Room-temperature phosphorescence and energy transfer in luminescent multinuclear platinum(II) complexes of branched alkynyls

A series of luminescent branched platinum(II) alkynyl complexes, 1,3,5-{RCtriple bond]C(PEt3)2PtCtriple bond]C-C6H4Ctriple bond]C}3C6H3] (R=C6H5, C6H4OMe, C6H4Me, C6H4CF3, C5H4N, C6H4SAc, 1-napthyl (Np), 1-pyrenyl (Pyr), 1-anthryl-8-ethynyl (HCtriple bond]CAn)), 1,3-{PyrCtriple chemical bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}2-5-{(iPr)3SiCtriple bond]C}C6H3], and 1,3-{PyrCtriple bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}2-5-(HCtriple bond]C)C6H3], was successfully synthesized by using the precursors 1,3,5-{Cl(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}3C6H3] or 1,3-{Cl(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}2-5-{(iPr)3SiCtriple bond]C}C6H3]. The X-ray crystal structures of 1,3,5-{MeOC6H4Ctriple bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}3C6H3] and 1,8-{Cl(PEt3)2PtCtriple bond]C}2An] have been determined. These complexes were found to show long-lived emission in both solution and solid-state phases at room temperature. The emission origin of the branched complexes 1,3,5-{RCtriple bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}3C6H3] with R=C6H5, C6H4OMe, C6H4Me, C6H4CF3, C5H4N, and C6H4SAc was tentatively assigned to be derived from triplet states of predominantly intraligand (IL) character with some mixing of metal-to-ligand charge-transfer (MLCT) (dpi(Pt)-->pi*(Ctriple bond]CR)) character, while the emission origin of the branched complexes with polyaromatic alkynyl ligands, 1,3,5-{RCtriple bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}3C6H3] with R=Np, Pyr, or HCtriple bond]CAn, 1,3-{PyrCtriple bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}2-5-{(iPr)3SiCtriple bond]C}C6H3], 1,3-{PyrCtriple bond]C(PEt3)2PtCtriple bond]CC6H4Ctriple bond]C}2-5-(HCtriple bond]C)C6H3], and 1,8-{Cl(PEt3)2PtCtriple bond]C}2An], was tentatively assigned to be derived from the predominantly 3IL states of the respective polyaromatic alkynyl ligands, mixed with some 3MLCT (d(pi)(Pt)-->pi*(Ctriple bond]CR)) character. By incorporating different alkynyl ligands into the periphery of these branched complexes, one could readily tune the nature of the lowest energy emissive state and the direction of the excitation energy transfer.