Date of Award

5-2024

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Chemistry and Chemical Engineering

First Advisor

Roberto Peverati

Second Advisor

Manasvi Lingam

Third Advisor

Boris Akhremitchev

Fourth Advisor

Jessica Smeltz

Abstract

In the search for extraterrestrial life, biosignatures play a crucial role in identifying its putative traces. A commonly known and robust biosignature is the Vegetation Red Edge (VRE), which can be described as a sharp increase of reflectance observed from a planet and stems from the light absorption of photopigments in specific regions in the electromagnetic spectrum. For Earth, this VRE is known to occur around 700 nm, however, if the photopigments absorb light in different regions and have different structures the VRE could experience a wavelenght shift.

In this work, Chlorophyll a and a potential photopigment precursor called Phot0 were computationally modeled using a variety of DFT functionals. The results indicate that these photopigments are best described using the PW6B95 global hybrid functional or the B2PLYP double hybrid functional since both of these methods provide relatively accurate results at low computational cost. Additionally, the influence of the metal center on the peak shift in the absorption spectrum of phot0 was explored. Elements with a higher electronegativity than magnesium, which is the metal center found in chlorophylls, shift the peak towards a lower wavelength, while a relatively lower electronegativity of the metal center results in a redshifted peak.

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