Certain materials and molecular systems can facilitate coherent electron transport at efficiencies beyond traditional methods. These processes have the potential to minimize energy losses and make photovoltaic and other electronic devices more efficient. Recently, signatures of coherent, recurrent electronic motion were identified in the femtosecond pump-probe spectra of a bi-nuclear platinum complex. This work suggested that the inter-platinum distance modulates the beating in the transient absorption anisotropy and the ability of the system to support coherent electron transfer at all. The bond distance can also be tuned by chemical modification of the bridging ligands, offering a convenient means of controlling charge transfer in these systems. More information about the underlying mechanism enabling this charge transfer can be determined with real-time simulations. Real-time time-dependent density functional theory (RT-TDDFT) was used to model charge transfer in several bi-nuclear platinum complexes for which there was not yet experimental transient absorption anisotropy data. At shorter Pt-Pt distances the two halves of the bi-chromophoric system are strongly coupled and can support coherent electron transfer between them. However, having so many strongly coupled states also leads to a quick loss of phase coherence. Systems with longer Pt-Pt distances lead to charge localization on one side of the system are not able to support charge transfer to the other side. Fortunately, there is an intermediate regime where the two halves are coupled and the loss of phase coherence is mitigated, so the observation of long-lived charge transport is possible. Vibration of the Pt-Pt bond will alter the coupled between the two halves of the system and thus modulate the period of charge transport across the system. This effect and the potential of electron-nuclear coherences were investigated with Ehrenfest coupled electron-nuclear dynamics.

Controlling coherent electron transfer in bi-nuclear platinum complexes

253rd National Meeting (2017)

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