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Photo-induced free ion formation in charge transfer complexes.

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Call No.	QD716.P48 F56 1998
Author	Findley, Bret
Title	Photo-induced free ion formation in charge transfer complexes.
Date	1998
Abstract	In this study we have utilized spectroscopic and photoconductivity techniques to investigate free ion formation in the fumaronitrile/trans-stilbene charge transfer-complex. We report free ion yields resulting from the direct excitation of this complex in a variety of solvents and compare our results with theory. Particularly in less polar solvents, the free ion yields we report are much larger than expected for ion pairs which are initially in contact in a relaxed solvent environment. Our results suggest that shortly after excitation, the initial separation of charges is larger than the electron donor-acceptor contact distance. Although other studies of charge transfer complexes have suggested this as well, most recent work ignores this possibility. Our work thus supports a mechanism of ion separation involving the excitation of a ground state complex into a Franck-Condon excited contact ion pair, of which at least a portion relaxes to thermalized, large-radius or loose ion pairs. These initial loose ion pairs may then diffusively separate into free ions or collapse to contact. This mechanism includes a novel speculation concerning the conversion of the Franck-Condon excited state to the initial loose ion pair. We offer suggestions as to how these species might be formed. In addition, we report the time-resolved photocurrent which results from charge transfer band excitation of the trans-stilb ene/fumaronitrile complex in toluene, fluorobenzene and tetrahydrofuran. The measured dipole moment is larger in both tetrahydrofuran (18.5 ± 1.0 D) and fluorobenzene (20.2 ± 1.0 D) than in toluene (14.2 ± 0.6 D). In tetrahydrofuran and for the first time, a transient dipole-like photocurrent is observed at short times, evolving into a steady free ion current at long times. The risetime of this photocurrent is much shorter than both the lifetime of the dipolar species and its fluorescence lifetime. These observations provide further support to the mechanism proposed.
Description	1 online resource (xi, 133 leaves) : illustrations
Format	application/pdf
Advisor	Braun, Charles L.
Subject	Electron donor-acceptor complexes. ; Complex compounds. ; Photochemistry.
College	Dartmouth College -- Department of Chemistry.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D)--Dartmouth College.
Copyright	In Copyright. This material is protected by copyright and/or related rights. You are free to use this material in any way that is permitted by copyright law that applies to your use. For other uses, you need to obtain permission from the rights-holder(s). http://rightsstatements.org/page/InC/1.0/
DOI	https://doi.org/10.1349/ddlp.2723

Title	findley1998 1
Full Text	PHOTO-INDUCED FREE ION FORMATION IN CHARGE TRANSFER COMPLEXES A Thesis Submitted to the Faculty in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry by Bret Findley DARTMOUTH COLLEGE Hanover, New Hampshire June 5, 1998 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

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