Presentation Title

Structure-Function Relations: Modeling Mega-Stokes Shifts

Project Collaborators

Matthew Liptak (Primary Investigator), Morgan Cousins (Graduate Student Mentor)

Abstract

Stokes shift is a critical metric of photophysical properties. A molecule’s Stokes shift is the energy difference between the lowest wavelength of light it absorbs and the lowest wavelength of light it emits. Small Stokes shifts allow for self-quenching, a phenomenon by which compounds immediately reabsorb the light they emit. Self-quenching is of great significance to industrial and commercial applications for it effectively negates a molecule’s ability to produce usable light. Conversely, large Stokes shifts are highly desirable for they indicate an inhibition of self-quenching. The Stokes shifts of [1,2,3]triazolo[1,5-a]pyridinium (TOP) and [1,2,3]triazolo[1,5-a]quinolinium (TOQ) dyes are so extraordinarily large that they have been dubbed Mega-Stokes shifts. To investigate this phenomenon, computational chemistry, particularly time-dependent density functional theory (TDDFT), was used to model the photophysics of TOP and TOQ dyes. Low-level computations proved poor predictors of empirically known constants, but more complex long-range calculations have yielded very accurate models. This has allowed for study of the relationship between the dyes’ conformational and electronic structures which is hypothesized to be key to the generation of a Mega-Stokes shift. Understanding the mechanisms underlying the TOP and TOQ dyes’ exceptional photophysical characteristics provides a lead into synthesizing new materials with Mega-Stokes shifts.

Primary Faculty Mentor Name

Matthew Liptak

Graduate Student Mentors

Morgan Cousins

Status

Undergraduate

Student College

College of Arts and Sciences

Program/Major

Chemistry

Primary Research Category

Engineering & Physical Sciences

Second Program/Major

Mathematics

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Structure-Function Relations: Modeling Mega-Stokes Shifts

Stokes shift is a critical metric of photophysical properties. A molecule’s Stokes shift is the energy difference between the lowest wavelength of light it absorbs and the lowest wavelength of light it emits. Small Stokes shifts allow for self-quenching, a phenomenon by which compounds immediately reabsorb the light they emit. Self-quenching is of great significance to industrial and commercial applications for it effectively negates a molecule’s ability to produce usable light. Conversely, large Stokes shifts are highly desirable for they indicate an inhibition of self-quenching. The Stokes shifts of [1,2,3]triazolo[1,5-a]pyridinium (TOP) and [1,2,3]triazolo[1,5-a]quinolinium (TOQ) dyes are so extraordinarily large that they have been dubbed Mega-Stokes shifts. To investigate this phenomenon, computational chemistry, particularly time-dependent density functional theory (TDDFT), was used to model the photophysics of TOP and TOQ dyes. Low-level computations proved poor predictors of empirically known constants, but more complex long-range calculations have yielded very accurate models. This has allowed for study of the relationship between the dyes’ conformational and electronic structures which is hypothesized to be key to the generation of a Mega-Stokes shift. Understanding the mechanisms underlying the TOP and TOQ dyes’ exceptional photophysical characteristics provides a lead into synthesizing new materials with Mega-Stokes shifts.