MnWO4, calorimetric study of the bifurcated antiferromagnetic anomaly

The heat capacity of a powdered MnWO4 sample has been measured from 5–350 K. The data show three anomalies below 20 K: a small peak at 6.8±0.1 K, then two large sharp peaks at 12.57±0.05 and 13.36±0.05 K. The magnetic entropy was measured as R ln 6. The data between 5 and 11.5 K obeys a power law dependence Cmag=ATB where B=1.73. The sharp double peak is similar to the bifurcated anomaly in MnCl2 which originates from two distinct antiferromagnetic phases, reported by R. B. Murray et al. The double anomaly is discussed in terms of the superexchange properties of MnWO4.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87559/2/445_1.pd

Thermophysical measurements on transitionmetal tungstates II. Heat capacities of antiferromagnetic nickel and cobalt tungstates,

The heat capacity of nickel tungstate (NiWO4) was measured over the temperature range 5 to 350 K by adiabatic calorimetry, and that of cobalt tungstate (CoWO4) from 5 to 550 K. Temperatures of maximum heat capacities for the antiferromagnetic anomalies in cobalt and nickel tungstates were (47.7+/-0.1) K and (59.80+/-0.05) K. Excess entropies associated with the antiferromagnetic anomalies were evaluated as R ln 2 (1.38 calth K-1 mol-1) for CoWO4 and R ln 3 (2.18 calth K-1 mol-1) for NiWO4 with the lattice heat capacities of the compounds approximated by that of ZnWO4. In addition, the heat capacity of CoWO4 showed a continuing excess heat capacity consistent with a Schottky anomaly from energy levels lying roughly 600 to 3400 calth mol-1 above the ground state. Selected thermal functions: Cpo, So, and -{Go(T)-Ho(0)}/T at 298.15 K are respectively 28.41, 30.08, and 14.01 calth K-1 mol-1 for CoWO4, and 27.77, 28.51, and 13.21 calth K-1 mol-1 for NiWO4.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21911/1/0000318.pd

Heat capacities of bis-tetraethylammonium tetrachloronickelate and tetrachlorozincate I. Structural transitions and thermophysical results

The heat capacities of bis-tetraethylammonium tetrachloronickelate () and tetrachlorozincate () were measured over the temperature range 5 to 350 K by adiabatic calorimetry. Bifurcated anomalies were found for both compounds with the temperatures of the maxima occurring at (222.1 +/- 0.1) K and (222.7 +/- 0.1) K for and at (227.9 +/- 0.2) K and (228.9 +/- 0.2) K for . The excess entropies associated with the transition regions were 9.16 and 9.96 calth K-1 mol-1 respectively. Both transition regions were characterized by equilibrium times of several days. Selected thermal functions Cpo, So, and -{Go(T) - Ho(0)}/T at 298.15 K are, respectively, 151.7, 185.33, and 92.16 calth K-1 mol-1 for and 153.0, 181.52, and 88.53 calth K-1 mol-1 for .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23707/1/0000679.pd

Thermophysical measurements on transition-metal tungstates III. Heat capacity of antiferromagnetic manganese tungstate

Three anomalies were found during measurements of the heat capacity of manganese tungstate from 4 to 350 K by adiabatic calorimetry; a small peak at (6.8 +/- 0.1) K, and two large sharp peaks at (12.57 +/- 0.05) K and (13.36 +/- 0.05) K. The excess entropy associated with the antiferromagnetic transition was estimated by means of calculations which utilized the heat capacity of zinc tungstate to approximate contributions from lattice vibrations and was found in good accord with the value R ln6. The results between 5 and 11.5 K obey a power law: Cmag = AT1.73. The double anomaly is discussed in terms of the super-exchange properties of MnWO4. Selected thermal functions, Cpo, So, and -{Go(T) - Ho(0)}/T are respectively 27.40, 31.66, and 16.10 calth K-1 mol-1 at T = 298.15 K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21919/1/0000326.pd

Satellite ligand effects on magnetic exchange in dimers. A structural, magnetic and theoretical investigation of Cu2L2X4 (L = methylisothiazolinone and X = Cl−, Br−)

