How to describe a situation in which you "throw things at the wall and see what sticks" in a master thesis
It would be best to explain why such experiments were conducted along with supporting concepts that you would like to verify. It ought not to look like a random set of trials.

You may write something like this:


  Concept X follows from [explanation of X]. This concept formed the hypothesis Y to justify the following experiments. ... Although the experimental results were negative, it would be of worth to note them here as to why they were so.