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• 作者：Xiaohui Cai ; Maria Pia Donzello ; Elisa Viola ; Corrado Rizzoli ; Claudio Ercolani ; Karl M. Kadish
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：August 3, 2009
• 年：2009
• 卷：48
• 期：15
• 页码：7086-7098
• 全文大小：979K
• 年卷期：v.48,no.15(August 3, 2009)
• ISSN：1520-510X

文摘

2,3-Dicyano-5,6-di-2-pyridylpyrazine, [(CN)₂Py₂Pyz], which autocyclotetramerizes to give the macrocycle tetrakis[5,6-di(2-pyridyl)-2,3-pyrazino]porphyrazine, [Py₈TPyzPzH₂], bearing externally four dipyridinopyrazine fragments, reacts with bis(benzonitrile)dichloroplatinum(II), [(C₆H₅CN)₂PtCl₂], in CH₃CN, affording the monometalated species [(CN)₂Py₂PyzPtCl₂]. Single-crystal X-ray work on this compound shows that Pt^II is bound to [(CN)₂Py₂Pyz] through the two pyridine N atoms (“py−py” coordination) in a way similar to that found for its monopalladium analogue, [(CN)₂Py₂PyzPdCl₂]. Cyclic voltammetry of [(CN)₂Py₂PyzPtCl₂] and [(CN)₂Py₂PyzPdCl₂] in nonaqueous media (pyridine, DMSO, and DMF) indicates that the electron-withdrawing effect of the coordinated PtCl₂ and PdCl₂ units results in an initial one-electron reduction (E_1/2 = −0.60 and −0.54 V vs SCE in DMSO, respectively), which is easier by 0.25−0.30 V than the unmetalated [(CN)₂Py₂Pyz] (first reduction: E_1/2 = −0.87 V vs SCE). These electrochemical data are analyzed along with new results for a selected number of related pyrazine and 2,3-dicyanopyrazine molecules as well as earlier reported data on the mono- and bis-N-methylated derivatives [(CN)₂Py(2-Mepy)Pyz]⁺ and [(CN)₂(2-Mepy)₂Pyz]²⁺, with these latter species being formed by reaction of the precursor [(CN)₂Py₂Pyz] with methyl iodide or p-toluensulfonate. The data in this study are also compared to electrochemical data previously reported for a triad of palladium(II) porphyrazine macrocycles obtained from the precursor [(CN)₂Py₂Pyz], i.e., [Py₈TPyzPzPd], the corresponding pentanuclear complex [(PdCl₂)₄Py₈TPyzPzPd] (presenting “py−py” coordination at the dipyridinopyrazine fragments), and the octacation [(2-Mepy)₈TPyzPzPd]⁸⁺ (N-methylated at the pyridine rings). Thin-layer UV−visible spectra of singly reduced [(CN)₂Py₂Pyz]⁻ and its metalated analogues, [(CN)₂Py₂PyzPtCl₂]⁻ and [(CN)₂Py₂PyzPdCl₂]⁻, were measured in pyridine, DMF, and DMSO and show π−π* transitions, as well as unusually intense absorptions in the near-IR region (500−900 nm) of the spectrum.