Halide-bridged polymers have gained significant interest due to their diverse properties and potential applications. Stacked Cu2L2X4 dimers, where L is an organic ligand and X can be Cl− or Br−, are of interest because a chloride analogue where L = 2-pyridone, had previously been reported to exhibit bulk ferromagnetism, which augured great potentiality for this class of compounds. The synthesis, structural characterization, magnetic susceptibility measurements, and computational studies of two isostructural CuClMI (MI = methylisothiazolinone) and CuBrMI polymers of Cu(ii), along with a related CuClPYR (PYR = 2-pyridone) is reported. CuClMI and CuBrMI were found to exhibit AFM bulk properties, due to FM/AFM alternating chains along the halide-bridged polymer axis, while FM bulk properties were confirmed for CuClPYR exhibiting a FM spin ladder. In combination with a benzamide analogue, CuClBA, three O-donor amides, CuClMI, CuClBA and CuClPYR were analyzed and revealed that the kinetic exchange is affected by the identity, but more importantly, the orientation of the satellite ligands. The torsional angle of the ligand with the dimer plane is shown to significantly affect the magnetic exchange in the dimer, and between dimers, explaining the reported FM bulk properties of CuClPYR. This finding is exceedingly important, as it suggests that a spin device can be constructed to flip between singlet/triplet states by manipulating the orientation of the satellite/terminal ligand. © 2023 The Royal Society of Chemistry. This article includes supplementary data, also available for download

2-Chloro-3-fluoropyridine copper(II) complexes and the effect of structural changes on magnetic behavior

Please read abstract in the article.http://www.tandfonline.com/loi/gcoo202019-10-17hj2019Chemistr

Thermodynamics of the monohydrogen difluorides VI. Heat capacities of RbHF2 and CsHF2 from 300 to 530 K, transitions and melting

The heat capacities of RbHF2 and CsHF2 were determined from 5 to 533 K, and hence into the molten-salt region by adiabatic calorimetry. The thermodynamics of the transitions were determined. The entropy of transition [Delta]St of the II-to-I transition in RbHF2 is (5.59 +/- 0.04) calth K-1 mol-1 and the corresponding entropy of melting [Delta]Sm is (2.31 +/- 0.03) calth K-1 mol-1. Both entropy values are comparable to those in the isostructural compound KHF2. For CsHF2, [Delta]St(III-to-II), [Delta]St(II-to-I), and [Delta]Sm are (1.74 +/- 0.07), (2.20 +/- 0.08), and (1.62 +/- 0.09) calth K-1 mol-1. The occurrence of the II-to-I transition was first reported on the basis of these studies. At 500 K the standard entropies So are (47.91 +/- 0.05) and (50.63 +/- 0.05) calth K-1 mol-1 for RbHF2 and CsHF2.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22768/1/0000323.pd

Ferromagnetice exchange in bichloride bridged Cu(II) chains: magnetostructural correlations between ordered and disordered systems

The synthesis, structure, magnetic properties, and theoretical analysis of a new phase of dichloro(2-thlaro-3-methylpyridine)copper(II) (2) and its isomorphous analogue dichloro(2bromo-3-methylpyridine)copper(II) (3) are reported. Both complexes crystallize in the orthorhombic space group Pbca and present square pyramidal Cu(II) ions bridged into chains by chloride ions with each,copper(II)-bearing a single pyridine ligand. Variable temperature magnetic Susceptibility measurements were well fit by a uniform one-dimensional ferromagnetic chain model with,2) J = 69.0(7) K, C = 0.487 emu-K/mol-Oe; 3, J = 73.9(4) K, C = 0.463 emu-K/mol-Oe = Hamiltonian). The experimental J-values were confirmed-via theOretical calculations. Comparison to a known disordered polymorph of dichloro(2-chloro-3-inethylpyridine)copper(II), 1, shows marked differences as there are significant antiferromagnetic next-nearest neighbor interactions, in 1 in addition to randomness induced by the disorder which provide a distinctly different magnetic response. The differences in magnetic behavior are attributed principally to the structural difference in the Cu(II) coordination sphere, 1 being significantly closer to trigonal-bipyramidal, whose difference changes both the nearest and next-nearest neighbor interactions

The magnetic-structural relationship of [CuX6]4- [X = Cl-or Br-] perovskites containing ncarboxyalkylammonium cations of various chain lengths

Please read abstract in the article.https://onlinelibrary.wiley.com/journal/s20532733am2022Chemistr

Cobalt and zinc halide complexes of 4-chloro and 4-methylaniline : syntheses, structures and magnetic behavior

Please read abstract in the article.The Carlson School of Chemistry and Biochemistry, Clark University and the Department of Chemistry, Brandeis University. F. X. would like to acknowledge the funding from the European Union's Horizon 2020 research and innovation program under the Marie Skodowska-Curie grant agreement No 701647.http://www.elsevier.com/locate/poly2020-08-01hj2019Chemistr