Effect of Pressure on Intramolecular Charge-Transfer and Spin-Crossover Materials

Hammack, William Scott

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Description

Title

Effect of Pressure on Intramolecular Charge-Transfer and Spin-Crossover Materials

Author(s)

Hammack, William Scott

Issue Date

1988

Doctoral Committee Chair(s)

Drickamer, Harry G.,

Department of Study

Chemical Engineering

Discipline

Chemical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Engineering, Chemical

Abstract

• In this work we consider two classes of materials, namely (1) materials that exhibit an intramolecular electron transfer (IET) and (2) materials that can exist in either a high- or a low-spin electronic configuration. These materials are studied as crystalline solids, doped into polymers, and in solution. In general there are two aspects we consider: (1) in what way does pressure affect the electronic structure of these two classes of materials and (2) what is the relationship between bulk and local (or molecular) properties in these types of materials. The IET materials studied take a variety of forms: between two transition metal moieties (a mixed-valence molecular), in an organic charge-transfer complex, and in an inorganic-organic donor-acceptor complex.
• The major results are (1) that with pressure, the high-spin complex (Fe(6-Me-py)$\sb3$tren) (ClO$\sb4$)$\sb2$ will convert to a low-spin electronic ground state in acetone and dichloromethane solutions in a pressure range of 10.0 kbar; (2) with pressure we can control the degree of electronic coupling and the energy required to photo-induce an electron transfer in the (Cl$\sb5\cdot$5H$\sb2$O) salt of the Creutz-Taube mixed valence ion and in the (Fe(CN)$\sb6$) $\sp{4-}\cdot$DMV$\sp{2+}$ ion pair; (3) the peak maxima of the charge-transfer bands of a series of pyridinium-N-phenoxide betaine dyes in alcoholic and polymeric solvents correlate well with the quantity (D$\sb{\rm s}$ $-$ 1)/(D$\sb{\rm s}$ + 2), where D$\sb{\rm s}$ is the static dielectric constant of the solvents; and (4) the position of the intervalence electronic absorption band of a binuclear mixed-valence ion in solution does not correlate with the quantity (1/n$\sp2$ $-$ 1/D$\sb{\rm s}$) as predicted by the Marcus continuum model for the solvent reorganizational energy. Results (1) and (2) above are examples of the use of pressure to change the electronic structure of a material, while results (3) and (4) show how pressure can be used to vary the bulk properties of a material, either continuously or discontinuously, and thereby determine the relationship between the bulk and local properties of a material.

Graduation Semester

1988

Type of Resource

text

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