Probing microcluster formation between PACO and solvents containing oxygen donor sites mediated by the 'N-H' Bond

► Formation of hydrogen bonded 1:1 molecular cluster by PACO with various solvents has been investigated. ► N-H bond length and N-H stretching frequency of PACO change due to microhydration. ► Change in N-H bond length and frequency have been modeled using Kamlet-Taft analysis. ► Experimental IR spectrum of PACO indicates cooperative strengthening of H-bonding.