Solid-state exciplex emission and logic gate behavior in modified o-carboranes

Introduction: Multiple-stimuli-responsive materials which respond to multiple stimuli such as temperature, vapor, and mechanical pressure, are expected to have applications in next-generation nanoelectronics such as logic gates. Solid-state luminescent dyes, in particular, are expected to be put into practical use, but it was extremely difficult to achieve both luminescence and stimulus responsiveness with conventional dyes. To overcome this challenge, we newly conjured solid-state exciplex emission to o-carborane-modified dyes and constructed molecular logic gates. Materials and methods: Solid exciplex formation was attempted using ball mills with N,N-diethylaniline-modified o-carborane and pyrene derivatives as donor and acceptor units, respectively. The luminescent species of the mixed solid-state luminescent material were assigned using various spectroscopic methods. Two types of inputs, acid and temperature, were used for the molecular logic gate, and the emission wavelength or emission intensity corresponding to each luminescent species was used as outputs. Results: First, we observed exciplex formation from the solid mixture with N,N-diethylaniline-modified o-carborane and pyrene. From the optical measurements, we discovered that treatment of this solid mixture with acid vapor simultaneously quenched exciplex emission and restored the locally excited emission from pyrene. We also found that the solid mixture containing two kinds of o-carborane derivatives, each modified with pyrene and N,N-diethylaniline, exhibited multiple-stimuli-responsive properties to temperature and acid. Finally, we achieved complex molecular logic gate in response to luminescence wavelength or intensity. Conclusions: Based on aryl-modified o-carborane systems, we were able to obtain exciplex emission from a solid sample originating from the donor-acceptor interaction. Furthermore, we were able to construct solid-state luminescent materials that can exhibit logic circuit responses.