New dicyano cyclometalated compounds containing Pd(II)-Tl(I) bonds as building blocks in 2D extended structures: Synthesis, structure, and luminescence studies

摘要

New mixed metal complexes [PdTl(C ~λN)(CN) _2] [C ~λN = 7,8-benzoquinolinate (bzq, 3); 2-phenylpyridinate (ppy, 4)] have been synthesized by reaction of their corresponding precursors (NBu _4)[Pd(C ~λN)(CN) _2] [C ~λN = bzq (1), ppy (2)] with TlPF _6. Compounds 3 and 4 were studied by X-ray diffraction, showing the not-so-common Pd II-Tl I bonds. Both crystal structures exhibit 2-D extended networks fashioned by organometallic "PdTl(C ~λN)(CN) _2" units, each one containing a donor-acceptor Pd~(II)-Tl~(I) bond, which are connected through additional Tl?N≡C contacts and weak Tl·π (bzq) contacts in the case of 3. Solid state emissions are red-shifted compared with those of the precursors and have been assigned to metal-metal-to-ligand charge transfer (MMLCT [d/s σ*(Pd,Tl) → π * (C λN)]) mixed with some intraligand (~3IL[π(C ~λN) → π * (C ~λN)]) character. In diluted solution either at room temperature or 77 K, the Pd-Tl bond is no longer retained as confirmed by mass spectrometry, NMR, and UV-vis spectroscopic techniques.