C-G-Bb-D-Db-G
I know that the C-G-Bb is a C11 chord just don't know what the D-Db-G makes it become.
Actually, C-G-Bb is really more of a C7 chord, ur just missing the 3rd. All in all, it looks and sounds like some kind of sus 7th chord. I'm not sure of this, but my best guess is a C7sus2b9 chord. The sus2 is for the D, which I hope would resolve to E to give you a 3rd for the chord, and make it a C7b9 chord. I hear this as a 5 in F.