ABSTRACT The focus of the current work investigation was structural isomerism, caused by variations in atomic connectivity and positional isomerism, resulting in unique molecular geometries and electronic structures that significantly influence the photoelectronic behavior of isomers. This study examines three sets of structural isomers, based on tetracene, pyrene, and chrysene cores, namely PTA‐1 and PTA‐2 , PTA‐3 and PTA‐4 , PTA‐5 and PTA‐6 , respectively. Among all the isomers, PTA‐5 has the best aromatic character, with average HOMA score of 0.749, underscoring that the substitution position holds the key to π‐electron delocalization. The charge transfer character of excited states is examined through Hole–Electron analysis. Among all the investigated systems, PTA‐5 exhibits the highest D ‐index with a value of 0.529 Å, clearly indicating pronounced charge transfer in excited states. A quantum chemical approach utilizing the M06‐2X functional and 6–311G** basis set is employed to examine the optical and nonlinear optical properties. PTA‐1 stands out with a higher α iso value (110.75 × 10 −36 esu), whereas PTA‐3 exhibits the largest with the value of 486.23 × 10 −36 esu, with the lowest transition energy 3.54 eV. Additionally, a red‐shift absorption peak at 312.7 nm in the UV‐visible spectra of PTA‐5 indicates potential of these compounds in optoelectronic applications.
Saddique et al. (2026) studied this question.