coordination polymers employing anionic monoamides of a,x-dicarboxylates as ligands. The present work can be considered as continuation of our research efforts on 3d-and 4f-metal coordination polymers [15,17] …”

Hexakis(1-oxido-1H-benzotriazol-3-ium-κO)iron(III) tris(perchlorate) acetonitrile disolvate

“…Comment 1-Hydroxybenzotriazole with a substituted donor group on the azole ring has recently been used to synthesize polymeric and polynuclear coordination complexes (Tangoulis et al, 2000;Papaefstathiou et al, 2002;. There are three potential donor atoms in 1-hydroxybenzotriazole, resulting in coordination flexibility.…”