The Different Faces of 4'-Pyrimidinyl-Functionalized 4,2':6',4'- Terpyridines: Metal-Organic Assemblies from Solution and on Au(111) and Cu(111) Surface Platforms

摘要

A comparative investigation of crystal growth from solution and on-surface assembly in vacuo between copper and three 4′-(2-R-pyrimidin-5-yl)-4,2′:6′,4′′-terpyridines, with R = H ( 1 ), Me ( 2 ), or Et ( 3 ), is presented. In solution, ligand 3 combines with copper(II) acetate or copper(I) triflate in MeOH solution to give [Cu_(2)(OAc)_(4)( 3 )]_( n ) or {[Cu( 3 )(OMe)(MeOH)][CF_(3)SO_(3)]·MeOH}_( n ). In [Cu_(2)(OAc)_(4)( 3 )]_( n ), paddle-wheel {Cu_(2)(μ-OAc)_(4)} nodes direct the assembly of one-dimensional (1D) zigzag chains which pack into two-dimensional (2D) sheets. In {[Cu( 3 )(OMe)(MeOH)][CF_(3)SO_(3)]·MeOH}_( n ), the solvent is a ligand and also generates {Cu_(2)(μ-OMe)_(2)} units which function as planar 4-connecting nodes to generate a 2D (4,4) net with ligand 3 . On Au(111) or Cu(111) surfaces in vacuo , no additional solvent or anions are involved in the assembly. The different substituents in 1 , 2 , or 3 allow precise molecular resolution imaging in scanning tunneling microscopy. On Au(111), 1 and 2 assemble into close-packed assemblies, while 3 forms a regular porous network. The deposition of Cu adatoms results in reorganization leading to ladder-shaped surface metal–organic motifs. These on-surface coordination assemblies are independent of the 4′-substituent in the 4,2′:6′,4′′-tpy and are reproduced on Cu(111) where Cu adatoms are available during the deposition and relaxation process at room temperature. Upon annealing at elevated temperatures, the original surface assemblies of 1 and 3 are modified and a transition from ladders into rhomboid structures is observed; for 2 , a further quasi-hexagonal nanoporous network is observed.