Dynamics of the Triplet State of a Dithiophene in Different Solid Matrixes Studied by Transient and Pulse EPR Techniques

Abstract

The photoexcited triplet state of a 4-4'-disubstituted dithiophene has been investigated by time-resolved electron paramagnetic resonance in two different solid matrixes-glassy toluene which acts as an amorphous isotropic medium and a spirocyclophosphazene inclusion compound-which provides an ordered confining structure to the guest molecules. Different spectral line shapes with different temperature dependence have been obtained using continuous-wave or spin-echo detection. This behavior was attributed to spin relaxation due to modulation of the zero-field splitting tensor induced by fast librational motion of the dithiophene triplet. Moreover, differences between line shapes in the two matrixes were reproduced considering a librational motion occurring preferentially around different molecular axes

Probing the Wave Function and Dynamics of the Quintet Multiexciton State with Coherent Control in a Singlet Fission Material

“…Modulation of the zero-field splitting tensor by molecular vibrations or triplet exciton hopping is a further possible source of decoherence. However, we expect this mechanism to produce spectral distortions from orientation-dependent decoherence, which we do not observe [39,40]. A further contribution to decoherence could arise from the presence of charges, something which would be interesting to investigate in future studies through, for example, the controlled incorporation of dopants or generating quintet and triplet states in a device architecture [41,42].…”

Insight into the drastically different triplet lifetimes of BODIPY obtained by optical/magnetic spectroscopy and theoretical computations

“…At room temperature, the SLR is fast because Brownian motion in solution can induce modulation of the electron-electron fine interaction. 38,56 Modulation of both secular and pseudo-secular interactions produce electron spin TSLR relaxation, 57 and, analogously, modulation of the dipolar interaction with typical D-values of the order of 10 3 MHz (see next section) can induce an efficient re-equilibration of the three sublevels if TSLR is shorter than the electronic triplet excited state lifetime. In this case only mono-exponential decay kinetics (an averaged decay) can be detected with the ns TA spectroscopy, 42 whereas this different decay kinetics are detectable at 77 K in frozen solution.…”

A slow relaxing species for molecular spin devices: EPR characterization of static and dynamic magnetic properties of a nitronyl nitroxide radical

“…7) was obtained leaving as free parameters the orientation of the axis d and the amplitude a of the rotation angle, on the basis of typical correlation times s L for low-amplitude librational motions. 42 The calculations were performed using a homewritten software, which evaluates the resonance field shift due to the libration making use of second-order perturbation theory. 41,43 The best fitting between calculated and experimental profiles was found for an orientation of the axis d tilted by 24 from the z towards the y axis of the g tensor eigenframe (see Fig.…”