Novel Luminescent Mixed-Metal Pt-Tl-Alkynyl-Based Complexes: The role of the alkynyl substituents in the metallophillic and eta2(pi...Tl) Bonding Interactions

Abstract

A novel series of [PtTl2(C≡CR)4]n (n = 2, R = 4-CH3C6H4 (Tol) 1, 1-naphthyl (Np) 2; n = ∞, R = 4-CF3C6H4 (Tol F) 3) complexes has been synthesized by neutralization reactions between the previously reported [Pt-(C≡CR)4]2- (R = Tol, TolF) or novel (NBu4) 2[Pt(C≡CNp)4] platinum precursors and Tl 1 (TlNO3 or TlPF6). The crystal structures of [Pt2Tl4(C≡C-Tol)8]·4acetone, 1·4acetone, [Pt2Tl4(C≡CNp) 8]·3 acetone·1/3, H2O, 2·3 acetone ·1/3H2O and [{PtTl2(C≡CTolF) 4}(acetone)S]∞ (S = acetone 3a; dioxane 3b) have been solved by X-ray diffraction studies. Interestingly, whereas in the tolyl (1) and naphthyl (2) derivatives, the thallium centers exhibit a bonding preference for the electron-rich alkyne entities to yield crystal lattices based on sandwich hexanuclear [Pt2Tl4(C≡OR) 8] clusters (with additional Tl⋯acetone (1) or Tl⋯naphthyl (2) secondary interactions), in the C6H 4CF3 (TolF) derivatives 3a and 3b the basic PtII center forms two unsupported Pt-Tl bonds. As a consequence 3a and 3b form an extended columnar structure based on trimetallic slipped PtTl2(C≡CTolF)4 units that are connected through secondary Tl⋯(η2-acetylenic) interactions. The luminescent properties of these complexes, which in solution (blue; CH 2Cl2 1,2; acetone 3) are very different to those in solid state (orange), have been studied. Curiously, solid-state emission from 1 is dependent on the presence of acetone (green) and its crystallinity. On the other hand, while a powder sample of 3 is pale yellow and displays blue (457 nm) and orange (611 nm) emissions, the corresponding pellets (KBr, solid) of 3, or the fine powder obtained by grinding, are orange and only exhibit a very intense orange emission (590 nm). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.