Cooperative and diminutive interplay between the hydrogen bonding and halogen bonding in ternary complexes of HCCX (XÂ =Â Cl, Br) with HCN and HNC

► Cluster with dual role of central molecule as electron and proton donor is cooperative. ► When central molecule acts as double electron acceptor, cluster is diminutive. ► Linear correlations between cooperativity and cluster parameters are established. ► Our findings are useful in molecular recognition, and crystal engineering.