Anion driven light induced spin crossover systems towards multifunctional coordination compound
(2021)
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- Authors
- Supervisors
- Garcia, Yann
- Abstract
- In the current times, with the technologies progressing very fast, the demand to develop new materials which can offer multifunctionality and whose properties can be controlled by external stimuli is on the rise. Fe(II) spin crossover (SCO) compounds belong to one such class of advanced materials, which exhibit remarkable change in magnetic and optical properties, and are thus lauded as potential candidates for various applications including data storage and display devices. The most common approach to induce SCO has been to use temperature as external stimulus, but this is not very practical when imagining commercial applications. Alternatively, using light as trigger to induce SCO presents a fascinating option as it provides the possibility to remotely control a spin transition. In this respect, a novel methodology in which Fe(II) SCO moieties are functionalized with photo-responsive anionic organic molecules is presented thorough this thesis. Functionalization by photo-responsive anions would not only introduce additional photo-responsive properties to the Fe(II) SCO compound but could also result in a light induced SCO. We termed such phenomenon as ‘Anion driven light induced spin change’ (AD-LISC). In this context, we successfully synthesized and studied the photo-responsive anion para-sulfocinnamic acid (psca) which undergoes [2+2] photodimerization in solid state when irradiated with UV-light following Schmidt’s topochemical rules of photodimerization. Anionic psca was successfully incorporated as counter-anion in three different Fe(II) coordination compounds. The first coordination compound [Fe(3-bpp)2](psca)2·2H2O (CC-1) was based on a tridentate ligand 2,6-di(pyrazol-3-yl)pyridine (3-bpp) whose crystal structure revealed that psca molecules do not meet the Schmidt’s topochemical criteria for photodimerization in the coordination complex. Thus CC-1 was deemed as non-photoresponsive. However, CC-1 was identified as a thermal SCO compound. The second coordination compound [Fe(DMPP)2(psca)2] (CC-3) was based on a bidentate ligand, 3,5-dimethyl-1-(2'-pyridyl)-pyrazole (DMPP). In CC-3, two molecules of psca were found to be coordinated to Fe(II) centers as anionic ligands, making it a heteroleptic mononuclear complex. CC-3 remains a paramagnetic complex at all temperature range in addition to being non-photoresponsive. Finally, as third coordination compound, a 1-D Fe(II) coordination polymer [Fe(NH2trz)3](psca)2.2H2O (CP-1) based on 4-amino-1,2,4-triazole (NH2trz) ligand and psca counter anion was synthesized. CP-1 was first identified as thermal SCO compound. Upon irradiation with UV light at room temperature, CP-1 exhibited a visible color change from pink to brown. Further investigation by 57Fe Mössbauer spectroscopy revealed that high spin (HS) fraction of CP-1 increased from 30% to 53% post irradiation, hinting towards the successful realization of a partial AD-LISC at room temperature in solid state. The work presented in this thesis paves the ground work to observe AD-LISC in Fe(II) SCO compounds
- Affiliations
Citations
Kumar, V. (2021). Anion driven light induced spin crossover systems towards multifunctional coordination compound. https://hdl.handle.net/2078.5/114533