Tri-[Pt2TI]3- and polynuclear chain [Pt-TI]∞- complexes based on nonbridged PII-TII bonds:: Solid state and frozen solution photophysical properties

Treatment of (NBU4)(2)[PtR4] (R = C6F5) with 1 or 0.5 equiv of TINO3 in EtOH/H2O produces colorless crystals of trinuclear complex (NBu4)(3)[Tl{PtR4}(2)],1, in which the Tl+ center is complexed by two [PtR4](2-) fragments (Pt-Tl = 2.9777(4) and 3.0434(4) angstrom). The expected mixed complex with a Pt/Tl composition of 1:1, 2, is generated as an orange microcrystalline solid by treating [PtR4](2-) with a large excess of TINO3 (similar to 8 equiv). Crystallographic analysis of 2 reveals the formation of a novel one-dimensional (1 D) heterometallic linear chain (NBu4)(infinity)[Tl{PtR4}](infinity), 2, formed by alternating a [PtR4](2-) fragment and a Tl+ center with a uniform Pt-Tl bond separation along the chain of 3.0321(2) angstrom. Surprisingly, treatment of (NBu4)(2)[PtR4] with 1 equiv of TIPF6 in EtOH yields pale greenish-yellow needles of an unusual adduct, 2 center dot(NBu4)(PF6)}(infinity) (3), which was found to form a similar extended linear chain, {TIPtR4}(infinity), constructed by two alternating Pt-Tl separations, a shorter (3.1028(6) angstrom) one and a longer (3.2306(6) angstrom) one. The solid state and solution photophysical properties have been examined. While complex 1 shows a high-energy MM'CT blue phosphorescence (450 nm), the extended chain in 2 exhibits a lower-energy emission (582 nm) than that in adduct 3 (505 nm). For products 2 and 3, interesting luminescence thermochromism is observed in frozen solutions. The emissions are found to be strongly dependent on the solvent, concentration, and excitation wavelength.