Those with dark leaves do well in sun. Obsidian and Midnight Rose are two that I have that are in full sun and do very well. Lighter leaved varieties tend to burn in full sun. Green leaved varieties, with or without colored veining, do well too. Green Spice is another I have in full sun that does well.

I have my Fire Alarm and Berry Smoothie in direct afternoon sun. I'm in zone 5b. I hardly watered them last year (oops!) and they did great.

Emily, the clematis want even moisture rather than shade for their roots, so mulch will work well, though the Heucheras won't cause problems for the clematis.

I have snow angel in sun from 1 to 4 it bloomed from june to mid july. Zone 4.

i almost bought a marble yesterday to replace sweet tea that died this year. but i will have to thin out my palace purple as its taking over the bed.

i have a heucheralla eclipse in sun from 1 to 4 its doing well.