2, Lancaster University, Lancaster, , United Kingdom
The conformation of a molecule determines its chemical and physical characteristics. Consequently, changes in molecular conformation modify important properties such as molecular conductance, chemical activity and assembly. Clear identification of the conformational structure is therefore crucial for understanding these properties. Whilst submolecular resolution imaging with non-contact atomic force microscopy (nc-AFM) has provided unparalleled insight into many interesting molecular systems [1,2], non-planar molecular structures have proved far more challenging. Here I will discuss studies on tetra(4-bromophenyl)porphyrin (Br4TPP) molecules deposited onto a Cu(111) surface, which are known to adopt two distinct non-planar conformations. Using nc-AFM we are able to unambiguously determine the adsorption configuration of porphyrin conformers on the Cu(111) surface with submolecular detail. We show through direct measurement that the lateral forces required to manipulate each conformer significantly differ , suggesting unusually strong binding arising from vdW interactions that consequently dramatically affect the molecular density of states . Following this, I will discuss the perceived limits of imaging molecules with non-planar structure and the potential to achieve single bond resolution outside of UHV conditions as a general analytical tool.  Jarvis, S.P. Jarvis. Int. J. Mol. Sci., 2015, 16, 19936.  N Pavlicek and L. Gross. Nature Reviews Chemistry, 2017, 1, 0005.  Jarvis, S. P. et al, Nature Commun. 2015, 6, 8338.  Jarvis, S. P. et al, J. Phys. Chem. C 2015, 119, 27982.