In this proposed collaborative project, the PI's propose a research program poised for understanding the effects of electronic coherence occurring in light-induced super-positioned electronic transitions. Specifically, energy and electron transfer occurring between chromophores in three classes of multi-chromophore synthetic platforms will be investigated using two-dimensional electronic spectroscopy (2DES). These experimental systems are engineered to tune electronic coupling in their excited states, which are either responsible for or can be correlated to electronic coherence originated through in-phase motions of electrons induced by photon excitation. The detection of both electronic and vibronic coherence in these designed molecules will be assessed using broadband 2DES featuring ~6 femtosecond time resolution; this time window encompasses both electronic and vibronic coherence. The measured coherences will be correlated with the observation of photoinduced intramolecular energy and/or electron transfer chemistry and rationalized using continuously developing theory to assess the role of electronic and/or vibronic coherence in these fundamental primary processes related to light activation. Three specific molecular designs are targeted for these ~6 fs 2DES investigations: (1) next generation Pt(II) dimers bridged by hydroxypyridines featuring metal-metal-to-ligand charge transfer (MMLCT) excited states where a metal-metal bond is transiently formed following light excitation; (2) Pt(II) dimers whose terminal cyclometalating ligands are decorated with bay-substituted naphthalenediimide (NDI)-based energy and/or electron acceptors; and (3) co-facial (dimer) or linear (dimer and trimer) constructs featuring NDI subunits that can be adjusted with respect to their relative distance, orientation, bond connectivity, and energetics, yielding systematically varied electronic coupling. The photogenerated energy and electron transfer reactions in these multi-chromophore systems will be tracked and correlated with the strength of electronic coherence to evaluate their influence on these photochemical processes. The proposed project seeks to glean new insight into excited state chemistry and how this knowledge can leveraged to control reactivity in condensed phases, molecular photonics, and photocatalysis.
|Effective start/end date||8/15/20 → 7/31/23|
- National Science Foundation (CHE 1955806)