Dissertation/Thesis Abstract

Pressure dependent magnetic investigation of tetracyanoethylene-based molecule-based magnets and their analogues
by DaSilva, Jack Guy, Ph.D., The University of Utah, 2013, 187; 3593070
Abstract (Summary)

Several metal-tetracyanoethylene (TCNE) compounds, including the [bis(pentamethylcyclopentadienyl)iron(III)][tetracyanoethylene], [FeCp*2][TCNE], family of molecule-based magnets and two cyanide based MBMs were investigated by pressure dependent DC magnetic measurements. The 0-D electron transfer salts: [FeCp*2][TCNE], ferromagnetic [FeCp*2][TCNQ] (TCNQ = 7,7,8,8-tetracyanoquinodimethane), metamagnetic [FeCp*2][TCNQ], [FeCp*2][HCBD] (HCBD = hexacyanobutadiene), and [FeCp*2][DDQ] (DDQ = 2,3-dichloro-5,6-dicyano-p-benzoquinone) exhibited an array of magnetic behavior both at ambient and applied pressure. [FeCp*2][TCNE] and [FeCp*2][HCBD] exhibited weak ferromagnetism above 4.2 and 3.1 kbar, respectively. The ferromagnetic polymorph of [FeCp*2][TCNQ] displayed linear increase to the critical temperature, Tc, and the bifurcation temperature, Tb, reaching 5.01 and 5.46 K, respectively at 10.3 kbar. The coercive field, Hcr, displayed exponential-like increase, reaching 550 Oe at 10.3 kbar. The metamagnetic polymorph of [FeCp*2][TCNQ] displayed linear increase of the Tc at low applied pressure, reaching 2.90 at 2.9 kbar, then transitioned to a paramagnetic state at further applied pressure. [FeCp*2][HCBD] transitioned from a paramagnetic state at ambient pressure to a weak ferromagnetic state at 3.1 kbar with a Tc, H cr, and Hc of 2.46 K, 25 Oe, and 2,200 Oe, respectively. The Tc and H c then increased linearly with further applied pressure to 4.80 K and 10,000 Oe, while the Hcr increased exponentially to 795 Oe, at 11.4 kbar. [FeCp*2][DDQ] exhibited paramagnetic behavior at ambient and applied pressures up to 9.2 kbar. The structurally related 2-D MnII(TCNE)I(H2O) and 3-D MnII(TCNE) 3/2(I3)1/2, showed significant increases to the Tc, Tb, and Hcr with applied pressure. A high- and low-pressure regions were observed for MnII(TCNE)I(H2O). 2-D [Ru2(O2CBu t)4][M(CN)6] ยท H2O (M = Fe, Cr) displayed suppression of hysteretic properties at high applied pressure and irreversibility of the suppression. A Mean Field (MF) analysis of three structurally related non-cubic Prussian blue analogues (PBA) was performed to assess the intensity of their coupling modes. These values were framed by the reinvestigation of several known cubic PBAs and comparing the coupling intensities, as well as evaluating the MF theory in the context of these structures as several had been evaluated by other means.

Indexing (document details)
Advisor: Miller, Joel S.
Commitee: Armentrout, Peter, Conboy, John, Molinero, Valeria, Scarpulla, Mike
School: The University of Utah
Department: Chemistry
School Location: United States -- Utah
Source: DAI-B 75/01(E), Dissertation Abstracts International
Subjects: Chemistry, Inorganic chemistry, Physical chemistry
Keywords: Cyanide, Magnet, Organic, Polymer, Pressure, Tetracyanoethylene
Publication Number: 3593070
ISBN: 978-1-303-35275-1
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