We present our recent efforts to illuminate photophysics and photochemistry of organic/inorganic hybrid materials as well as the structure-dynamics relationships that underlie their photoresponsive behaviors.  This talk will focus on photoresponses in two types of hybrid structures:<br/> <br/>(a)   Photoinduced electron transfer in σ-π hybrid organosilanes:  σ-conjugated silanes offer new opportunities for manipulating charge polarization and transport as well as non-linear optical properties of materials. We present the photophysics of hybrid structures in which an electron-rich silane core is flanked by electron-deficient organic acceptors. Based on a detailed characterization using both steady state and ultrafast (transient absorption and Raman) spectroscopies we illustrate that asymmetric charge separation occurs directly with light absorption to create dipolar emissive states. We show that excited-state symmetry breaking that gives rise to asymmetric intramolecular charge transfer is associated with the conformation of the central Si chain. In contrast, ultrafast solvent reorganization or solvent-controlled intramolecular dynamics that typically direct charge localization in rigid organic analogues only serve to stabilize nascent dipolar excited states, rather than induce charge separation from an initial quadrupolar state.<br/>(b) Photocyclization of borazine-core polyaromatics:  Boron-nitrogen doping of polyaromatic hydrocarbons and nanographene presents possibilities for tuning their electronic properties while preserving their structural characteristics. Many pure hydrocarbon multicycles can be synthesized photochemically; in contrast, very little is known about the photochemistry for making their BN-doped counterparts.  We present results of fs-to-μs time-resolved spectroscopic studies on the photophysics and photochemistry of hexaphenyl borazine and other borazine-core structures that probe how BN-doping impacts the efficacy for photochemical C-C bond formation via 6π electrocyclization as well as the stability of resulting cyclized structures. We find that the polarized BN bonds of the borazine greatly compromises the stability of cylized intermediate structures relative to their pure hydrocarbon analogs, but that there may be potential for photochemistry of some BN-doped polyaromatics if it is possible to overcome energetic barriers in the excited state.<br/>

Ultrafast investigations of photoinduced electron transfer and bond formation in organic/inorganic hybrid materials

256th National Meeting (2018)

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