Syntheses, Luminescence Behavior, and Assembly Reaction of Tetraalkynylplatinate(II) Complexes: Crystal Structures of [Pt(tBu3trpy)(C≡CC5H4N)Pt(tBu3trpy)](PF6)3 and [Pt2Ag4(C≡CC≡CC6H4CH3-4)8(THF)4]

Abstract

A series of tetraalkynylplatinate(II) complexes, (NBu 4) 2[Pt(C≡CR) 4] (R = C 6H 4N-4, C 6H 4N-3, and C 6H 3N 2-5), and the diynyl analogues, (NBu 4) 2[Pt(C≡CC≡ CR) 4] (R = C 6H 5 and C 6H 4CH 3-4), have been synthesized. These complexes displayed intense photoluminescence, which was assigned as metal-to-ligand charge transfer (MLCT) transitions. Reaction of (Bu 4N) 2[Pt(C≡CC 5H 4N-4) 4] with 4 equiv of [Pt( tBu 3trpy)(MeCN)](OTf) 2 in methanol did not yield the expected pentanuclear platinum product, [Pt(C≡CC 5H 4N) 4{Pt tBu 3trpy)} 4](OTf) 6, but instead afforded a strongly luminescent 4-ethynylpyridine-bridged dinuclear complex, [Pt( tBu 3trpy)(C≡CC 5H 4N)Pt( tBu 3trpy)](PF 6) 3, which has been structurally characterized. The emission origin is assigned as derived from states of predominantly 3MLCT [d π(Pt) → π* ( tBu 3trpy) character, probably mixed with some intraligand 3IL [π → π*(C≡)], and ligand-to-ligand charge transfer 3LLCT [π(C≡C) → π*( tBu 3trpy)] character. On the other hand, reaction of (Bu 4N) 2[Pt(C≡CC≡ CC 6H 4CH 3-4) 4] with [Ag(MeCN) 4][BF 4] gave a mixed-metal aggregate, [Pt 2Ag 4(C≡CC≡CC 6H 4CH 3-4) 8(THF) 4]. The crystal structure of [Pt 2Ag 4(C≡CC≡CC 6H 4CH 3-4) 8(THF) 4] has also been determined. A comparison study of the spectroscopic properties of the hexanuclear platinum-silver complex with its precursor complex has been made and their spectroscopic origins were suggested.