Non-Condon Effects in Nonadiabatic Dynamics and Intersystem Crossing Jennifer R DeRosa

Format:

Book

Thesis/Dissertation

Author/Creator:

DeRosa, Jennifer R., author.

Contributor:

University of Pennsylvania. Chemistry., degree granting institution.

Language:

English

Subjects (All):

0219.

0485.

0494.

0599.

Local Subjects:

0219.

0485.

0494.

0599.

Physical Description:

1 electronic resource (112 pages)

Contained In:

Dissertations Abstracts International 87-07B

Place of Publication:

Ann Arbor : ProQuest Dissertations and Theses, 2025

Language Note:

English

Summary:

Many chemical processes such as photoexcited triplet energy transfer, radical electron and hole transfer, and intersystem crossing are dictated by nonadiabatic dynamics. The theory of nonadiabatic dynamics itself has been a long studied phenomenon, most prominently since Closs and coworkers measured the existence of the inverted regime as predicted by Marcus in the 20th century. The work in this thesis revisits the famous Marcus nonadiabatic rate equation and quantifies its shortcomings in a few crucial cases. The first two chapters revisit the findings of Closs et. al. who observed a clear connection between electron transfer and triplet energy transfer rates. The work presented focuses on a specific case where the predicted rate relation fails, namely the C13-ae ([3,equatorial]-naphthalene-cyclohexane-[1,axial]-benzophenone). To better understand this disagreement, in Chapter 1 we introduce and employ a novel scheme to sample the seam between two diabatic electronic states (E-SHAKE) through which we reveal the breakdown of the Condon approximation (id est the notion that the diabatic coupling is invariant to geometry) and the presence of a conical intersection. Furthermore, in Chapter 2 we investigate the applicability of the Condon approximation in the context of both electron transfer (ET) and triplet energy transfer (TET) from a wavefunction analysis of a one-dimensional model. Our findings show that the Condon approximation appears less applicable for TET than for ET and we extend our analysis to the C-13-ae molecule from Chapter 1. Finally, in Chapter 3 we revisit the naked transition metal cation (Ti+) and methanol reaction and go beyond the standard Landau-Zener (LZ) picture when modeling the intersystem crossing (ISC) rate between the lowest doublet and quartet states. We use both (i) unconstrained Born-Oppenheimer molecular dynamics (BOMD) calculations with an approximate two-state method to estimate population transfer between spin diabetes and (ii) constrained dynamics to explore energetically accessible portions of the NDOF − 1 crossing seam, where NDOF is the total number of internal degrees of freedom. Whereas previous LZ calculations (that necessarily relied on the Condon approximation to be valid) fell short and predicted much slower crossing probabilities than shown in experiment, we show that ISC can occur rapidly because the spin-orbit coupling (SOC) between the doublet and quartet surfaces can vary by two orders of magnitude (depending on where in the seam the crossing occurs during dynamics) and the crossing region is revisited multiple times during a dynamics run of a few hundred femtoseconds. We further isolate the two important nuclear coordinates that tune the SOC and modulate the transition, highlighting exactly how and why organometallic ISC can occur rapidly for small systems with floppy internal nuclear vibrational modes. Altogether, our approach makes clear that, while Marcus theory is a good starting point for understanding nonadiabatic behavior, when it comes to realistic systems with many nuclear degrees of freedom and nontrivial electron-electron correlation, there remains a great deal of chemistry to be learned by developing new approaches to analyze potential energy surfaces and nonadiabatic crossings in high dimensional spaces

Notes:

Advisors: Subotnik, Joseph E. Committee members: Rappe, Andrew M.; Nitzan, Abraham; Lester, Marsha I.

Source: Dissertations Abstracts International, Volume: 87-07, Section: B.

Ph.D. University of Pennsylvania 2025

Vendor supplied data

Local Notes:

School code: 0175

ISBN:

9798276005799

Access Restriction:

Restricted for use by site license