Liske Annika, Wallbaum Lars, Hölzel Torsten, Föller Jelena, Gernert Markus, Hupp Benjamin, Ganter Christian, Marian Christel M, Steffen Andreas
Faculty for Chemistry and Chemical Biology , TU Dortmund University , Otto-Hahn-Strasse 6 , 44227 Dortmund , Germany.
Inorg Chem. 2019 May 6;58(9):5433-5445. doi: 10.1021/acs.inorgchem.9b00337. Epub 2019 Apr 19.
A series of easily accessible linear N-heterocyclic carbene (NHC) copper(I) complexes, bearing pyridine (py) and its derivatives as chromophore ligands, are barely emissive in the single-crystalline solid state. However, their powders, neat films, and dilute doped films of poly(methyl methacrylate) (PMMA; 1-10%) show very intense blue-to-blue-green photoluminescence with remarkable quantum yields φ of up to 87% and microsecond lifetimes, indicative of triplet states being involved. These luminescence properties are similar to trigonal coordinated NHC copper(I) bis(pyridine) complexes, which we have also isolated and characterized with respect to their structures and photophysics. Our spectroscopic and theoretical studies provide detailed insight into the nature of the luminescence enhancing effect of the linear two-coordinated copper(I) compounds, which is based on the formation of Cu-F interactions between the BF anions and [Cu(NHC)(2-R-py)] (R = H, Me, Ph) cations. These interactions are absent in the single crystals but lead to a distorted ground-state structure in the precipitated powders or in PMMA films, giving rise to high k. In addition, we found that our linear copper(I) complexes exhibit mechanochromic luminescence because grinding of the single crystals leads to enhanced emission intensity. In light of the recently reported cation-anion contact-induced mechanochromic luminescence of two-coordinated copper(I) complexes, this study supports the generality of this new mechanism for the design of mechanoresponsive phosphorescent materials.
一系列易于制备的线性N-杂环卡宾（NHC）铜（I）配合物，以吡啶（py）及其衍生物作为发色团配体，在单晶固态下几乎不发光。然而，它们的粉末、纯膜以及聚甲基丙烯酸甲酯（PMMA；1 - 10%）的稀掺杂膜表现出非常强烈的蓝到蓝绿色光致发光，量子产率φ高达87%，寿命为微秒级，表明涉及三重态。这些发光性质与三角配位的NHC铜（I）双（吡啶）配合物相似，我们也对其结构和光物理性质进行了分离和表征。我们的光谱和理论研究详细深入地了解了线性二配位铜（I）化合物发光增强效应的本质，这是基于BF阴离子与[Cu（NHC）（2 - R - py）]（R = H、Me、Ph）阳离子之间形成的Cu - F相互作用。这些相互作用在单晶中不存在，但在沉淀粉末或PMMA膜中导致基态结构扭曲，从而产生高k值。此外，我们发现我们的线性铜（I）配合物表现出机械变色发光，因为单晶研磨会导致发射强度增强。鉴于最近报道的二配位铜（I）配合物阳离子 - 阴离子接触诱导的机械变色发光，本研究支持了这种用于设计机械响应性磷光材料的新机制的普遍性。
