Oct 23, 2020   2:18 a.m. Alojza
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prof. Ing. Roman Boča, DrSc.
Identification number: 3291
University e-mail: qbocar [at] stuba.sk
External colleague - Faculty of Chemical and Food Technology (STU)

Supervised theses     Conferences

Basic information

Basic information about a final thesis

Type of thesis:
Dissertation thesis
Thesis title:Synthesis and magnetic properties of iron complexes
Written by (author):
Thesis supervisor:
Final thesis progress:
Final thesis was successfully defended.

Additional information

Additional information about the final thesis follows. Click on the language link to display the information in the desired language.

Language of final thesis:English

Slovak        English

Title of the thesis:
Synthesis and magnetic properties of iron complexes
Abstract Presented PhD thesis refers about synthesis, analytical investigation and magnetic study of iron complexes. The title of thesis "Synthesis and magnetic properties of iron complexes" is moreless general, but in fact a scientific effort within the PhD study was focused into three parts: 1. the spin transition iron(II) complexes with bis(pyrazol-1-yl)pyridine type of ligands; 2. the polynuclear Prussian-blue analogues with pentadentate Schiff base ligands; 3. nano- and microlithography investigations of iron(II) spin transition complex [Fe(phen)2(SCN)2]. The first part is related to family of mono- and polynuclear bis(pyrazolyl)pyridine iron(II) compounds. The series of twelve mononuclear iron(II) complexes were prepared, structurally characterised by single crystal X-ray diffraction analysis, and their magnetic properties were studied in detail. Eleven compounds exhibited the spin transition phenomenon, the twelfth compound 4(ClO4)2 was low spin. The room-temperature transition temperature exhibited six compounds: 1(ClO4)2 T1/2=333 K (60 C), 2(ClO4)2 T1/2=281 K (8 C), 5(BF4)2 T1/2=342 K (69 C), 8(ClO4)2 T1/2=289 K (16 C), 8(BF4)2 T1/2=308 K (35 C). The polymorph A of 4(BF4)2 compound possessed the room-temperature transition with a thermal hysteresis effect, T1/2up=345 K (72 C), T1/2down=337 K (64 C). The magnetic properties of three substances were successfully investigated at high-temperature regime and this investigation revealed high-temperature spin transition for 6(ClO4)2 and 6(BF4)2 compounds, and a structural phase transition for polymorph B of 4(BF4)2 compound. This part of thesis described also two polynuclear iron(II) bis(pyrazolyl)pyridine compounds (9 and 10). Mass spectroscopy investigations (ESI-ToF MS) confirmed oligomeric character of both substances. Magnetic study indicated a presence of spin transition phenomenon for these materials. The second herein reported family of compounds is a series of polynuclear Prussian-blue analogues with pentadentate Schiff base ligands. In this case, the experimental effort resulted into four heptanuclear mixed-valence compounds. Their structural characterisation was made by single crystal X-ray analysis, and variable-temperature magnetic investigation revealed a presence of the spin crossover for compound 16. Three heptanuclear complexes (17, 18 and 19) possessed a paramagnetic behaviour with a ferromagnetic exchange coupling of high-spin iron(III) coordination centres. The compound 20 -- a tetranuclear Prussian-blue complex with three paramagnetic iron(III) and one diamagnetic cobalt(III) coordination centres exhibited a solvent dependence on spin-crossover properties. The third part of Thesis was focused to investigation of spin transition compound deposited at the surfaces. The spin crossover compound [Fe(phen)2(SCN)2] was introduced on the silicon surface by MIMIC (Micro-Inject Molding In Capillaries) and LCW (Lithographically Controlled Wetting) methods. These depositions techniques allow creation of logical micro- and nanostructures, like strips and discrete dashes. The regularity of micro- and nanopatterns (thickness, length) was investigated and successfully proved by using AFM imagine technique and GIXD azimutal scan investigation found significant level of crystallinity. Moreover, the temperature variable mikro-Raman spectroscopy proved spin transition properties of [Fe(phen)2(SCN)2] patterns, what is very promissing result for utilisation of spin transition materials on the surfaces (compact discs, hard discs, screens, etc). The results of the Thesis proved the possibility of tunining the spin transition properties by variation of ligands, and in this way to prepare ambient-temperature spin transition materials, capable for technological application in case of high density memory devices, displays, molecular sensors, multifunctional surfaces etc. The Thesis extends knowledge in preparative inorganic chemistry, contributes to the forming discipline of molecular magnetism and sketches new features for chemistry of multifunctional materials.
Key words:
iron complexes, molecular magnetism, spin transition, spin crossover, N-donor ligands, magnetochemistry

Current level of public release
access to digital copies of seminar papers and theses on-line via Internet with no restrictions, incl. the right to provide sub-lincence to a third person for study, scientific, educational and information purposes.

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