A series of platinum(II) terpyridyl alkynyl complexes, [Pt{4′-(4-R¹-C₆H₄)terpy}(CC-C₆H₄-R²-4)]ClO₄ (terpy = 2,2′:6′,2′′-terpyridyl; R¹ = R² = N(CH₃)₂ (1); R¹ = N(CH₃)₂, R² = N-[15]monoazacrown-5 (2); R¹ = CH₃, R² = N(CH₃)₂ (3); R¹ = N(CH₃)₂, R² = H (4); R¹ = CH₃, R² = H (5)), has been synthesized and the photophysical properties of the complexes have been examined through measurement of their UV/Vis absorption spectra, photoluminescence spectra, and transient absorptions. Complex 3 shows a lowest-energy absorption corresponding to a ligand-to-ligand charge-transfer (LLCT) transition from the acetylide to the terpyridyl ligand, whereas 4 shows an intraligand charge-transfer (ILCT) transition from the π orbital of the 4′-phenyl group to the π* orbital of the terpyridyl. Upon protonation of the amino groups in 3 and 4, their lowest-energy excited states are switched to dπ(Pt)π*(terpy) metal-to-ligand charge-transfer (MLCT) states. The lowest-energy absorption for 1 and 2 may be attributed to an LLCT transition from the acetylide to the terpyridyl. Upon addition of an acid to a solution of 1 or 2, the amino group on the acetylide is protonated first, followed by the amino group on the terpyridyl. Thus, the lowest excited state of 1 and 2 can be successively switched from the LLCT state to the ILCT state and then to the MLCT state by controlling the amount of the acid added. Such switches in the excited state are fully reversible upon subsequent addition of a base to the solution. Sequential addition of alkali metal or alkaline earth metal ions and then an acid to a solution of 2 also leads to switching of its lowest excited state from the LLCT state, first to the ILCT state and then to the MLCT state. All of the complexes exhibit a transient absorption of the terpyridyl anion radical, which is present in all of the LLCT, ILCT, and MLCT states. However, the shape of the transient absorption spectrum depends on both the substitution pattern on the terpyridyl moiety and the nature of the excited state.

Bichromophoric compounds BP-C-NP and BP-C-NBD were synthesized with benzophenone chromophore (BP) as the donor, and 2-naphthyl (NP) and norbornadiene group (NBD) as the acceptor, respectively. Their intramolecular triplet energy transfer was examined. The bridges linking the donor and acceptors in these molecules involve a crown ether moiety complexing a sodium ion. Phosphorescence quenching, flash photolysis and photosensitized isomerization experiments indicate that intramolecular triplet energy transfer occurs with rate constants of about 3.3×10⁵ and 4.8×10⁵ s⁻¹ and efficiencies of about 33 and 42 % for BP-C-NP and BP-C-NBD, respectively. Theoretical calculations indicate that these molecules adopt conformations below room temperature which allow their two-end chromophores conducive to through-space energy transfer.

The platinum(II) terpyridyl acetylide complex [Pt(terpy)(CCR)]ClO₄ (terpy=2,2′ : 6′2″-terpyridine, R=CH₂CH₂CH₃) (1) was incorporated into Nafion membranes. At high loading the dry membranes exhibit intense photoluminescence with λ_max at 707 nm from the ³MMLCT state. which was not observed in fluid solution. Upon exposure to the vapor of polar volatile organic compounds (VOC), this photoluminescence was significantly red-shifed. This process was fully reversible when the VOC-incorporated membrane was dried in air. The dramatic and reversible changes in the emission spectra made the Nafion-supported complex as an interesting sensor candidate for polar VOC.

The first intramolecular charge transfer transition based on 2-ureido- 4[1H]-pyrimidinone binding module was reported.