Larger molecules have smaller HOMO-LUMO Gaps?

  1. Is it true that in general, larger molecules will have smaller HOMO-LUMO gaps?

    In this case consider that we are comparing long vs short saturated molecules,
    and long vs. short conjugated molecules.
  2. jcsd
  3. DrDu

    DrDu 4,636
    Science Advisor

    If it were true in general, there wouldn't be any insulators.
  4. When it comes to chemistry, in general there are no reliable generalities.
  5. DrDu

    DrDu 4,636
    Science Advisor

    In saturated molecules, the gap will hardly depend on system size while in conjugated systems, it will decrease with system size. However, in larger conjugated molecules, new gaps may open due to the Peierls instability.
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