π-Conjugated zwitterions as paradigm of donor-acceptor building blocks in organic-based materials.

摘要: The very peculiar characteristics of zwitterions, as well a clearand unambiguous definition, have been overlooked in past literature. However, these compounds are particularly important view the impact they had recent and will likely continue to future components performing functional organic hybrid materials. In this Account, we primarily aim define critically concepts zwitterions regarding both their design nomenclature. We focus on specific kind π-conjugated zwitterions. These types systems pertaining class ofdonor-acceptor (push-pull) molecules. ground state, preferentially represented terms an electron donor moiety bearing negative net charge, acceptor one positive charge connected by conjugated bridge. As such, possibly most effective example push-pull structure, possessing relevant features for applications like nonlinear optics, photovoltaics, imaging, high capacitance dielectrics. addition, interaction between dipolar environment is highly can be exploited construction well-organized nanostructures, solution solid state. According Gold Book IUPAC nomenclature, distinction charged molecule called betaine subtle. particular zwitterion onium atom not hydrogen. two often considered equivalent, thus generating confusion while retrieving describe that admitting resonance limiting structures neutral chargeless. For purpose Account benefit researchers striving retrieve materials-related literature data, suggest use term π-zwitterions instead commonly used plain "zwitterions". show definition enables clear identification having unique properties distinct from "dipolar compounds." common groups π-zwitterions. particular, our attention special case nitrile functionality, which tends contiguous charge. also address emphasis benzenoid substituted heteroaromatic units π-zwitterions, because HOMO-LUMO energetic consequences specifically involved cases. make reference paradigmatic second order optical properties. Here, value first hyperpolarizability β versus alternation bond length turns out measure balance chargeless contribution description report collected group others, concerning containing and/or groups, those based acceptors so far described, merocyanines. With merocyanines, how play fundamental role fast growing field photovoltaics. Finally, present made up open new scenarios chemistry.