While reading about push-pull systems in papers, I came across the term quinoid character. I looked for it in google here is what I've found:
In polyphenylene the ground state is a whole lot of aromatic rings joined together - very stable. Note that the bond joining the phenyls is a single bond. A quinoid state is one where the double bonds have shifted so that there is a double bond where that above single used to be. This is a high energy state.
I still don't get it and what is the purpose of a high quinoid character?