Modulating anthracene excimer through guest engineering in two-dimensional lead bromide hybrids

Abstract

A full understanding of the excimer formation and structure–property relationship is essential to their development in organic electronics. Herein, we propose a template strategy for finely modulating the stacking configuration of 9-dimethylaminomethyl-10-chloroanthracene (DCAn) dimers in two-dimensional (2D) (DCAn)₄Pb₃Br₁₀·2CH₃(CH₂)_X−1OH (1-CX, 1 ≤ X ≤ 8). By introducing alcohol guests with varied carbon lengths from methanol to octanol, 1-CX with different stacking motifs of (anthracene) An dimers are obtained. The fine control on stacking parameters, including interplanar distance, overlap ratio, offset along long (d_x) and short (d_y) axis and intersection angle of An allows a deep insight into the key factors of excimer formation. The experimental and computational results confirm that the excimer interaction is strongly determined by the excimer types (anthracene or naphthalene) and interplanar overlap. An anthracene-type excimer is formed for 1-CX (6 ≤ X ≤ 8) once d_x locates in the range of 1.08–1.23 Å, while 1-CX (1 ≤ X ≤ 5) adopts the naphthalene-type excimer for 1.55 ≤ d_x ≤ 1.75 Å. Due to the stronger anthracene-type excimer interaction, a great bathochromic shift of photoluminescence is observed for 1-CX (6 ≤ X ≤ 8). Additionally, rod-like 1-CX exhibits a high aspect ratio of ∼72, thereby generating an excellent performance on optical waveguide with an optical loss coefficient of ∼3 dB mm⁻¹. This work not only reveals the key factors on An excimer formation, but also provides an effective strategy for better understanding the structure–property of molecular excimers.