Mechanical Fixation by Porphyrin Connection: Synthesis and Transport Studies of a Bicyclic Dimer

Abstract

The bowl-shaped, 3-fold interlinked porphyrin dimer 2 was obtained in respectable yields during macrocyclization attempts. Its bicyclic structure, consisting of a macrocycle made of a pair of acetylene interlinked tetraphenylporphyrins which are additionally linked by a C−C bond interlinking two pyrrole subunits, has been confirmed spectroscopically (2D-NMR, UV/vis, HR-MALDI-ToF MS). Late-stage functionalization provided the structural analogue 1 with acetylprotected terminal thiol anchor groups enabling single molecule transport investigations in a mechanically controlled break junction experiment. The formation of single-molecule junctions was observed, displaying large variations in the observed conductance values pointing at a rich diversity in the molecular junctions.

A review of oligo(arylene ethynylene) derivatives in molecular junctions

“…227 Initial synthetic attempts to improve on this design using a porphyrinbased cyclophane afforded instead an unusual triply-linked bowlshaped system (42), which was nevertheless subjected to conductance investigations. 228 A change of approach gave a doublylinked porphyrin cyclophane (43), for which initial conductance results were recently reported. 116 These molecular designs are a logical progression based on similar mechanosensitivity observed in junctions containing π-stacked OPE dimers.…”

Porphyrins as building blocks for single-molecule devices

“…11(a) ). 59 No clear conductance plateau was observed in the molecular traces (890 of 10000 consecutive traces), which was interpreted as an indication of numerous possible configurations of molecular junctions with comparable probability instead of the desired well-defined sulfur-to-sulfur molecular junction sketched in Fig. 11(b) .…”

Mechanical conductance tunability of a porphyrin–cyclophane single-molecule junction

“… 18 Recently the successful synthesis and characterization of mechanically fixed and flexible cofacial porphyrin cyclophanes were demonstrated. 19,20 The molecular concept is sketched in Fig. 1 : Two porphyrins are expanded by a para -ethynylbenzenethiol subunit to enable their fixation at the electrode surface (blue in Fig.…”