The ligand (2-[4-(2,1,3-benzothiadiazole)imino]methyl-phenol) HL1 containing the electron poor benzothiadiazole (BTD) unit, conveniently prepared by condensation of 4-amino-2,1,3-benzothiadiazole and salicylaldehyde, has been structurally characterized single crystal X-ray diffraction. Two energy minima have determined, DFT calculations, for its ortho-vanillin analogue HL2, corresponding either...