Lash Timothy D, Colby Denise A, Graham Shelley R, Ferrence Gregory M, Szczepura Lisa F
Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, USA.
Inorg Chem. 2003 Nov 3;42(22):7326-38. doi: 10.1021/ic030166b.
Four azuliporphyrins, two meso-unsubstituted and two meso-tetraaryl substituted, were investigated in the synthesis of novel organometallic compounds. The meso-unsubstituted or "etio" series azuliporphyrins 8 reacted with nickel(II) acetate, palladium(II) acetate, and platinum(II) chloride in DMF to give the corresponding chelates 14-16, where the metal cation lies within the macrocyclic cavity and binds to all three nitrogens and the internal carbon atom. The newly available meso-tetraarylazuliporphyrins 13 similarly afforded the corresponding nickel(II), palladium(II), and platinum(II) complexes, 17-19, respectively. The new organometallic complexes are stable nonpolar compounds and were fully characterized spectroscopically and by mass spectrometry. The UV-vis data indicate that these complexes, in common with the parent azuliporphyrin system 8, do not possess porphyrin-type aromaticity. However, electron donation from the azulene unit can give rise to dipolar resonance contributors that provide a degree of carbaporphyrin-type aromatic character. The platinum(II) azuliporphyrins 16 gave noteworthy proton NMR spectra where the meso-protons showed satellite peaks due to transannular coupling to platinum-195. The pyrrolic protons of the platinum(II) meso-tetraarylazuliporphyrin 19b also showed similar satellite peaks due to coupling from the platinum-195 isotope. The electrochemistry of free base tetraphenylazuliporphyrin 13a and the related nickel(II) and palladium(II) complexes was investigated using cyclic voltammetry, and these data indicate that metal coordination improves the reversibility of the ligand-based oxidations. Nickel(II) azuliporphyrin 14a and palladium(II) tetrakis(4-chlorophenyl)azuliporphyrin 18b were also structurally characterized by X-ray crystallography. The macrocyclic core of the palladium(II) complex 18b was significantly more planar than the nickel(II) derivative 14b, and this difference was attributed to the better size match between the azuliporphyrin cavity and the larger palladium(II) ion. The straightforward synthesis of metalloazuliporphyrins under mild conditions, and their interesting spectroscopic, electrochemical, and structural features, demonstrates that the azuliporphyrin system holds great promise as a platform for organometallic chemistry.
在新型有机金属化合物的合成中，对四种氮杂卟啉进行了研究，其中两种是中位未取代的，两种是中位四芳基取代的。中位未取代或“初卟啉”系列氮杂卟啉8与醋酸镍(II)、醋酸钯(II)和氯化铂(II)在N,N-二甲基甲酰胺中反应，得到相应的螯合物14 - 16，其中金属阳离子位于大环腔内，并与所有三个氮原子和内部碳原子结合。新得到的中位四芳基氮杂卟啉13同样分别得到了相应的镍(II)、钯(II)和铂(II)配合物17 - 19。这些新型有机金属配合物是稳定的非极性化合物，并通过光谱和质谱进行了全面表征。紫外可见光谱数据表明，这些配合物与母体氮杂卟啉体系8一样，不具有卟啉型芳香性。然而，薁单元的电子给予可以产生偶极共振贡献体，从而提供一定程度的碳卟啉型芳香特征。铂(II)氮杂卟啉16给出了值得注意的质子核磁共振谱，其中中位质子由于与铂-195的跨环耦合而显示出卫星峰。铂(II)中位四芳基氮杂卟啉19b的吡咯质子也由于铂-195同位素的耦合而显示出类似的卫星峰。使用循环伏安法研究了游离碱四苯基氮杂卟啉13a以及相关的镍(II)和钯(II)配合物的电化学性质，这些数据表明金属配位提高了基于配体的氧化反应的可逆性。镍(II)氮杂卟啉14a和钯(II)四(4-氯苯基)氮杂卟啉18b也通过X射线晶体学进行了结构表征。钯(II)配合物18b的大环核心比镍(II)衍生物14b明显更平面，这种差异归因于氮杂卟啉腔与较大的钯(II)离子之间更好的尺寸匹配。在温和条件下直接合成金属氮杂卟啉及其有趣的光谱、电化学和结构特征表明，氮杂卟啉体系作为有机金属化学的一个平台具有很大的潜力。
