The hows and whys of peculiar coordination of 4-amino-2,1,3-benzothiadiazole

4-Amino-2,1,3-benzothiadiazole (L) and its model complexes with Cu + , Zn 2+ , Ag + and Cd 2+ have been computationally investigated in order to reveal the origins of coordination preferences of this multidentate ligand. The computational description is consistent with the analysis of experimental crystal structures of the coordination compounds described earlier and of two new complexes viz . [ZnL(H 2 O)Cl 2 ] and [CdL 2 (H 2 O) 2 (NO 3 ) 2 ]. Possible coordination types of L are discussed by means of rotational hindrance of NH 2 group, relative thermodynamic stability of the complexes and intramolecular interaction analysis. On the basis of our findings, molecular structure – spectral properties relationships of the complexes are revealed. The results obtained for L are compared with those obtained for 8-aminoquinoline, which is structurally similar to L and is known to form a number of metal complexes.