The CO ligation to two different ruthenium porphyrins on the Ag(111) surface under vacuum was investigated experimentally and theoretically. The electronic and geometric changes upon ligation, as well as the energetics of the process were elucidated. The surface adaptability of the porphyrin macrocycle conformation proves crucial for CO binding.

Conformational control of chemical reactivity for surface-confined Ru-porphyrins
P. Knecht, J. Reichert, P. S. Deimel, P. Feulner, F. Haag, F. Allegretti, M. Garnica, M. Schwarz, W. Auwärter, P. T. P. Ryan, T.-L. Lee, D. A. Duncan, A. P. Seitsonen, J. V. Barth and A. C. Papageorgiou
Angew. Chem. Int. Edit. (2021)
https://doi.org/10.1002/anie.202104075