Chalk Hill has a list of clematis that do well on north walls and shadier locations. It is linked below.

Here is a link that might be useful: Shady clematis

That's a good link to follow. In my own experience, I have a lot that perform reasonable well in those conditions in z5. Narrowing my list to purple, these work well for me:

Madame Grange (a late bloomer than most)
Viticella species
Etoile Violet
Polish Spirit
Warsaw Nike

These are also all type 3's: trim them to the ground in late winter, making clean up of the arbor easy.