I can't quite tell what the subjects is. You said a sunset, so my mind is naturally going to look for a the sun, which is not visible in the frame.
What are you trying to go for here, something expiremental? I do find the black building interesting, but I still find myself trying to find the sun. I'm in no way trying to shoot you down for this photo, but I can't tell what you are going for.
Also, yes, your camera sensor and/or lens is very dirty.