These are stunning crepe myrtles (I have a couple of pictures in the data base). Mine is called: Crape Myrtle (Lagerstroemia Black Diamond® Mystic Magenta™)
I just love those dark (almost black leaves). I've had this plant -- it's still a small tree -- since early summer of 2014 -- and I live a block from the beach.
IF I win one -- I will stay up all night (two if necessary) to find a spot for another one !