Triplet Excited-State Energetics and Dynamics in Molecular “Roller Wheels”

Abstract

We report the photoinduced excited-state dynamics of a series of novel Pt(II)-bisacetylide containing conjugated small molecules that possess geometric shapes resembling "roller wheels," but that differ in lengths of the linear conjugated chromophores, i.e., the "rollers". We measure excited-state evolution and triplet formation by ultrafast pump probe transient absorption followed by quantifying the triplet decay lifetimes using nanosecond flash photolysis transient absorption techniques. Two of these complexes of relatively longer chromophore lengths and smaller bandgaps do not show phosphorescence emission. Thus, the triplet energy is approximated by quenching, utilizing fullerene derivatives with varying lowest unoccupied molecular orbital energies. Furthermore, 3 O 2 quenching experiments are performed to quantify the minimum triplet excitedstate quantum yields for these complexes. Finally, our fullerene and 3 O 2 transient absorption quenching data demonstrate that the estimations of excited-state energies by cyclic voltammetry are not always accurate for these low band-gap organic materials, which require more extensive photophysical studies.

Understanding the Photochemical Properties of Polythiophene Polyelectrolyte Soft Aggregates with Sodium Dodecyl Sulfate for Antimicrobial Activity

“…We believe that this is due to water's ability to assist in the deactivation of triplet excited states, the short lifetime of 1 O 2 in water (3 μs) in comparison to 30−300 μs for organic solvents, and the limitation of our instrumentation in detecting 1 O 2 quantum yield less than 0.2. 53 This observation is partially corroborated by the observation of 1 O 2 emission in DMSO (Figure S21).…”

Unexpectedly Long Lifetime of the Excited State of Benzothiadiazole Derivative and Its Adducts with Lewis Acids

“…To the best of our knowledge, only two works have been reported on purely organic phosphorescent Br-substituted 2,1,3-benzothiadiazoles [ 44 , 45 ], and a few more works have been devoted to organic non-bromine 2,1,3-benzothiadiazoles showing microsecond lifetimes [ 46 , 47 , 48 ]. Metal-containing phosphorescent benzothiadiazoles are more abundant, but examples of metals are predominantly represented by precious Pt(II) [ 49 , 50 , 51 ], Au(III) [ 52 ], Au(I) [ 53 ], Ir(III) [ 54 , 55 ] and Ru(II) [ 56 ].…”

Pt(II)-Bisacetylide ‘Roller Wheels’: Molecular Engineering towards Small Bandgap, High Crystallinity, and Controlled Triplet Exciton Processes

“…For example, we have prepared an ionic fullerene derivative (I-C 60 ) that possesses a lower LUMO level at -3.94 eV when compared with that of C 60 at -3.86 eV (Figure 7). 40 These values are estimated from reduc-…”

“…For example, we have prepared an ionic fullerene derivative (I-C 60 ) that possesses a lower LUMO level at –3.94 eV when compared with that of C 60 at –3.86 eV (Figure 7 ). 40 These values are estimated from reduction onset potentials in solution cyclic voltammetry measurements under identical conditions. Similarly, the HOMO levels of RWPt-2 and RWPt-3 are estimated at –5.0 eV and –4.9 eV, respectively.…”