However, Mustafa Dogru has hinted Liverpool are also interested.
"When (Arsenal chief) Sven Mislintat was still in Dortmund, he was the first in Germany to watch Caglar," he said. "There's been negotiations, but we still have to agree on the sums. We'll see what happens.
"The only thing I can say about Liverpool is that there are four or five clubs in England watching him."
He added: "The interest is not surprising. Caglar is a modern defender and Freiburg was very important to his development. He has made it to the next level and is now ready for a new challenge."