Intermolecular Magnetic Couplings in the Dinuclear Copper(II) Complex μ-Chloro-μ-[2,5-bis(2-pyridyl)-1,3,4-thiadiazole] Aqua Chlorocopper(II) Dichlorocopper(II):  Synthesis, Crystal Structure, and EPR and Magnetic Characterization

Abstract

Mu-chloro-mu-[2,5-bis(2-pyridyl)-1,3,4-thiadiazole] aqua chlorocopper(II) dichlorocopper(II) is the first characterized dimeric complex of a transition metal and this hetero ligand [C(12)H(10)Cl(4)Cu(2)N(4)OS; triclinic; space group P; a = 9.296(3) A, b = 9.933(3) A, c = 10.412(3) A; alpha = 79.054(5) degrees, beta = 82.478(6) degrees, gamma = 67.099(5) degrees; Z = 2 at room temperature]. The Cu(II) ions are bridged by the N-N thiadiazole bond and a chloride ion [Cu1-Cu2 = 3.7800(8) A]. Thermogravimetric analysis shows this structure to be stable at temperatures up to 348 K. At higher temperatures, the successive loss of a water molecule and one chloride of the dimeric unit is identified. From room temperature to 125 K, half of the Cu(2+) ions are progressively engaged in intermolecular dinuclear antiferromagnetic exchanges, while the other half remain paramagnetic. At lower temperatures, both susceptibility and electron paramagnetic resonance measurements show the paramagnetic-only couplings of this half of the Cu(2+) ions, involving a singlet ground state for interacting Cu(2+). This unusual behavior has been satisfactorily explained on the basis of intermolecular Cu-Cu interactions (J = -180 cm(-1)), involving the magnetic d(z)2 orbital perpendicular to the molecular plane, on which are seen the conjugate effects of the bridging chloride and the planar thiadiazole. It is noteworthy that the behavior of the title compound is original, compared to the systematic in-plane intramolecular antiferromagnetic coupling of other thiadiazole-containing binuclear complexes.

A first report of the complexes of 5,11,17,23-tetra-tert-butyl-25,27-diethoxycarboxymethoxy-26,28-dihydroxycalix[4]arene with Mn(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II)

“…The v m AE T continuously decreases on cooling up to 75 K and exhibits a well defined local maximum in the temperature range 75-45 K. A further decrease was observed in v m AE T up to 5 K where the value is 0.10 emu K mol À1 . The observed l eff varies from 2.28 to 0.92 BM on going from 300 to 5 K. The magnetic behaviour observed in 5 accounts for the antiferromagnetic coupling between the copper (II) centers, extending to both intra-as well as inter-molecular types as also reported in the literature [19]. The EPR spectra of Cu(II) complex, 5 shows 1,5,11,17,23-tetra-tert-butyl-25,27-diethoxycarboxymethoxy-26,28-dihydroxycalix[4]arene (p-tert-butyl-calix [4]arene-1,3-diacid, H 4 L); [R = tert-butyl].…”

Structural characterisation of [Cu2(bptd) (H2O) Cl4] and [Ni2(bptd)2(H2O)4] Cl4·3H2O; evidence of null intramolecular exchanges by EPR and magnetic measurements

“…The Cu 2þ and Ni 2þ coordination polyhedra are given in Table 1. It is noticeable that the xT product was satisfactorily fitted using the sum of the Cu(2) paramagnetic contribution and the Cu(1)…Cu(1) 0 Bleaney -Bowers equation for intermolecular couplings [15].…”

“…ESR study was achieved using a 2D four pulse HYSCORE sequence as detailed in Ref. [15] about the previous [Cu 2 (bptd) (H 2 O) Cl 4 ] characterization.…”

Crystal structure of bis(azido-κN)bis[2,5-bis(pyridin-2-yl)-1,3,4-thiadiazole-κ2N2,N3]cobalt(II)

“…An interesting feature of the metal-ligand chemistry of these compounds is that the resulting complexes can be mononuclear (Bentiss et al, 2011a;2012;Kaase et al, 2014) or binuclear (Bentiss et al, 2004;Laachir et al, 2013). Another preparation method involves the use of the organic ligand and pseudohalide ions, especially the azide ion which is known to exhibit different coordination modes (Nath & Baruah, 2012;Ray et al, 2011).…”