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Photomagnetism and Multifunctionality in Spin-Crossover Fe(II) Complexes and Sigma-Dimer of Organic Radicals

Title: Photomagnetism and Multifunctionality in Spin-Crossover Fe(II) Complexes and Sigma-Dimer of Organic Radicals.
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Name(s): Van Phan, Hoa, author
Shatruk, Mykhailo, professor directing dissertation
Chiorescu, Irinel, university representative
Alabugin, Igor V., committee member
Strouse, Geoffrey F., committee member
Florida State University, degree granting institution
College of Arts and Sciences, degree granting college
Department of Chemistry and Biochemistry, degree granting department
Type of Resource: text
Genre: Text
Issuance: monographic
Date Issued: 2014
Publisher: Florida State University
Place of Publication: Tallahassee, Florida
Physical Form: computer
online resource
Extent: 1 online resource (157 pages)
Language(s): English
Abstract/Description: Trapping of a photoinduced metastable paramagnetic state of a molecular material is one of the most fascinating phenomena of molecular bistability, due to its potential uses in memory devices, sensors, or radiation detectors. This thesis focuses on two photomagnetic systems that are very different but show conceptual similarity - spin-crossover (SCO) complexes and sigma-dimers of organic radicals. Despite the long history of research on SCO in complexes of 3d⁴-3d⁷ transition metal ions, the design and preparation of SCO complexes for surface functionalization, the prediction of spin state behavior, and the combination of SCO with other properties, such as conductivity or ferroelectricity, in a single material are current emerging areas associated with many challenges. In this thesis, we demonstrate that 2,2′-biimidazole offers a convenient platform for modification of SCO complexes for surface functionalization. The ligand can be conveniently alkylated at the protonated nitrogen atoms, preserving essentially the same ligand filed strength. We suggest a simple approach to predicting the spin state of tris-homoleptic diimine complexes with the Fe(II) ion. We also show an effective way to incorporate TCNQ*[superscript δ]⁻ organic radical as the conducting moieties into SCO complexes. These complexes offer a rare example of highly conducting photomagnets. The light-induced magnetism has been studied extensively in spin crossover coordination compounds and charge transfer complexes. Prior to the present work, however, no such studies existed on organic systems in solid state form. Here we demonstratefor the first time the photoinduced splitting of hypervalent 4-center 6-electron S***S−S***S bridged σ-dimers of bisdithiazolyl radicals, 8-fluoro-4-ethyl-4H-bis[1,2,3]dithiazolo[4,5-β: 5',4'-e]pyridin-3-yl, β-dimer phase (β-FBPEt) and 8-fluoro-4-methyl-4H-bis[1,2,3]dithiazolo[4,5-β: 5',4'-e]pyridin-3-yl, (β-FBPMe). The results are very encouraging, as we have been able to generate the S=1/2 radical forms of these materials under irradiation. Moreover, these radicals exhibit an unprecedented stabilty in the solid state; one of them convert back to the diamagnetic σ-dimer (S=0) at the temperature as high as 242 K. The dimer-to-radical photoconversion, which we dubbed the LIRT (light-induced radical trapping) effect, has been demonstrated by magnetic susceptibility measurements, optical spectroscopy, and single crystal X-ray diffraction.
Identifier: FSU_migr_etd-9232 (IID)
Submitted Note: A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
Degree Awarded: Fall Semester, 2014.
Date of Defense: October 31, 2014.
Keywords: conductivity, LIESST, LIRT, photomagnetism, radical, spin crossover
Bibliography Note: Includes bibliographical references.
Advisory Committee: Michael Shatruk, Professor Directing Dissertation; Irinel Chiorescu, University Representative; Igor Alabugin, Committee Member; Geoffrey F. Strouse, Committee Member.
Subject(s): Chemistry
Persistent Link to This Record: http://purl.flvc.org/fsu/fd/FSU_migr_etd-9232
Owner Institution: FSU

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Van Phan, H. (2014). Photomagnetism and Multifunctionality in Spin-Crossover Fe(II) Complexes and Sigma-Dimer of Organic Radicals. Retrieved from http://purl.flvc.org/fsu/fd/FSU_migr_etd-9232