Heteropolynuclear Pt(II)鈥揗(I) Clusters with a CNC Biscyclometalated Ligand

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• 作者：Sara Fuertes ; Christopher H. Woodall ; Paul R. Raithby ; Violeta Sicilia
• 刊名：Organometallics
• 出版年：2012
• 出版时间：June 11, 2012
• 年：2012
• 卷：31
• 期：11
• 页码：4228-4240
• 全文大小：628K
• 年卷期：v.31,no.11(June 11, 2012)
• ISSN：1520-6041

文摘

The mononuclear complex [(EtO₂C-CNC)Pt(dmpyz)] (1) (dmpyz = 2,5-dimethylpyrazine) has been synthesized by reaction of [(EtO₂C-CNC)Pt(dmso)] (A) with dmpyz in a 1:1 molar ratio in dichloromethane. Complex 1 is the precursor for preparing the homodinuclear complex [{(EtO₂C-CNC)Pt}₂(渭-dmpyz)] (2) and the heterotrinuclear clusters [{(EtO₂C-CNC)Pt(dmpyz)}₂M]X (M = Cu, X = PF₆ (3); M = Ag, X = BF₄ (4)). Compounds 1, 2, and 4 were studied by X-ray diffraction methods. In the crystal packing of 1 and 2, the molecules display short intermolecular 蟺路路路蟺 contacts, which control the solid-state emissive behavior. X-ray study on 4 shows two [Pt₂Ag] sandwich-type clusters in the asymmetric unit, both with the two square-planar 鈥?R-CNC)Pt(dmpyz)鈥?moieties stabilized by two Pt 鈫?Ag donor鈥揳cceptor bonds as well as by 畏¹- and 畏²-Ag鈥揅 interactions. Intramolecular 蟺鈥撓€ contacts were found between the pyridine rings of the CNC ligands within the same Pt₂Ag cluster. ¹H and ¹⁹⁵Pt NMR studies confirm that the Pt₂M cluster is also retained in solution at room temperature. ¹⁹⁵Pt NMR spectra of 3 and 4 show signals shifted significantly downfield when comparing with that for the monomer (1), which is attributed to the presence of Pt鈥揗 dative bonds. At lower temperatures (T = 193 K), the copper derivative definitely falls apart, whereas the silver one still holds up unbroken. In the solid state at 77 K, compounds 1鈥?b>4 give red emissions arising from ³蟺蟺 excited states due to the intra- or intermolecular 蟺鈥撓€ contacts observed in the crystal structures. As expected, in glassy solutions (77 K), compound 3 displays analogous emissions to those from the starting material (1). Complexes 1 and 2 show structured emission bands that are particularly sensitive to the 位_ex (HE and LE). In contrast, 4 displays an unstructured emission at 680 nm with a shoulder at 556 nm; both are not dependent on the 位_ex. DFT and TDDFT computational studies have been performed on 1 and 2, which support the conclusions drawn from the photophysical studies.