Coordinative Versatility of Guanazole [3,5‐Diamino‐1,2,4‐triazole]: Synthesis, Crystal Structure, EPR, and Magnetic Properties of a Dinuclear and a Linear Trinuclear Copper(II) Complex Containing Small Bridges and Triazole Ligands

Abstract

New complexes with guanazole (3,5‐diamino‐1,2,4‐triazole = Hdatrz), [Cu2(Hdatrz)2(μ‐OH2)(H2O)4(SO4)](SO4)·3.5H2O (1) and [Cu3(Hdatrz)4(μ‐Cl)2(H2O)4(SO4)2]·11.4H2O (2), have been prepared and structurally characterized. Complex 1 is a noncentrosymmetric dinuclear compound in which the copper(II) ions are bridged by two triazole ligands and one μ‐OH2 molecule, with a Cu(1)···Cu(2) distance of 3.4945(8) Å. The chromophores are Cu(1)N2O2O′ (square pyramidal), and Cu(2)N2O2O′O″ (octahedral). Complex 2 has a linear trinuclear copper(II) structure, with two crystallographically independent copper(II) atoms. Neighboring copper(II) ions are linked by two triazole ligands and one slightly asymmetric chlorido bridge. The intratrimeric Cu(1)···Cu(2) distance is 3.5602 (4) Å. Cu(2), the central copper, is coordinated to N4Cl2 (octahedral) while Cu(1), the terminal copper, is coordinated to N2O2ClO′ (also octahedral). Magnetic susceptibility measurements (2–300 K) are in accordance with the dinuclear (1) and trinuclear (2) nature of these compounds. The best‐fit parameters, obtained with the Hamiltonian H =–JΣi<jSiSj, are as follows: g = 2.10(1) and J = –94.3(2) cm–1 for 1; and gcentral = 2.12(1), gperipheral = 2.07(1), and J =–89.9(3) cm–1 for 2. Compound 1, which has an unprecedented folded bridging {Cu(N–N)2Cu} system, exhibits a magnetic exchange comparable to that of related planar compounds. Comparison of the magneto‐structural properties of 2 with those of analogous linear trinuclear compounds has made a first approach to the relative magnitude of the J value possible. The Q‐band powder spectra, which were recorded in a range from 4 K to room temperature, are in agreement with the magnetic susceptibility measurements. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Bis‐μ‐pyrazolate‐Bridged Dinickel(II) and Dicopper(II) Complexes: An Example of Stereoelectronic Preference of Metal Ions and Stabilization of Mixed‐Valence NiIIINiII Species

“…R = 1.84 ϫ 10 -7 for 2. The magnitude of the exchange interaction is similar to that observed for other bis(µ-pyrazolate)-bridged [28,29] and the related bis(µ-N 1 ,N 2 )triazolebridged [33] dinuclear Cu II complexes. Solution-state µ eff /Cu value for 2 at 298 K is 1.4 µ B , slightly lower than that obtained as a solid.…”

A novel hydroxo-bridged cyclic tetranuclear copper(II) complex using the guanazole ligand: Synthesis, crystal structure and thermal analysis

“…In the cyclic tetranuclear complex 1, the combination of l-OH and single-l-N1,N2-guanazole bridges gives rise to a significantly shorter Cu1Á Á ÁCu2 [3.3550(4) Å] and Cu3Á Á ÁCu4 [3.3611(4) Å] separation distances than that of only singly bridged l-N1,N2-guanazole Cu1Á Á ÁCu4 [3.5955(4) Å] and Cu2ÁÁÁCu3 [3.5198(4) Å] distances, indicating that the l-OH bridges cause the bridging system to fold. The Cu1Á Á ÁCu2 and Cu3Á Á ÁCu4 distances in 1 are even shorter than the earlier reported double-l-N1,N2-guanazole bridged copper(II) linear dinuclear and trinuclear species with additional l-OH 2 and chloro bridges [15], where the CuÁ Á ÁCu separations are 3.4945(8) and 3.5602(4) Å, respectively. Such CuÁ Á ÁCu distances are close to the Cu1Á Á ÁCu4 and Cu2Á Á ÁCu3 separation seen in 1.…”

“…A wide range of copper(II) triazole complexes have been reported, which include dinuclear, linear trinuclear, trinuclear triangular, one-dimensional chain, two-dimensional networks and hexanuclear rings [2,[10][11][12][13][14][15], but cyclic tetranuclear copper(II) complexes with triazole ligands still remain relatively unexplored [5]. In a literature survey, we found that although there are many tetranuclear pyrazole complexes, analogous tetranuclear triazole complexes are rare [16].…”

3,5-Diamino-4H-1,2,4-triazol-1-ium 4-nitrobenzoate dihydrate

“…Guanazole (3,5-diamino-1,2,4-triazole) derivatives, attract an interest and are actively studied as ligands in the synthesis of d-metal complexes (Aznar et al, 2006), precursors of condensed N-heterocyclic systems (Fernandes et al, 2015), corrosion inhibitors (El Issami et al, 2007;Kuznetsov & Kazansky, 2008), biologically active compounds with a wide range efficiency (Chohan et al, 2010) and as high-energy compounds (Kofman, 2002). The present work report the synthesis and crystal structure of the title compound (Fig.…”