Synthesis of Porphyrins Bearing Hydrocarbon Tethers and Facile Covalent Attachment to Si(100)

Abstract

The use of redox-active molecules as the active storage elements in memory chips requires the ability to attach the molecules to an electroactive surface in a reliable and robust manner. To explore the use of porphyrins tethered to silicon via carbosilane linkages, 17 porphyrins have been synthesized. Fourteen porphyrins bear a tether at a single meso site, and three porphyrins bear functional groups at two beta sites for possible two-point attachment. Two high-temperature processing methods (400 degrees C under inert atmosphere) have been developed for rapid (minutes), facile covalent attachment to Si platforms. The high-temperature processing conditions afford attachment either by direct deposition of a dilute solution (1 microM-1 mM) of the porphyrin sample onto the Si substrate or sublimation of a neat sample onto the Si substrate. The availability of this diverse collection of porphyrins enables an in-depth examination of the effects of the tether (length, composition, terminal functional group, number of tethers) and steric bulk of nonlinking substituents on the information-storage properties of the porphyrin monolayers obtained upon attachment to silicon. Attachment proceeds readily with a wide variety of hydrocarbon tethers, including 2-(trimethylsilyl)ethynyl, vinyl, allyl, or 3-butenyl directly appended to the porphyrin and iodo, bromomethyl, 2-(trimethylsilyl)ethynyl, ethynyl, vinyl, or allyl appended to the 4-position of a meso-phenyl ring. No attachment occurs with substituents such as phenyl, p-tolyl, mesityl, or ethyl. Collectively, the studies show that the high-temperature attachment procedure (1) has broad scope encompassing diverse functional groups, (2) tolerates a variety of arene substituents, and (3) does not afford indiscriminate attachment. The high-temperature processing conditions are ideally suited for use in fabrication of hybrid molecular/semiconductor circuitry.

Synthesis and Photophysical Characterization of Porphyrin, Chlorin and Bacteriochlorin Molecules Bearing Tethers for Surface Attachment

“…Methanol was added, yielding a precipitate, which upon filtration afforded a pale yellow solid (14.1 g, 54%). Characterization data ( 1 H NMR, 13 C NMR and FAB‐MS spectra) were consistent with those obtained from samples prepared previously (62).…”

Direct alkylation of pyrrole with vinyl substituted aromatics: versatile precursors for the synthesis of porphyrinoid macrocycles

“…Attempted reaction with valeraldehyde under the same condition resulted in extensive scrambling on the other hand. 15 In summary, we report that regioselective addition of pyrrole to vinyl substituted aromatics bearing electron-withdrawing groups. can be applied to the synthesis of various porphyrins and coremodified porphyrins.…”

“…14 Nitrovinyl-substituted pyrrole (12), thiophene (13) and furan (14) also underwent regioselective addition of pyrrole in the presence of InCl 3 in neat pyrrole solvent (Scheme 3). Superior yields were obtained when the pyrrole N-H was protected with Boc group (15). Small amount of (20) was also isolated from the reaction mixture.…”

“…As shown in Scheme 4, In(III)-catalyzed condensation of (22) with pyrrole afforded dipyrromethane (23) in 31% yield. 15 Unlike bis-vinyl benzene (1) or bis-vinyl pyridine (2), acid-catalyzed condensation of bis-vinyl pyrrole (24) resulted in the formation of (25) as sole product in 61% yield. Rapid reversible cleavage of initially formed product must be involved in this reaction.…”

Hybrid Silicon-Molecular Electronics

“…The similarity of the calculated number and fitted value indicated the validity of the linear fitting of Eq. (11).…”