Modulation of interfacial electronic coupling between (porphinato)metal complexes and gold nanoparticles via carbodithioate and thiol linkers

COLL 407

Tae-Hong Park, parkth@sas.upenn.edu and Michael J. Therien, therien@sas.upenn.edu. Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104-6323
[5-((4'-X-phenyl)ethynyl)porphinato]zinc(II)-functionalized gold nanoparticles (AuNPs) 1-Au (X = CS2–) and 2-Au (X = S) have been synthesized via ligand exchange reactions utilizing dodecylamine-protected AuNP precursors. Electronic absorption and emission spectroscopic data show that 1-Au displays unique signatures not associated with 2-Au, indicating that the carbodithiote linkage provides augmented electronic coupling between the AuNP and the (porphinato)metal chromophore relative to that afforded by classic thiol surface modification. Consistent with these results, resonance Raman spectroscopy of 1-Au reveals mode enhancements congruent with [(phenylethynyl)porphinato]zinc(II)-(Au surface) charge resonance, that are absent in analogous 2-Au spectra. These data, coupled with the facts that carbodithioate-terminated aryleneethynylene compound synthesis is facile, and subsequent Au surface functionalization straightforward, suggest considerable potential for monocarbodithioate- and α,ω-bis(carbodithioate)-functionalized conjugated species in fundamental nanoscience.