This work describes one-step syntheses of various stereogenic-at-boron fluorochromes (BOSPYR) via multicomponent reactions involving readily accessible boronic acids, salicylaldehydes, and 2-formylpyrrole hydrazones. The dyes absorb and emit in the visible region of the electromagnetic radiation, and are characterized by large Stokes shifts (2850–4930 cm⁻¹) with weak fluorescence emissions (Φ_fl: 1.5–9.1%). Notably, the dimmed fluorescence of BOSPYRs recovers upon transition to viscous media (21-fold for 1a). The representative compound 1a exhibits clear Cotton effects with dissymmetry factors of ca. |g_abs| ∼ 1.9 × 10⁻³ in the visible region, indicating efficient asymmetry induction to the chromophore. The X-ray molecular structure of 1a shows that the chromophore deviates from planarity by 17.2°, which may contribute significantly to the inherent chirality of the fluorophore. A computational examination of excited states by time-dependent density functional theory (TD-DFT) identifies the emission mechanism as arising from a locally-excited (LE) state.

中文翻译：

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硼酸、水杨醛和 2-甲酰吡咯腙的立体原硼荧光团 （BOSPYR） 的多组分合成


这项工作描述了通过涉及易得硼酸、水杨醛和 2-甲酰吡咯腙的多组分反应实现各种立体硼荧光染料 （BOSPYR） 的一步合成。染料在电磁辐射的可见区域吸收和发射，其特征是斯托克斯位移大 （2850–4930 ^cm-1） 和弱荧光发射 （Φ_fl： 1.5-9.1%）。值得注意的是，BOSPYR 的暗淡荧光在过渡到粘性介质时恢复（1a 的 21 倍）。代表性化合物 1a 表现出明显的 Cotton 效应，具有 ca 的不对称因子。|G_ABS |∼ 1.9 × 10⁻³，表明对发色团的有效不对称诱导。1a 的 X 射线分子结构显示发色团偏离平面度 17.2°，这可能对荧光团的固有手性有很大影响。通过时间依赖性密度泛函理论 （TD-DFT） 对激发态进行计算检查，确定发射机制由局部激发 （LE） 态产生。