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A series of luminescent rhenium(I) complexes of 2,2′-bipyridine appended with a coumarin fluorophore has been successfully synthesized and characterized. Their photophysical behavior, ion-binding properties, and fluorescence resonance energy transfer (FRET) behavior from the coumarin donor to the rhenium(I) bipyridyl acceptor were studied. The FRET efficiencies were found to vary upon addition of various metal ions with different sizes due to conformational changes. Their stability constants have been determined by both UV−visible and luminescence spectrophotometric methods.

A series of luminescent branched platinum(II) alkynyl complexes, [1,3,5‐{RCC(PEt3)2PtCCC6H4CC}3C6H3] (R=C6H5, C6H4OMe, C6H4Me, C6H4CF3, C5H4N, C6H4SAc, 1‐napthyl (Np), 1‐pyrenyl (Pyr), 1‐anthryl‐8‐ethynyl (HCCAn)), [1,3‐{PyrCC(PEt3)2PtCCC6H4CC}2‐5‐{(iPr)3SiCC}C6H3], and [1,3‐{PyrCC(PEt3)2PtCCC6H4CC}2‐5‐(HCC)C6H3], was successfully synthesized by using the precursors [1,3,5‐{Cl(PEt3)2PtCCC6H4CC}3C6H3] or [1,3‐{Cl(PEt3)2PtCCC6H4CC}2‐5‐{(iPr)3SiCC}C6H3]. The X‐ray crystal structures of [1,3,5‐{MeOC6H4CC(PEt3)2PtCCC6H4CC}3C6H3] and [1,8‐{Cl(PEt3)2PtC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‐ {RCC(PEt3)2PtCCC6H4C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) (dπ(Pt)→π*(CCR)) character, while the emission origin of the branched complexes with polyaromatic alkynyl ligands, [1,3,5‐{RCC(PEt3)2PtCCC6H4CC}3C6H3] with R=Np, Pyr, or HCCAn, [1,3‐{PyrCC(PEt3)2PtCCC6H4CC}2‐5‐{(iPr)3SiCC}C6H3], [1,3‐{PyrCC(PEt3)2PtCCC6H4CC}2‐5‐(HCC)C6H3], and [1,8‐{Cl(PEt3)2PtCC}2An], was tentatively assigned to be derived from the predominantly 3IL states of the respective polyaromatic alkynyl ligands, mixed with some 3MLCT (dπ(Pt)→π*(C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.

Newly synthesized diethynylcarbazole-bridged platinum(ii) complex 3,6-{ClPt(PEt₃)₂C&z.tbd;C}₂-9-nBuCarb (nBuCarb = n-butylcarbazole) and terpyridyl-containing platinum(ii) alkynyl complex [Pt(tBu₃trpy)(C&z.tbd;CC₆H₄C&z.tbd;CH)]OTf were shown to serve as versatile precursors for the assembly of a novel luminescent tetranuclear platinum(ii) alkynyl complex [3,6-{Pt(tBu₃trpy)(C&z.tbd;CC₆H₄C&z.tbd;C)Pt(PEt₃)₂C&z.tbd;C}₂-9-nBuCarb](OTf)₂. A divergent route can also be applied to synthesize the tetranuclear complex in three steps, involving the use of trimethylsilyl protecting groups on the alkynyl ligand.

The reaction of the starting complex trans-Pd(PEt₃)₂Cl₂ with branched alkynyl ligands, 1,3,5-triethynylbenzene (L1) and 1,3-diethynyl-5-triisopropylsilylethynylbenzene (L2), in the presence of HNEt₂ and copper(I) catalyst led to formation of the respective luminescent branched acetylide complexes, 1,3,5-[Cl(Et₃P)₂PdC&z.tbd6;C]₃C₆H₃ 1 and 1,3-[Cl(Et₃P)₂PdC&z.tbd6;C]₂-5-[(ⁱPr)₃SiC&z.tbd6;C]C₆H₃ 2, which can serve as building blocks for the construction of metallodendrimers either by a divergent or a convergent approach. Photophysical studies of these complexes showed the di- and tri-nuclear palladium complexes 1 and 2 are emissive in EtOH–MeOH (4∶1, v/v) glass at low temperature. Synthesis of the first generation metallodendrimers using 1 as a building block has also been attempted and shows promising results.

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