Yang Qin, Fusè Marco, Bloino Julien
Scuola Normale Superiore, Pisa, Italy.
Front Chem. 2020 Sep 15;8:801. doi: 10.3389/fchem.2020.00801. eCollection 2020.
Over the last decade, molecules capable of emitting circularly polarized light have attracted growing attention for potential technological and biological applications. The efficiency of such devices depend on multiple parameters, in particular the magnitude and wavelength of the peak of emitted light, and also on the dissymmetry factor for chiral applications. In light of these considerations, molecular systems with tunable optical properties, preferably in the visible spectral region, are particularly appealing. This is the case of boron dipyrromethene (BODIPY) dyes, which exhibit large molecular absorption coefficients, have high fluorescence yields, are very stable, both thermally and photochemically, and can be easily functionalized. The latter property has been extensively exploited in the literature to produce chromophores with a wide range of optical properties. Nevertheless, only a few chiral BODIPYs have been synthetized and investigated so far. Using a recently reported axially chiral BODIPY derivative where an axially chiral BINOL unit has been attached to the chromophore unit, we present a comprehensive computational protocol to predict and interpret the one-photon absorption and emission spectra, together with their chiroptical counterparts. From the physico-chemical properties of this molecule, it will be possible to understand the origin of the circularly polarized luminescence better, thus helping to fine-tune the properties of interest. The sensitivity of such processes require accurate results, which can be achieved through a proper account of the vibrational structure in optical spectra. Methodologies to compute vibrationally-resolved electronic spectra can now be applied on relatively large chromophores, such as BODIPYs, but require more extensive computational protocols. For this reason, particular attention is paid in the description of the different steps of the protocol, and the potential pitfalls. Finally, we show how, by means of appropriate tools and approaches, data from intermediate steps of the simulation of the final spectra can be used to obtain further insights into the properties of the molecular system under investigation and the origin of the visible bands.
在过去十年中，能够发射圆偏振光的分子因其潜在的技术和生物应用而受到越来越多的关注。此类器件的效率取决于多个参数，特别是发射光峰值的大小和波长，以及用于手性应用的不对称因子。鉴于这些因素，具有可调光学性质的分子体系，最好是在可见光谱区域，尤其具有吸引力。硼二吡咯亚甲基（BODIPY）染料就是这种情况，它具有大的分子吸收系数、高荧光产率，在热和光化学方面都非常稳定，并且易于功能化。后一种特性在文献中已被广泛利用，以制备具有广泛光学性质的发色团。然而，到目前为止，仅合成并研究了少数手性BODIPY。使用最近报道的一种轴向手性BODIPY衍生物，其中一个轴向手性联萘酚单元连接到发色团单元，我们提出了一个全面的计算方案来预测和解释单光子吸收和发射光谱及其手性光学对应物。从该分子的物理化学性质出发，将有可能更好地理解圆偏振发光的起源，从而有助于微调感兴趣的性质。此类过程的敏感性需要准确的结果，这可以通过适当考虑光谱中的振动结构来实现。计算振动分辨电子光谱的方法现在可以应用于相对较大的发色团，如BODIPY，但需要更广泛的计算方案。因此，在方案的不同步骤描述以及潜在陷阱方面给予了特别关注。最后，我们展示了如何通过适当的工具和方法，利用最终光谱模拟中间步骤的数据，进一步深入了解所研究分子体系的性质以及可见带的起源。
