2011 folder is easy: within Lightroom, in the Folders panel just drag it from the C: to the D: drive. Lightroom will move the files and update its database.
I don't know how many photos you've got in the 2012 folder, but I do regularly encounter a similar scenario. When back-dating scanned photos, I also like to shuffle them into the correct folders. I do this all on my main drive, so I end up with a bunch of old year folders; something like:
Of course, 2012 is my current working folder, and the others are the newly-created folders for the old scans. After I'm done working with the scans I want to get them on my external drive, which has many many years of folders, likely including those I've created.
So in this scenario, within Lightroom, I open the year folder (and the month folder, if I created one) and drag
1980/07/scan.jpg to my external drive's
1980/07/. There are likely many photos to move, so I simply select batches of them to move. This works well for me, but again I don't know how many photos you've got in your 2012 folder.