[Nicole]

I would say that this is one of those times where time of day can be extremely important. Granted, light and time of day is always important, but more so when you have a really large subject that can't be lit up using extra lights. I'd try to wait until the time of day where the sun is hitting the side of the building you want to photograph rather than waiting until it's behind it. Or you can use a polarizing filter to allow a slightly longer exposure. Or you can fix it in photoshop as you said.