Towards Nature-Inspired Antenna Systems for Artificial Light-harvesting Devices

With the growing demand for cleaner energy, decoding the design principles of natural antenna complexes has become essential for designing efficient artificial devices. Thus, supramolecular engineering of dye materials relies on both the photophysics of individual components and the assembly-induced coupling patterns. This thesis advances the computational design and mechanistic understanding of molecular systems for light-harvesting, energy transfer, and photoresponsive applications, mainly through multiconfigurational quantum chemistry and excitonic modeling. The present work bridges molecular-level insights to functional material design by focusing on three distinct chromophore classes: (bacterio)chlorophyll (BChl)-like systems, azobenzene-derived models, and cyanine-based dyes. First, we focused on natural and synthetic (B)Chl systems. Regarding the monomers, we explored a series of chemically and structurally modified (B)Chl pigments through computational chemistry to evaluate their electronic and spectroscopical properties. Subsequently, we systematically surveyed how geometric arrangements of BChl dimers modulate excitonic couplings and spectral characteristics using a Frenkel exciton Hamiltonian (FEH) model coupled with multiconfigurational monomeric wave functions. The extensive high-throughput analysis of over 11,000 BChl dimeric configurations demonstrated how intermolecular distances, translation, and rotations around different axes drive transitions between H-, J-, X-, and (+)-aggregate types, along with their corresponding distinct spectral and energetic landscapes. The same FEH approach was applied to the Photo System II reaction center, where multireference calculations quantified electronic couplings between Chls, highlighting the significance of accurate monomeric and excitonic calculations in understanding energy transfer events. Spectroscopic tuning principles were then extended to the azobenzene dye, for which we constructed a library of chemically derived models. We found that substituents’ chemical nature and position significantly tune the monomeric models’ chemistry in the studied cases. Then, the evaluation was expanded to the excitonic properties of homo- and, more interestingly, heterodimeric aggregates composed of π-stacked and slip-stacked arrangements. Our results showed how heterodimeric dyes, constructed with monomers of particular chemical and physical characteristics, can exhibit strong excitonic coupling with considerable spectral shifts and excitonic properties that are different from those achieved with homodimers. Finally, we present our preliminary findings based on the multiconfigurational multireference calculations on Cyanine-based fluorophores. The main focus was on the influence of optimizing the geometry and/or including the implicit solvent effect on the electronic structure, the energetics of the dyes, and on the resulting excitonic behavior for a series of homodimeric models. By integrating quantum chemistry with organic material science, this project establishes computational strategies inspired by nature for color-tuning and tailoring chromophores. The detailed findings provide design principles for artificial light-harvesting systems and advanced exciton-based materials.