Abstract
Bond breaking and forming are essential components of chemical reactions. Recently, the structure and formation of covalent bonds in single molecules have been studied by non-contact atomic force microscopy (AFM). Here, we report the details of a single dative bond breaking process using non-contact AFM. The dative bond between carbon monoxide and ferrous phthalocyanine was ruptured via mechanical forces applied by atomic force microscope tips; the process was quantitatively measured and characterized both experimentally and via quantum-based simulations. Our results show that the bond can be ruptured either by applying an attractive force of ~150 pN or by a repulsive force of ~220 pN with a significant contribution of shear forces, accompanied by changes of the spin state of the system. Our combined experimental and computational studies provide a deeper understanding of the chemical bond breaking process.
Highlights
Bond breaking and forming are essential components of chemical reactions
The ability to obtain images of organic molecules with atomic resolution was first demonstrated by Gross et al in 2009 by using a carbon monoxide (CO) molecule attached to an Atomic Force Microscope (AFM) tip[1] mounted on a qPlus sensor[2]
This characterization is confirmed by comparing with atomic force microscopy (AFM) images of ferrous phthalocyanine (FePc) molecules on the surface Fig. 1c, and further verified by our simulated images (Fig. 1d, e)
Summary
Bond breaking and forming are essential components of chemical reactions. Recently, the structure and formation of covalent bonds in single molecules have been studied by noncontact atomic force microscopy (AFM). The dative bond between carbon monoxide and ferrous phthalocyanine was ruptured via mechanical forces applied by atomic force microscope tips; the process was quantitatively measured and characterized both experimentally and via quantum-based simulations. This work inspired a wide range of applications, including directly characterizing molecular structures[3,4,5], probing molecular properties[6,7,8,9,10], creating new structures[11,12], and even providing a tool for studying various types of chemical bonds, such as hydrogen bonds and halogen bonds[13,14] These studies stimulated significant discussions on the contrast mechanism of AFM images and on the extent to which the image could represent a physical description of a chemical bond[15,16]. This work advances understanding of the origins of measured forces in dative bond breaking
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