We report a detailed investigation of a series of new charge-transfer (CT) complexes assembled via a two-point complementary hydrogen bonding (H-bonding) of diindolopyrrole (DIP) electron donors with o-quinone and diazafluorenone acceptors. Unidirectional polarization through the DD⋯AA type H-bonding leads to a dramatic perturbation of electronic levels of the donor and the acceptor. π-Stacking of the H-bonded pairs results in strong charge-transfer (HOMO–LUMO) interactions in their ground state, manifested in low energy optical absorption. Density functional theory (DFT) calculations predict a H-bonding induced rise of the HOMO^D (by up to 0.5 eV) and lowering of the LUMO^A (by up to 0.7 eV). As a result, the complexes of relatively weak electron donors and acceptor ability exhibit remarkably low optical energy gaps (down to <0.8 eV), that can be tuned by varying the ionization potential and electron affinity of the individual components. Single crystal X-ray analysis for 6 complexes displayed H-bond lengths between 1.9 and 2.3 Å and short π-stacking distances (≥3.2 Å), in line with strong donor–acceptor interactions. Thin-film transistors of such a H-bonded complex, fabricated by vacuum co-sublimation of PhDIP and pyrenetetraone, showed ambipolar charge transport with unusual ‘double dip’ characteristics.

中文翻译：

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通过互补的两点氢键进行供体-受体共晶体的带隙工程

我们报告了一系列新的电荷转移（CT）复合物的详细研究，该复合物是通过二吲哚并吡咯（DIP）电子给体与邻醌和二氮杂芴酮受体的两点互补氢键（H键）组装而成的。通过DD⋯AA型H键的单向极化导致给体和受体电子能级的剧烈扰动。H键对的π堆积会在其基态下导致强烈的电荷转移（HOMO-LUMO）相互作用，表现为低能量的光吸收。密度泛函理论（DFT）计算可预测H键引起的HOMO ^D的升高（高达0.5 eV）和LUMO ^A的降低（高达0.7 eV）。结果，相对弱的电子给体和受体能力的配合物表现出非常低的光能隙（低至<0.8 eV），可以通过改变各个组分的电离势和电子亲和力来调节。对6个配合物的单晶X射线分析显示H键长度在1.9和2.3Å之间，并且π堆积距离短（≥3.2Å），这与强的供体-受体相互作用相符。通过PhDIP和pyr四酮的真空共升华制造的这种H键复合物的薄膜晶体管显示出双极性电荷传输，具有异常的“双浸”特性。