Sending manuscript to a journal that rejected an earlier paper
This is perfectly legit. You are not forbidden to submit ever again to a journal that has rejected one of your earlier manuscripts. Indeed, rejections happen for everyone. It is best not to take them too badly.

Now, it would be a different story if you resubmitted the same paper that was previously rejected, or a version with only minor updates. Sending an entirely new manuscript, or a much more mature version, is unproblematic.


  Or is there going to be some bias because of earlier rejections ?


Important journals get many submissions, the majority of which they have to reject. I think it is very unlikely that the responsible editor even remembers that you already had a paper rejected a few years back. And even if (s)he does, it is unlikely that (s)he holds it against you. As I said, rejection is something that happens to every researcher, at least now and then.