Date of Award:

5-1983

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Chemistry and Biochemistry

Committee Chair(s)

William M. Moore (Committee Chair)

Committee

William M. Moore

Committee

Karen W. Morse

Abstract

This research has focused on the sensitized photoisomerization step of a solar energy storage system based on the interconversion of norbornadiene (NBD) and quadricyclane (Q). Sensitizers studied in the photoisomerization were arylphosphine complexes of copper(I) halides [(Ph3P)3CuX, (MePh2P)3CuX, (DIPHOS)CuCl; X = Cl, Br, I and DIPHOS = Ph2P(CH2)2PPh2]. The lowest electronic excited state of the complexes can be an effective triplet energy sensitizer as evidenced by a maximum quantum yield of 1.0 with (MePh2P)3CuX. The sensitization mechanism of the L3CuX complexes is proposed as a bimolecular energy transfer process in which energy transfer takes place through the metal centered orbitals. The efficiency of the (MePh2P)3CuX sensitizers is unprecedented by other reported inorganic or organic sensitizers; however, ligand dissociation of the complexes in dilute solutions detracts from their otherwise attractive features. The free ligands undergo rapid photodecomposition and are extremely poor sensitizers of the NBD/Q system. The ligand dissociation of the LmCunCln (L = Ph3P, MePh2P; m:n = 3:1, 2:1, 4:2, 3:2, 2:2) complexes was modeled by use of vapor pressure osmometry and UV absorption. The equilibria and equilibrium constants of dissociation were determined for benzene solutions at 37 °C. The stability of the LmCunCln complexes (Ph3P<2P) toward ligand dissociation is attributed to the larger steric requirements of Ph3P in comparison to MePh2P. Evidence for ground state complexation of NBD and the LmCunCln compounds (m:n < 3:1) is shown. Photoexcitation of the (NBD) LmCunCln (m:n < 3:1) complexes can produce Q but with quantum efficiencies < 1.0. Photophysical properties of the arylphosphines and their copper(I) halide complexes are reported. The lowest electronic transition of the phosphines associated with an obscured absorption band at ~300nm is classified as an ℓ → aπ transition. Coordination to copper(I) halides brings about an enhancement of the ℓ → aπ transition of the ligand. The term σ,d → aπ is used to describe the lowest electronic transition of the complexes indicating that both the σ bond of the phosphorus lone electron pair to the metal and the d-d orbital bonding of the metal to the phosphorus are involved in an electron excitation from the phosphorus to an antibonding phenyl-π-system (aπ). The photophysical properties of Zn(II), Cu(I), and Ni(0) complexes of MePh2P are shown to follow the concept of a σ,d → aπ electronic transition.

Checksum

1d3709b5f603d84b7d270af672e98dae

Download

Included in

Chemistry Commons

Share

COinS

Copyright for this work is retained by the student. If you have any questions regarding the inclusion of this work in the Digital Commons, please email us at .