Curiosities of the Electron Dynamics of Spin-Crossover Solids (Moessbauer)

Perchlorate salts of the ferric complexes of tridentate Schiff base ligands derived from salicylalaldehyde and N-(aminoalkyl)aziridines have been prepared and their spin-crossover properties in the solid state have been characterized using variable-temperature (4.2-313 K) magnetic susceptibility, EPR spectroscopy, and ('57)Fe Mossbauer spectroscopy. For the unperturbed complex "FeP" the low-spin (LS) (DBLHARR) high-spin (HS) spin state interconversion occurs rapidly at all temperatures, as compared to the lifetime of the ('57)Fe nuclear excited state, unlike that for most other N(,4)O(,2) complexes which flip spins slowly compared to the characteristic timescale of the Mossbauer technique. However the electron dynamics of FeP complexes are found to be highly sensitive to the nature of their solid state environs, depending on the degree of crystallinity or "defect character" as well as the presence of solvating CH(,2)Cl(,2) molecules or isostructural diamagnetic cobaltic complexes in the lattice. The defect character, as inferred from powder x-ray diffraction measurements, varies with the method of sample preparation or mechanical grinding of the solid. Introduction of defects slows down the spin state interconversion for at least some of the FeP complexes and causes incompleteness of the HS(--->)LS transformation at cryogenic temperatures. These perturbations of the electron dynamics are explained at a microscopic level in terms of the same nucleation and growth mechanism previously invoked to account for the unusual static properties of spin-crossover solids.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Federer, Wayne Douglas

• Chemistry, Inorganic

Identifier

(UMI)AAI8502137

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/70271