Quote Originally Posted by Photo Engineer View Post

With few exception (Erythrosine and Chlorophyll being two I can name OTOMH), emulsion sensitizing dyes have positively charged Nitrogen atoms in them.

See attached. There is a resonance plus charge carried by one of the Nitrogens as the electrons resonate. Compare with Rhodamine.

Ok Ron, here is rhodamine 6G and B's structure. And I included the one you posted, which is....? Are those just "cyanines"?

This is a completely foreign language to me, but I'd like to learn it. What do you call these kinds of diagrams?