Adsorption structure of macrocyclic energetic molecule DOATF on Au(111)

Furazan macrocyclic compound 3,4:7,8:11,12:15,16-tetrafurazan-1,9-dioxazo-5,13- diazocyclohexadecane (DOATF) is an ideal energetic material with high heat of formation. Here, using scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM), we investigated the adsorption structure of DOATF molecules on Au(111) surface, which shows the four furanzan rings in the STM images and a bright protrusion off the center of the molecule in the nc-AFM images. Combined with density functional theory (DFT) calculations, we confirmed that the bright feature in the nc-AFM images is an N–O coordinate bond pointing upwards in one of the two azoxy groups; while the other N–O bond pointing towards the Au(111) surface. Our work contributes for a deeper understanding of the adsorption structure of macrocyclic compounds, which would promote the designing of DOATF-metal frameworks.