Tomorrow I am giving a seminar, "Essential state models for fluorescent protein chromophores and methine dyes," in the Chemistry department at Parma University, Italy. Here is the current version of the slides.
My host is Anna Painelli. Over the past few years she and her collaborators have done some very nice work showing that the optical properties of a diverse range of complex chromophores can be described by "essential state models" that are effective Hamiltonians acting on a just a few valence bond states. These models include dominant molecular vibrations and the effect of the solvent.
For example, an earlier post mentioned their work on crystal violet.
This work nicely complements work done by Seth Olsen giving a rigorous quantum chemical justification for such essential state models, as in this J. Chem. Phys. paper.