1,2,4-Triazole Complexes XIV

Abstract

Heat capacity measurements on Mn(trz)2(NCS)2 in the range 1 -90 K are reported. A ?.-anomaly is found at Tc -3.292(6) K. From a comparison of the high-temperature specific heat to the predictions from series expansions the intralayer exchange constant is found to be J/k = 0.245(5) K. From the total magnetic energy involved in the transition the value J/k = -0.254(8) K is calculated. These results compare favourably with previous data from susceptibility measurements.From very recent X-ray diffraction experiments on a single crystal the space group is found to be Pbcn instead of Aba2, as was reported previously.In a recent paper [1] it was shown that the magnetic properties of Mn(l,2,4-triazole)2(NCS)2 are in good agreement with the predictions for a 2-where M is a 3d-metal, which exhibits 2-d magnetic properties [1,3,4] as is to be expected from the layered crystal structure [5,6].Very recent X-ray diffraction experiments on a single crystal of Mn(trz)2(NCS)2 indicated the space group to be Pbcn instead of Aba2, as we reported previously [1]. The axes were found asa = 8.003 (3), b -10.086(4), and c= 16.256(4) Ä. Thus the title compound is isomorphous to its Zn analogue, which also has a layered structure, very similar to that of the Co and Fe complexes [5]. This result does not affect the conclusions from the magnetic measurements. Both in Aba2 and Pbcn Mn is positioned on a two-fold axis, which must necessarily be primed. When we assume that below Tc the nuclear frame can still be described in Pbcn, the magnetic space group will be Pbcn'. From magnetic susceptibility and magnetization measurements on single crystals the intralayer exchange constant was found as J/k =0.25(1) K, while preliminary results from heat capacity measurements indicated the slightly lower value -0.23(1) K [1].In this note we present the heat capacity data on a powdered sample of Mn(trz) 2 (NCS)2. The measurements were performed in the temperature range 1-90 K, using conventional heat-pulse techniques ui Figure 1 shows the measured specific heat. From the peak the ordering temperature is found as Tc = 3.292 (6) K. Between 6 and 10 K the data could be well described by the equationwhere CL and CM denote the lattice and magnetic contributions, respectively, to the specific heat. A good fit to Eq. (1) was obtained with a = 4.2(1) X 10-3 J/K4 mole and 6 = 115(2) JK/mole.From the value of the coefficient b the exchange constant is calculated as | J\/k = 0.26(1) K, using the Heisenberg model prediction:0340-4811 I 80 / 1200-1387 $ 01.00/0. -Please order a reprint rather than making your own copy.

Lower Dimensional Magnetism

“…An interesting series of layered complexes of 1,2,4-triazole with divalent metal thiocyanates has recently been investigated by Engelfriet [130][131][132][133][134][135][136][137]. A portion of the structure of these molecules is illustrated in Fig.…”

Synthesis, Structure, Magnetic Behavior, and Mössbauer Spectroscopy of Two New Iron(II) Spin-Transition Compounds with the Ligand 4-Isopropyl-1,2,4-triazole. X-ray Structure of [Fe3(4-isopropyl-1,2,4-triazole)6(H2O)6](tosylate)6·2H2O

“…Soon after Haasnoot et al found thermochroism above room temperature in an iron(II) compound with the ligand 1 H -1,2,4-triazole (Htrz), several research groups started to investigate iron(II) compounds with (substituted)-1,2,4-triazoles ((R-)trz). − Of special interest are the 4-R-1,2,4-triazoles, for these are known to give polynuclear linear products with a triple bridge. ,, The length of these products varies from dinuclear compounds with one triple bridge, via trinuclear compounds, , to polynuclear, linear-chain products. ,,,, A two-dimensional compound with 4,4‘-bis(1,2,4-triazole) was also obtained. , A large number of these compounds show ST behavior with a variety of transition temperatures (80 K < T 1/2 < 420 K) and transition curve shapes.…”

“…Soon after Haasnoot et al 11 found thermochroism above room temperature in an iron(II) compound with the ligand 1H-1,2,4triazole (Htrz), several research groups started to investigate iron(II) compounds with (substituted)-1,2,4-triazoles ((R-)trz). [12][13][14][15][16][17][18][19][20][21] Of special interest are the 4-R-1,2,4-triazoles, for these are known to give polynuclear linear products with a triple bridge. 13,16,18 The length of these products varies from dinuclear compounds with one triple bridge, 22 pounds, 13,18 to polynuclear, linear-chain products.…”

Structure of poly-diaqua-bis(μ-4,4'-bi-1,2,4-triazole-N1,N1')-manganese(II) dinitrate dihydrate

“…This difference is significantly larger than for coordination compounds with unsubstituted 1,2,4-triazole (Engelfriet, Groeneveld & Nap, 1980, and references cited therein). This indicates a more defined localization of the double-bond character between N1--C5 and N2-C3.…”

“…In order to be able to study magnetic interactions between first-row transition-metal ions, magnetochemists need ligands which can create a [Mn(C4H4N6)2(H20)2] (NO3)2.2H20 pathway for the magnetic exchange between metal ions. During the last decade one of the ligands used for this purpose is 1,2,4-triazole (Engelfriet, Groeneveld & Nap, 1980, and references cited therein). 4-Alkylsubstituted triazoles have been studied extensively (Vos, Haasnoot, Verschoor, Reedijk & Schaminee, 1985, and references cited therein).…”