Luminescent One- And Two-Dimensional Extended Structures anda Loosely Associated Dimer Based on Platinum(II)-Thallium(I)

Resumen

Neutralization reactions between (NBu 4) 2[trans- Pt(C 6F 5) 2(CN) 2] 1 and (NBu 4) 2[cis-Pt(C 6F 5) 2(CN) 2] 2 with TIPF 6 have been carried out, and the resulting structures of [trans,trans,trans-Tl 2{Pt(C 6F 5) 2(CN) 2}·(CH 3COCH 3) 2] n [4·(CH 3COCH 3) 2] n and {Tl[Tl{cis-Pt(C 6F 5) 2(CN) 2}]·(H 2O)} n [5·(H 2O)] n have been determined by X-ray crystallography. Remarkably, the change from trans to cis geometry on the platinum substrate causes a significant decrease in the Pt II⋯ Tl I metallophilic interaction. Thus, the platinum center in the trans fragment easily connects with two Tl I ions forming a distorted pseudo-octahedron PtTl 2, which generates a final two-dimensional layered structure by secondary additional intermolecular Tl I· N(CN) interactions. However, the [cis-Pt(C 6F 5) 2(CN) 2] 2- fragment interacts strongly with just one Tl center leading to an extended helical [-Pt-Tl-Pt-Tl-] n n- chain. In this case, the second thallium center neutralizes the anionic chain mainly through Tl⋯N(CN) (intra) and Tl⋯F(C 6F 5) (intra and inter)teractions. The reaction of TlPF 6 with the monoanionic fragment (NBu 4)[cis-Pt(C 6F 5) 2(CN)(PPh 2C≡CPh)] 3 yields the discrete associated dimer [Tl(cis-Pt(C 6F 5) 2(CN)(PPh 2C≡CPh)}] 2 [6] 2. Dimer [6] 2 could be described as two square pyramids with the thallium atoms in the apical positions, connected through Tl⋯N(cyano) interactions. The final heteropolynuclear Pt-Tl complexes, except 4 at room temperature, show bright emission in the solid state when irradiated with UV-vis radiation, in contrast to the precursors 1 and 3, which are not luminescent. This difference indicates that the emissions in 4-6 are presumably related to the interaction between the metal centers. The Pt-Tl bonding interactions and, consequently, the emissive properties are lost in solution at room temperature, as shown by the conductivity and NMR measurements. However, variable- concentration luminescence measurements in glassy acetonitrile solutions indicate the formation of different aggregates with different degrees of Pt⋯Tl interactions for 4 and 5 and a dimeric structure similar to that observed in solid state for 6. © 2008 American Chemical Society.