负责 is a verb. that means "to be responsible for (sth)" or "in charge of sth." and 责任 is a noun that means “responsibility” in fact , 负责=(背)负to bear +责(任)responsibility=take responsibility ( for (doing) sth) hope that i have made that clear.

simplily. 負責 is works as verb 責任 works as noun

in this word 负=verb= take ,责= 责任=duty,means have some responsibility[or duty] for something 负责 = take responsibility for something

We use 责任 as noun . For example : 我对此承担责任。 这是你的责任。 We use 负责 as verb or as adj . verb :我负责销售。 adj： 他很负责。 = 他很有责任心。 adj: