Unexpected Deformations Induced by Surface Interaction and Chiral Self-Assembly of Co-II-Tetraphenylporphyrin (Co-TPP) Adsorbed on Cu(110): A Combined STM and Periodic DFT Study
Artikel i vetenskaplig tidskrift, 2010

In a combined scanning tunnelling microscopy (STM) and periodic density functional theory (DFT) study, we present the first comprehensive picture of the energy costs and gains that drive the adsorption and chiral self-assembly of highly distorted Co-II-tetraphenylporphyrin (Co-TPP) conformers on the Cu(110) surface. Periodic, semi-local DFT calculations reveal a strong energetic preference for Co-TPP molecules to adsorb at the short-bridge site when organised within a domain. At this adsorption site, a substantial chemical interaction between the molecular core and the surface causes the porphyrin macrocycle to accommodate close to the surface and in a flat geometry, which induces considerable tilting distortions in the phenyl groups. Experimental STM images can be explained in terms of these conformational changes and adsorption-induced electronic effects. For the ordered structure we unambiguously show that the substantial energy gain from the molecule surface interaction recuperates the high cost of the induced molecular and surface deformations as compared with gas phase molecules. Conversely, singly adsorbed molecules prefer a long-bridge adsorption site and adopt a non-planar, saddle-shape conformation. By using a van der Waals density functional correction scheme, we found that the intermolecular pi-pi interactions make the distorted conformer more stable than the saddle conformer within the organic assembly. These interactions drive supramolecular assembly and also generate chiral expression in the system, pinning individual molecules in a propeller-like conformation and directing their assembly along non-symmetric directions that lead to the coexistence of mirror-image chiral domains. Our observations reveal that a strong macrocycle surface interaction can trigger and stabilise highly unexpected deformations of the molecular structure and thus substantially extend the range of chemistries possible within these systems.

metalloporphyrin

metal phthalocyanines

porphyrin molecules

probe microscopy

conformational-changes

ag(111)

density functional calculations

porphyrinoids

copper surface

scanning-tunneling-microscopy

chirality

adsorption

self-assembly

scanning

chemistry

mobility

Författare

P. Donovan

University of Liverpool

A. Robin

University of Liverpool

M. S. Dyer

University of Liverpool

Mats Persson

Chalmers, Teknisk fysik, Material- och ytteori

R. Raval

University of Liverpool

Chemistry - A European Journal

0947-6539 (ISSN) 1521-3765 (eISSN)

Vol. 16 11641-11652

Ämneskategorier

Kemi

DOI

10.1002/chem.201001776