Tuning Spectral Properties of Anthracenes through Substitution

Abstract

Heteroatom substitution offers a powerful means of tuning the spectral properties of acenes, yet a general structure–property relationship valid across different heteroacene families has been lacking. In this study, we extend a previously applied analysis based on the algebraic diagrammatic construction scheme for electronic excitations (ADC) framework to a broader family of heteroacenes, including aza-, phospha-, and halogen-substituted anthracenes. Decomposition of the ADC diagonal elements and the corresponding perturbative effects from ADC(2) → ADC(1) → ADC(0) reveals orbital energy differences as the primary driver of excited state mixing and thus of the resulting oscillator strengths. This uncovers how substituent type and position shapes spectral intensities of the low-lying ππ* electronic transitions, namely, ¹L_s (¹L_b) and ¹B_b. Tip substitution consistently enhances the orbital energy difference and leads to bright α-bands (¹L_s/¹L_b), whereas side substitution produces more symmetric mixing of configurations and weak α-bands. Across halogen series, increasing electronegativity while keeping the position unchanged generally leads to higher oscillator strength of the ¹L_s (¹L_b) state. These results provide a unified, general rule for tuning the spectral properties by substitution and/or heteroatom replacement.