Scanning tunneling microscopy was used to visualize a four-component two-dimensional crystal formed at a liquid-solid interface. Simply mixing the four components and applying it to a graphite surface led to spontaneous self-assembly of the crystal. The presence of selected guest molecules induced a structural transformation of the host network from non-porous to porous by co-adsorbing inside the formed pores. Both hydrogen bonding and van der Waals interactions stabilized the network.

1. 2D Crystal Engineering: a Four-Component Architecture at a Liquid-Solid Interface Jinne Adisoejoso 1 , Kazukuni Tahara², Satoshi Okuhata², Shengbin Lei 1 , Yoshito Tobe², Steven De Feyter 1 1 Afdeling Moleculaire en Nanomaterialen, Departement Chemie, Katholieke Universiteit Leuven, B-3001, Heverlee, Belgium ² Division of Frontier Materials Science, Graduate school of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan J. Adisoejoso, K. Tahara, S. Okuhata, S. Lei, Y. Tobe, S. De Feyter, Angew. Chem. Int. Ed. 2009 , 48 A four-component 2D crystal has been formed at a liquid-solid interface and successfully visualized by scanning tunneling microscopy. Simply premixing the four components and applying the solution onto the graphite surface leads to the spontaneous self-assembly of the 2D crystal. Furthermore, the presence of the selected guest molecules induces a structural transformation of the host network from a non-porous to a porous network by co-adsorption inside the formed pores. Building Blocks We have demonstrated the successful 2D crystal engineering of a complex 4-component network at the liquid-solid interface as revealed by scanning tunneling microscopy. After optimizing the ratio, simply mixing the four different components and bringing the solution in contact with the graphite substrate leads to a spontaneous formation of the 2D 4-component crystal. Both hydrogen bonding and van der Waals interactions stabilize the network. Furthermore, we identified the conditions to induce the structural transformation of an initial non-porous network to a porous one (at the level of the bisDBA-C 12 molecules), by co-adsorbing the appropriate template molecules which fill and stabilize the pores. Unraveling the concepts of 2D crystal engineering opens the way to the formation of more complex and functional surface nanopatterns and might find applications in several fields. Introduction Experimental Conclusions Other Combinations Key to Stabilization I x z y HOPG solution monolayer tip I = Tunneling current (10 -10 to 10 -9 Å) V = Voltage Φ = Effective tunneling barrier (effective barrier height) s = Spacing (typically few 10 -10 m) Scanning Tunneling Microscopy Structural Transformation Four Components Acknowledgement This work is supported by K.U.Leuven through GOA 2006/2, the Institute of Promotion of Innovation by Science and Technology in Flanders (I.W.T.), the Fund of Scientific Research – Flanders (FWO), the Belgian Federal Science Policy Office through IAP-6/27, and a Grant-in-aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan. bisDBA-C 12 forms a linear packing at the 1-octanoic acid – HOPG interface Upon premixing with COR and ISA, a structural transformation is observed Both voids of the Kagomé network can be filled up, simply by premixing the components COR + TRI or TRI itself also induce structural transformation ISA: unsuccesful COR: unsuccesful COR + ISA: succesful COR + ISA + TRI: succesful COR + TRI: succesful TRI: succesful