interested to do:对做某事感兴趣,想了解某事。
interested in doing:对某种想法感兴趣,doing 通常为想法。
例句:
I shall be interested to know what happens.
我很想知道发生了什么事。 (想了解)
I'm interested in working in Switzerland. Do you have any idea about that?
我对在瑞士工作感兴趣。你想过这事吗? (一种想法)