4-Ethoxy-2-(pyridin-2-yl)-5-(3,4,5-trimethoxyphenyl)thiazole (EPTT) was prepared in a four-step synthetic protocol. Column shaped single crystals of EPTT were obtained from a saturated EtOH solution. Both single crystals and a THF solution of EPTT were investigated in terms of their photophysical properties and electronic structure. The crystals showed very intense fluorescence upon photoexcitation as well as a red shifted emission maximum compared to a THF solution of EPTT (single crystals: λ_em = 523 nm, Φ_FL = 0.82, THF solution λ_em = 477 nm, Φ_FL = 0.67). Quantum chemical methods were then employed to unravel the underlying fundamental transitions and explain the experimental results. Calculations for a small dye cluster modeled after the x-ray crystal structure predicted three dark intermolecular CT states, S₁-S₃, below the intramolecular CT state (S₄) for EPTT in the crystalline state. Photoexcitation and subsequent relaxation along the excited states relaxation pathways may populate the low-lying dark intermolecular CT states, which in consequence leads to an exciton moving along the stacked dyes in the crystal. This finding explains the significantly enhanced red-shift of the solid-state fluorescence of EPTT compared to the dissolved dye.

以四步合成方案制备4-乙氧基-2-（吡啶-2-基）-5-（3,4,5-三甲氧基苯基）噻唑（EPTT）。从饱和的EtOH溶液中获得EPTT的柱状单晶。研究了EPTT的单晶和THF溶液的光物理性质和电子结构。将晶体在光激发显示出非常强烈的荧光，以及作为红色相比的THF溶液移位发射最大值EPTT单晶（：λ _EM  = 523纳米，Φ _FL  = 0.82，THF溶液λ _EM  = 477纳米，Φ _FL = 0.67）。然后采用量子化学方法来揭示潜在的基本转变并解释实验结果。根据X射线晶体结构建模的小染料簇的计算预测了处于结晶态的EPTT的分子内CT态（S ₄）以下的三个暗分子间CT状态S ₁ -S ₃。沿激发态的光激发和随后的弛豫途径可能会填充低洼的暗分子间CT态，从而导致激子沿着晶体中堆积的染料移动。该发现解释了与溶解的染料相比，EPTT的固态荧光显着增强的红移。