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1. Correlating magnetic anisotropy with [Mo(CN) ₇ ] ⁴⁻ geometry of Mn ^II –Mo ^III magnetic frameworks

   https://doi.org/10.1039/c9dt02164g  

   Magott, Michał; Dunbar, Kim R.; Pinkowicz, Dawid (January 2019, Dalton Transactions)

   Four new three-dimensional (3-D) coordination frameworks based on the heptacyanomolybdate( iii ) anion were prepared and characterised by magnetic measurements: {[Mn II (imH) 2 ] 2 [Mn II (H 2 O)(imH) 3 ][Mn II (imH) 4 ] [Mo III (CN) 7 ] 2 ·6H 2 O} n ( 1 ) (imH = imidazole), {[Mn II (H 2 O) 2 (imH)] 3 [Mn II (H 2 O)(imH) 2 ][Mo III (CN) 7 ] 2 ·5H 2 O} n ( 2 ), {[Mn II (Htrz)(H 2 O) 2 ][Mn II (Htrz) 0.7 (H 2 O) 2.3 ][Mo III (CN) 7 ]·5.6H 2 O} n ( 3 ) (Htrz = 1,2,4-triazole) and {[Mn II (H 2 O) 2 ] 3 [Mn II (H 2 O) 4 ][Mo III (CN) 7 ] 2 ·6H 2 O·2urea} n ( 4 ). All four compounds exhibit long-range ferrimagnetic ordering and exhibit an opening of their magnetic hysteresis loops at 1.8 K; 1 and 2 exhibit the highest coercive fields among all known [Mo III (CN) 7 ]-based assemblies, 5000 and 4500 Oe respectively. The coercivity of 1–4 is correlated with the geometry of the heptacyanomolybdate( iii ) anion and the cyanide bridging pattern. A paramagnetic analogue of compound 1 , {[Mn II (imH) 2 ] 2 [Mn II (H 2 O)(imH) 3 ][Mn II (imH) 4 ][Re III (CN) 7 ] 2 ·6H 2 O} n ( 1Re ), where the heptacyanomolybdate( iii ) anion is substituted by the diamagnetic heptacyanorhenate( iii ) anion is also reported which constitutes the first example of a coordination framework based on [Re III (CN) 7 ] 4− . 

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2. Variability of the Conductance Changes Associated with the Change in the Spin State in Molecular Spin Crossover Complexes

   https://doi.org/10.3390/magnetochemistry9110223  

   Zaz, M Zaid; Ekanayaka, Thilini K; Cheng, Ruihua; Dowben, Peter A (November 2023, Magnetochemistry)

   Here, we examine the conductance changes associated with the change in spin state in a variety of different structures, using the example of the spin crossover complex [Fe(H2B(pz)2)2(bipy)] (pz = (pyrazol-1-yl)-borate and bipy = 2,2′-bipyridine) and [Fe(Htrz)2(trz)](BF4)] (Htrz = 1H-1,2,4-triazole) thin films. This conductance change is highly variable depending on the mechanism driving the change in spin state, the substrate, and the device geometry. Simply stated, the choice of spin crossover complex used to build a device is not the only factor in determining the change in conductance with the change in spin state. 

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3. Electronic transport properties of spin-crossover polymer plus polyaniline composites with Fe ₃ O ₄ nanoparticles

   https://doi.org/10.1088/2515-7639/ad1b35  

   Mishra, Esha; Chin, WaiKiat; McElveen, Kayleigh A.; Ekanayaka, Thilini K.; Zaz, M. Zaid; Viswan, Gauthami; Zielinski, Ruthi; N’Diaye, Alpha T.; Shapiro, David; Lai, Rebecca Y.; et al (January 2024, Journal of Physics: Materials)

   Abstract Adding Fe₃O₄nanoparticles to composites of [Fe(Htrz)₂(trz)](BF₄) spin-crossover polymer and polyaniline (PANI) drives a phase separation of both and restores the molecular structure and cooperative effects of the spin-crossover polymer without compromising the increased conductivity gained through the addition of PANI. We observe an increased on-off ratio for the DC conductivity owing to an enlarged off state resistivity and a 20 times larger AC conductivity of the on state compared with DC values. The Fe₃O₄nanoparticles, primarily confined to the [Fe(Htrz)₂(trz)](BF₄) phase, are ferromagnetically coupled to the local moment of the spin-crossover molecule suggesting the existence of an exchange interaction between both components. 

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4. Effect of different crystallographic properties on the electrical conductivity of two polymorphs of a spin crossover complex

   https://doi.org/10.1088/1361-648X/ad9a81  

   Mahbub, Rifat; McElveen, Kayleigh A; Zaz, M Zaid; Ekanayaka, Thilini K; Mishra, Esha; Bissell, Eric; Banerjee, Parag; Shapiro, David; Lai, Rebecca Y; Dowben, Peter A; et al (December 2024, Journal of Physics: Condensed Matter)

   Abstract In this study, the structure and transport properties of two polymorphs, nanoparticles and nanorods, of the iron(II) triazole [Fe(Htrz)₂(trz)](BF₄) spin crossover complex were compared. Conductive atomic force microscopy was used to map the electrical conductivity of individual nanoparticles and nanorods. The [Fe(Htrz)₂(trz)](BF₄) nanorods showed significantly higher conductivity compared to nanoparticles. This difference in electrical conductivity is partially associated to the different Fe–N bond lengths in each of the polymorphs, with an inverse relationship between Fe–N bond length and conductivity. Transport measurements were done on the nanorods for both high spin (at 380 K) and low spin (at 320 K) states under dark and illuminated conditions. The conductance is highest for the low spin state under dark conditions. In illumination, the conductance change is much diminished. 

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5. Synthesis and Characterization of [Fe(Htrz)2(trz)](BF4)] Nanocubes

   https://doi.org/10.3390/molecules27041213  

   Blanco, Alexis A.; Adams, Daniel J.; Azoulay, Jason D.; Spinu, Leonard; Wiley, John B. (February 2022, Molecules)

   Compounds that exhibit spin-crossover (SCO) type behavior have been extensively investigated due to their ability to act as molecular switches. Depending on the coordinating ligand, in this case 1H-1,2,4-triazole, and the crystallite size of the SCO compound produced, the energy requirement for the spin state transition can vary. Here, SCO [Fe(Htrz)2(trz)](BF4)] nanoparticles were synthesized using modified reverse micelle methods. Reaction conditions and reagent ratios are strictly controlled to produce nanocubes of 40–50 nm in size. Decreases in energy requirements are seen in both thermal and magnetic transitions for the smaller sized crystallites, where, compared to bulk materials, a decrease of as much as 20 °C can be seen in low to high spin state transitions. 

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