[AS3] How to convert this from AS2 -> AS3?

programming flash
1

In AS2, i used to write

for(i=0; i<5; i++){
   this.createEmptyMovieClip("menu"+i, i);
   this["menu"+i].alpha = 50;
}

In AS3, i try

public class main extends Sprite{
   public function main() {
      for(i=0; i<5; i++){
         this.["menu"+i] = new MovieClip();
      }
   }
}

but it doesnt work. I get an “Error #1056: Cannot create property menu0 on main.”

Can somebody please help me? Tnx in advance.