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An investigation of the structural and electronic properties of covalently bonded molecular networks on metal surfaces formed through debromination reactions.
Doyle, Catherine
This thesis discusses the deposition, self-assembly, network formation, and molecule-substrate interaction of brominated molecules with four-, three- and two-fold symmetry on the Au(111), Au(110), Ag(111) and Cu(111) metal surfaces. Characterisation was carried out using scanning tunneling microscopy(STM), x-ray photoelectron spectroscopy (XPS), low energy electron diffraction(LEED), and synchrotron radiation based photoelectron spectroscopy (PES) and x-ray absorption spectroscopy (XAS). Covalently bonded nano-networks were formed via radical addition following thermal debromination of the molecules. Networks on the order of 10,000 square nanometres were observed on Au(111), and exhibited thermal stability up to 500 degrees C. Network formation was inhibited on Cu(111) by the significant molecule-substrate interaction, leading to mass transport of Cu atoms and the formation of Cu adatom islands on annealing at 350 degrees C and higher. The Ag and Cu surfaces were sufficiently reactive to catalytically cleave the C-Br bond on deposition, leading to the formation of metal-coordinated protopolymer networks. These structures were converted to covalently bonded networks after subsequent thermal annealing. The first reported in situ metalation of a free base porphyrin molecule using substrate atoms was carried out for 5,10,15,20-tetrakis(4-bromophenyl) porphyrin (H2TBrPP) on Cu(111). This also constituted the first direct observation of the reaction intermediate state on a surface. A Ni-Cu ion exchange was observed for Ni(II) 5,10,15,20-tetrakis(4-bromophenyl) porphyrin (NiTBrPP) and Ni(II) 5,15-dibromo-10,20-diphenyl porphyrin (NiDBrDPP) on Cu(111), whereby the Ni(II) ions in the porphyrin macrocycle exchanged with Cu atoms from the substrate, resulting in Cu-metalated porphyrins and metallic Ni atoms. The reaction enthalpy was the same for both NiDBrDPP/Cu(111) and NiTBrPP/Cu(111); however the entropy was greater for NiDBrDPP/Cu(111) than for NiTBrPP/Cu(111). This is attributed to the difference in symmetry of the molecules.
Keyword(s): Physics; Nanotechnology; Chemistry; Porphyrins; Scanning Tunnelling Microscopy; STM; X-ray Photoemission Spectroscopy; XPS; Synchrotron radiation; Surface science, Surface reactions, Covalent bonding, Nano-networks
Publication Date:
2013
Type: Other
Peer-Reviewed: Unknown
Language(s): English
Contributor(s): Cafolla, Attilio A.
Institution: Dublin City University
Citation(s): Doyle, Catherine (2013) An investigation of the structural and electronic properties of covalently bonded molecular networks on metal surfaces formed through debromination reactions. PhD thesis, Dublin City University.
Publisher(s): Dublin City University. School of Physical Sciences; Dublin City University. National Centre for Sensor Research (NCSR)
File Format(s): application/pdf
Related Link(s): http://doras.dcu.ie/19363/1/Catherine_Doyle_DCU_thesis.pdf
First Indexed: 2013-12-06 05:06:25 Last Updated: 2019-02-09 06:28:28