Serse Cosmi was sacked on Sunday evening and ex-Sampdoria boss Iachini brought in on Monday.
"This opportunity arrived, the club showed great admiration for the work I've done and I am happy," Iachini told Sky Sport Italia.
"It's a shame for Cosmi, who is a friend, but football is like that for us. We are starting from a difficult position in the table, but we are here to work and put all our efforts on to the field.
"In tactical terms we will try to bring some of our ideas. The situation is not easy, but with enthusiasm and hard work we can emerge from it.
"This side has the potential to achieve safety, score more goals and make fewer mistakes."