How can I improve the peak shape of a bipyridine peak? I know it is a complexing agent and that this is the likely cause of the problem (metal ions in stationary phase). I've tried adding EDTA and will soon try a copper salt. Conventional fixes for peak shape/tailing (addition of TEA etc) don't work. Am I on the right track or is the another (better) approach?

I would try one of the new columns with an inbedded amide polar group. This might help shield your compound from interacting with the base silica. I don't have any experience with bipyridine but have had good luck with other amines.

Bipyridine can also undergo strong intramolecular interaction via "aromatic stacking" interactions. See this link:
http://www.molec.com/electrochemistry/notes/Bipyridine/bipy.html
Maybe this is causing some secondary interactions that is causing a distortion of your peak shape. I might try as high an organic concentration as the seperation would tolerate, or perhaps the additon of an aromatic solvent. My best advise is to wait for someone that knows something to post.

Engelhardt and Lobert used bipyridine to measure the metal contamination of columns. Specifically they used the ratio of the retention factors or the ratios of the tailing factors between 2-2' and 4-4' bipyridine.
Assuming you are using the 2-2' BP, this means that your tailing will depend on the metal contamination of your column, which is fairly much unavoidable usng a stainless steel instrument with stainless steel columns and stainless steel frits. You may be on the right track adding metal to your mobile phase, lots of it...