Exploring Electronic and Conformational Attributes of an Organic Donor-Bridge-Acceptor Molecular System

Abstract

This research explores the electronic properties and conformational dynamics of the ZnP-COPV-${\mathrm{C}}_{60}$ (Zinc Porphyrin - Carbon bridged Oligo Phenylenevinylene - Fullerene) organic semiconductor via specialized Density Functional Theory (DFT) and Molecular Dynamics (MD) computational techniques. First, through DFT calculations, essential HOMO (Highest Occupied Molecular Orbital), LUMO (Lowest Unoccupied Molecular Orbital), and Molecular Electrostatic Potential (MEP) electronic attributes are meticulously dissected providing insights into the intricate charge transfer processes between the constituent donor-acceptor moieties. Furthermore, MD simulations are employed to unveil the molecular system's multifaceted conformational flexibility and stability. The Root-mean-squared deviation (RMSD), end-to-end distance, and torsional angles quantitative analysis of conformational attributes support the carbon-bridged oligo-phenylenevinylene (COPV) molecular wire's $\pi$-skeleton planar and rigid conformation. This minimal end-to-end distance variation (within $\pm 1$ Å) compared to the initially extended structure and the constrained torsional motion (within $\pm {20}^{\circ }$ for ZnP-COPV and $\pm {30}^{\circ }$ for COPV-${\mathrm{C}}_{60}$) after thermalization showcases COPV's ability to maintain structural rigidity over time, aligning with the concept of effective $\pi$-conjugation. Finally, through the lens of time dependent (TD)-DFT, the dynamic evolution of the HOMO–LUMO energy gap, TD-DFT excitation energies and oscillator strengths are explored as the molecular structure transforms over time. The observed energy gap variation underscores the molecule's adaptability in the face of structural modifications, hinting at an intriguing connection between structural stability and enhanced electronic properties. The research provides a comprehensive understanding of the intricate interplay between conformational dynamics and electronic attributes in organic semiconductors, providing quantitative insights crucial for designing stable, high-performance materials for cutting-edge optoelectronic applications and helping advance the collective understanding of sustainable energy conversion.