Organic singlet diradicaloids promise application in non-linear optics, electronic devices and singlet fission. The stabilization of carbon allotropes/cumulenes (C₁, C₂, C₄) by carbenes has been equally an area of high activity. Combining these fields, we showed recently that carbene scaffolds allow as well for the design of diradicaloids. Herein, we report a comprehensive computational investigation (CASSCF/NEVPT2; fractional occupation DFT) on the electronic properties of carbene–bridge–carbene type diradicaloids. We delineate how to adjust the properties of these ensembles through the choice of carbene and bridge and show that already a short C₂ bridge results in remarkable diradicaloid character. The choice of the carbene separately tunes the energies of the S₁ and T₁ excited states, whereas the bridge adjusts the overall energy level of the excited states. Accordingly, we develop guidelines on how to tailor the electronic properties of these molecules. Of particular note, fractional occupation DFT is an excellent tool to predict singlet–triplet gaps.

中文翻译：

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卡宾衍生的双基类胡萝卜素–单峰裂变的构建基？†

有机单重双基类化合物有望应用于非线性光学，电子设备和单重态裂变。卡宾对碳同素异形体/异丙苯（C ₁，C ₂，C ₄）的稳定作用一直是一个高活性区域。结合这些领域，我们最近表明，卡宾支架也可以用于双自由基的设计。在这里，我们报告了关于卡宾-桥-卡宾型双自由基的电子性质的综合计算研究（CASSCF / NEVPT2;分数职业DFT）。我们描述了如何通过卡宾和桥的选择来调整这些合奏的特性，并表明已经很短的C _2了。桥导致显着的双基性特征。卡宾的选择分别调节S ₁和T ₁激发态的能量，而电桥调节激发态的总能级。因此，我们制定了有关如何调整这些分子的电子性质的指导原则。特别值得注意的是，分数职业DFT是预测单重态-三胞胎间隙的出色工具。