Synthesis, tuning, photochemical, and photophysical studies of platinum(II) polyimine complexes

Daniel Paul Lazzaro, Purdue University

Abstract

Transition metal photochemistry, specifically of those complexes with open coordination sites have long been studied for applications such as sensors in solution and the solid state as they are sensitive to their environment. Those that exhibit solution photoluminescence have the ability to show quenching in coordinating solvents. This phenomenon has been extensively explored in pseudo-square planar platinum(II) complexes with terpyridine ligands. Chapter one is a general description of photochemical processes, as well as, an introduction to platinum(II) photochemistry, photophysics, and exciplex quenching. Chapter two expands on these concepts and presents a complex with an extended phenazine moiety built into the ligand system. It exhibits regiospecific quenching by Lewis bases at the open coordination site of platinum, but also Lewis acids at the distal heteroatoms of the ligand. The synthesis, photochemistry, and detailed quenching mechanisms are explained. The dual sensing ability of this complex represents a first in the field. Chapter three presents a series of novel platinum(II) complexes with substituted terpyridine ligands that incorporate for the most part electron donating groups. Also, the co-ligand of the complexes is a carbometalated phenyl ring. The chapter describes why complexes of the parent type [Pt(trpy)Ph]+ are non-emissive in solution owing to 3SBLCT excitation and how introducing 3ILCT or 3IL character leads to solution emission at room temperature. Due to the change in excited state character, the complexes presented in this chapter are the first of their kind to show room temperature solution emission of platinum(II) terpyridine complexes with phenyl co-ligands, including one with an extremely long, 45 μs excited state lifetime. The synthesis, photochemistry, and interpretation of the excited state character of five complexes are explained in detail. Chapter four extends the work of chapters two and three as it describes a series of complexes that incorporate cyclometalating phenanthroline based ligands modified with electron donating groups in an effort to tune the excited state emission energies. The overall goal of this was to design a molecule much like that discussed in chapter two that is even more sensitive to Lewis acids in solution. The original design led to some complexes being very photosensitive, making photophysical studies difficult. A mechanism for the degradation was tested and new complexes designed to circumvent the problem. The design, synthesis, photochemistry, and photophysics of these complexes are described herein.

Degree

Ph.D.

Advisors

McMillin, Purdue University.

Subject Area

Inorganic chemistry|Physical chemistry

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