Abstract
Novel (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) and Pd(II) complexes were prepared by nucleophilic additions of 1,3-diiminoisoindoline to Pt(II) or Pd(II)-bound nitriles, respectively. Photophysical characterization allowed elucidation of the electronic structure of some of the complexes.
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Treatment of trans-[PtCl2(NCR)2] 1 (R=Me (1a), Et (1b), o-ClC6H4 (1c), p-ClC6H4 (1d), p-(HCO)C6H4 (1e), p-O2NC6H4CH2 (1f)) with 1,3-diiminoisoindoline HNCC6H4C(NH)NH 2 gives access to the corresponding (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pt(II) complexes [PtCl{NHC(R)NC(C6H4)NCNC(R)NH}] 3a–f, in good yields (65–70%). The reaction of trans-[PdCl2(NCMe)2] 4a with 2 furnishes (1,3,5,7,9-pentaazanona-1,3,6,8-tetraenato)Pd(II) complex [PdCl{NHC(Me)NC(C6H4)NCNC(Me)NH}] 5a, in good yield (65%). However, the reaction of trans-[PdCl2(NCR)2] 4 (R=Ph (4b), p-MeC6H4CH2 (4c), p-(HCO)C6H4 (4d), p-O2NC6H4CH2 (4e)) with 2 gives a number of unidentified products. The compounds 3a–f and 5a were characterized by IR, 1H, 13C and DEPT-135 NMR spectroscopies, elemental analyses and, in the case of the Pt(II) complex [PtCl{NHC(Me)NC(C6H4)NCNC(Me)NH}] 3a, also by X-ray diffraction analysis. Compounds 3a and 3b were also characterized by UV–Vis absorption and luminescence emission spectroscopies. Emission quantum yields of ca. 3×10−3 were obtained in dichloromethane solution, and luminescence lifetimes are in the order of the tens of nanoseconds. Both compounds also exhibited luminescence in solid state (polystyrene matrix), with luminescence lifetimes in the order of hundreds of nanoseconds.