305830-98-2Relevant academic research and scientific papers
Investigation of tightly coupled porphyrin arrays comprised of identical monomers for multibit information storage
Clausen,Gryko,Yasseri,Diers,Bocian,Kuhr,Lindsey
, p. 7371 - 7378 (2007/10/03)
Our prior designs for molecular-based information storage devices have employed multiple redoxactive units organized in weakly coupled, covalently linked arrays. To explore a simpler design, we report here the synthesis of porphyrin arrays where porphyrins with identical oxidation potentials are directly linked to one another instead of joined via a molecular linker. Oxidative coupling with AgPF6 of zinc(II)-5,15-bis(4-tert-butylphenyl)-10-phenylporphyrin, obtained by a rational synthesis, afforded the expected dimer joined by a meso-meso linkage and an unexpected trimer joined by meso-meso linkages. For attachment to an electroactive surface we synthesized a meso-linked porphyrin dimer with a thiol-linker in one of the meso positions. The S-acetyl protecting group was used to avoid handling free thiol groups. Coupling of zinc(II)-5,10,15-tris(3,5-di-tertbutylphenyl)porphyrin ('upper half') and zinc(II)-5-[4-(S-acetylthio)phenyl]-10,20-bis(3,5-di-tertbutylphenyl)porphyri n ('lower half') afforded three different meso-linked dimers with the desired dimer as the main product. Electrochemical examination of the meso-linked dimer in solution shows that the first two oxidation potentials of the array differ by ~0.15 V and straddle the value exhibited by the monomeric constituents. The third and fourth oxidation potentials of the array are also split although to a lesser extent (~0.08 V) than the first and second. For the meso-linked trimer, the first three oxidation waves are also split; however, these waves are severely overlapped. The electrochemical behavior of the dimers and trimer is indicative of strong electronic interactions among the porphyrins. The thiol-derivatized meso-linked dimers form self-assembled monolayers (SAMs) on gold via in situ cleavage of the S-acetylthio protecting group. The porphyrin SAM exhibits four well-resolved oxidation waves. Regardless, the meso-meso linkage is relatively unstable upon formation of the π-cation radical(s). This characteristic indicates that the structural motif is of limited utility for molecular information storage elements.
