Photochemical Sciences Ph.D. Dissertations

Excited State Dynamics and Chemical Bond Rearrangement in Ruthenium Nitrosyl Complexes and Several Other Heavy-Atom-Containing Compounds

Date of Award

2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Alexander N. Tarnovsky (Committee Chair)

Second Advisor

Amelia Carr (Other)

Third Advisor

John R. Cable (Committee Member)

Fourth Advisor

Alexis D. Ostrowski (Committee Member)

Abstract

Ultrafast time-resolved pump-probe spectroscopy is an ultimate method for revealing fundamental photophysical and photochemical processes that govern the evolution of molecular systems. This method can be used to study organic, inorganic, biological molecules, as well as materials, unraveling the response of the sample to photoexcitation on very rapid timescales from femtoseconds (10-15 s) to picoseconds (10-12 s), which response frequently defines molecular properties and functions. Excited-state relaxation dynamics of a paradigm ruthenium nitrosyl complex, an important sub-class of nitric oxide carriers, is studied by means of ultrafast dispersed, broadband transient absorption spectroscopy. A computational extension is performed for related NO-releasers such as trans [RuNOL2Cl3] complexes which possess coordinated derivatives of biologically-relevant nicotinic and isonicotinic acids. Further studies to develop NO releasers, including those involving covalent linkage sites as isonicotinic/nicotinic derivatives for potential application as photochemical drugs, can rely on the findings in the ultrafast study of [RuNOCl5]2- dynamics as involvement of the triplet states rather than linkage isomers. Further, molecular properties of compounds related to the perovskite-based photovoltaic were computationally investigated. The electron-rich series of [I3]-, [TeI4]2-, and [BiI6]3- compounds were discussed in detail with a focus on three-center four-electron bond, which plays an important role in the compounds containing heavy-atoms. Excited-state relaxation dynamics in a polyhalogenated compound (CH2BrI) were investigated by means of computational dynamics on the earliest timescale of 100 fs following excitation of this molecule into two electronic states of spectroscopic interest. The computed pump probe spectra yield the time occurrence and spectral position of the absorption and stimulated emission transitions of the involved product states. The results are instrumental for the future ultrafast pump-probe experiments on CH2BrI and related polyhalogenated alkanes.

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