Title

Design, Synthesis, Photophysical, and Electrochemical Studies of Novel Cyclometalated Pyrazolate-Bridged Dinuclear Platinum(II) Complexes

Date of Award

2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Felix Castellano, Ph.D

Second Advisor

Carol Heckman, Ph.D (Committee Member)

Third Advisor

John Cable, Ph.D (Committee Member)

Fourth Advisor

Thomas Kinstle, Ph.D (Committee Member)

Abstract

The present dissertation describes the synthesis, photophysical, and electrochemical properties of a library of pyrazolate-bridged dinuclear cyclometalated platinum(II) complexes. All the complexes investigated here were synthesized with complete characterization. Both the steady state, as well as the time-resolved photophysical techniques employed during the study, helped in defining the photophysical behavior exhibited by such complexes. All the dinuclear Pt(II) complexes discussed here can be expressed by a general formula [Pt(C^N)(µ-R2pz)]2; where C^N is a cyclometalating ligand, and R2Pz are various 3,5-disubstituted pyrazolates. The bridging pyrazolates initiates the metal-metal interaction by building up steric strain within the resulting A-frame topology of the complexes. All the Pt(II) complexes are strongly emissive at room temperature. The influence of the nature of cyclometalating ligand, and the bridging pyrazolates on the photophysical and electrochemical behavior displayed by the complexes were thoroughly investigated. Both room temperature and low temperature measurements aided in distinguishing the nature of lowest energy emissive state present in such complexes. The second part of this dissertation merges our research interest in metal-organic light harvesting chromophores and MLCT complexes with extended lifetime. The dinuclear platinum(II) complexes investigated, have a 4-piperidinyl-1,8-naphthalimide (PNI) unit covalently attached to the cyclometalating 2-phenylpyridine ligand. The resulting bichromophoric complex displayed an enhanced light harvesting ability as compared to the parent dimers. Our study is an effort towards understanding the influence of increased metal-metal interaction on the establishment of a thermal equilibrium between the 3PNI and the 3MMLCT excited states.