Since they can be considered creatures (constructs), can you sunder an intelligent item?
How about animated objects (created via the craft construct feat, so they can still be held)?
I think sunder would still apply. Either that or you can just directly attack them with a regular attack. But since the intelligent item is being wielded its probably easiest to represent its AC using the standard sunder mechanics of the game.
I would say if its being held you can sunder it, if the item is moving around on its own then calculate its AC and you can attack it normally.
Under the construct type the thing is either an animated object or a creature. If your GM treats the sword as an animated object then yes. If they're a creature then no.