Abstract：
Rhenium(I) complexes of type [Re(CO)3(NN)Cl] (NN = α-diimine) with MLCT absorption in the orange-red region of the visible spectrum have been synthesized and fully characterized, including single crystal X-ray diffraction on two complexes. The strong bathochromic shift of MLCT absorption was achieved through extension of the π-system of the electron-poor bidiazine ligand 4,4\'-bipyrimidine by the addition of fused phenyl rings, resulting in 4,4\'-biquinazoline. Furthermore, upon anionic cyclization of the twisted bidiazine, a new 4N-doped perylene ligand, namely, 1,3,10,12-tetraazaperylene, was obtained. Electrochemical characterization revealed a significant stabilization of the LUMO in this series, with the first reduction of the azaperylene found at E1/2(0/-) = -1.131 V vs. Fc+/Fc, which is the most anodic half-wave potential observed for N-doped perylene derivatives so far. The low LUMO energies were directly correlated to the photophysical properties of the respective complexes, resulting in a strongly red-shifted MLCT absorption band in chloroform with a λmax = 586 nm and high extinction coefficients (ε586nm > 5000 M-1 cm-1) ranging above 700 nm in the case of the tetraazaperylene complex. Such low-energy MLCT absorption is highly unusual for Re(I) α-diimine complexes, for which these bands are typically found in the near UV. The reported 1,3,10,12-tetraazaperylene complex displayed the [Re(CO)3(α-diimine)Cl] complex with the strongest MLCT red shift ever reported. UV-Vis NIR spectroelectrochemical investigations gave further insights into the nature and stability of the reduced states. The electron-poor ligands explored herein open up a new path for designing metal complexes with strongly red-shifted absorption, thus enabling photocatalysis and photomedical applications with low-energy, tissue-penetrating red light in future.
摘要：
合成了[Re（CO）3（NN）Cl]（NN=α-二亚胺）型铼（I）配合物，在可见光谱的橙红色区域具有MLCT吸收，包括对两种配合物的单晶X射线衍射。MLCT吸收的强红移是通过添加稠合苯环通过扩展弱电子联二嗪配体4,4'-联嘧啶的π系统来实现的，产生4,4'-双喹唑啉。此外，在扭曲的联二嗪的阴离子环化后，一种新的4N掺杂的perylene配体，即,1,3,10,12-四氮杂亚烷基,已获得。电化学表征揭示了该系列中LUMO的显着稳定，在E1/2（0/-）=-1.131V时发现的偶氮亚烷基的第一次还原Fc+/Fc,这是迄今为止观察到的N掺杂perylene衍生物的阳极半波势。低LUMO能量与相应复合物的光物理性质直接相关，在四氮杂亚烷基络合物的情况下，在氯仿中产生强烈的红移MLCT吸收带，λmax=586nm，消光系数高（ε586nm>5000M-1cm-1），范围超过700nm。这种低能量MLCT吸收对于Re（I）α-二亚胺配合物非常不寻常，这些波段通常在近紫外线中发现。报道的1,3,10,12-四氮杂亚烷基络合物显示出[Re（CO）3（α-二亚胺）Cl]络合物，具有有史以来最强的MLCT红移。UV-VisNIR光谱电化学研究进一步揭示了还原态的性质和稳定性。本文探索的贫电子配体为设计具有强烈红移吸收的金属络合物开辟了新的途径，从而实现低能量的光催化和光电医学应用，未来会有穿透组织的红光。
