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Dinuclear d 8 Pt( ii ) complexes, where two mononuclear square planar Pt( ii ) units are bridged in an “A-frame” geometry, possess photophysical properties characterised by either metal-to-ligand-(MLCT) or metal–metal–ligand-to-ligand charge transfer (MMLCT) transitions determined by the distance between the two Pt( ii ) centres. When using 8-hydroxyquinoline (8HQH) as the bridging ligand to construct novel dinuclear complexes with general formula [C^NPt(μ-8HQ)] 2 , where C^N is either 2-phenylpyridine (1) or 7,8-benzoquinoline (2), triplet ligand-centered ( 3 LC) photophysics results echoing that in a mononuclear model chromophore, [Pt(8HQ) 2 ] (3). The lengthened Pt–Pt distances of 3.255 Å (1) and 3.243 Å (2) results in a lowest energy absorption centred around 480 nm assigned as having mixed LC/MLCT character by TD-DFT, mirroring the visible absorption spectrum of 3. Additionally, 1 and 2 exhibit 3 LC photoluminescence with limited quantum yields (0.008) from broad transitions centred near 680 nm. Photoexcitation of 1–3 leads to an initially prepared excited state that relaxes within 15 ps to a 3 LC excited state centred on the 8HQ bridge, which then persists for several microseconds. All the experimental results correspond well with DFT electronic structure calculations. 

The steady-state and ultrafast to supra-nanosecond excited state dynamics of fac -[Re(NBI-phen)(CO) 3 (L)](PF 6 ) (NBI-phen = 16H-benzo[4′,5′]isoquinolino[2′,1′:1,2]imidazo[4,5- f ][1,10]phenanthrolin-16-one) as well as their respective models of the general molecular formula [Re(phen)(CO) 3 (L)](PF 6 ) (L = PPh 3 and CH 3 CN) has been investigated using transient absorption and time-gated photoluminescence spectroscopy. The NBI-phen containing molecules exhibited enhanced visible light absorption with respect to their models and a rapid formation (<6 ns) of the triplet ligand-centred (LC) excited state of the organic ligand, NBI-phen. These triplet states exhibit an extended excited state lifetime that enable the energized molecules to readily engage in triplet–triplet annihilation photochemistry. 

In this work, a series of eight similarly structured perinone chromophores were synthesized and photophysically characterized to elucidate the electronic and structural tunability of their excited state properties, including excited state redox potentials and fluorescence lifetimes/quantum yields. Despite their similar structure, these chromophores exhibited a broad range of visible absorption properties, quantum yields, and excited state lifetimes. In conjunction with static and time-resolved spectroscopies from the ultrafast to nanosecond time regimes, time-dependent computational modeling was used to correlate this behavior to the relationship between non-radiative decay and the energy-gap law. Additionally, the ground and excited state redox potentials were calculated and found to be tunable over a range of 1 V depending on the diamine or anhydride used in their synthesis ( E red * = 0.45–1.55 V; E ox * = −0.88 to −1.67 V), which is difficult to achieve with typical photoredox-active transition metal complexes. These diverse chromophores can be easily prepared, and with their range of photophysical tunability, will be valuable for future use in photofunctional applications.