C-C bond unsaturation degree in monosubstituted ferrocenes for molecular electronics investigated by a combined near-edge x-ray absorption fine structure, x-ray photoemission spectroscopy, and density functional theory approach

Journal Article · Sat Apr 07 00:00:00 EDT 2012 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.3698283· OSTI ID:22047191

Boccia, A; Lanzilotto, V; Marrani, A G; Zanoni, R ^[1]; Stranges, S ^[1]; Alagia, M ^[2]; Fronzoni, G; Decleva, P ^[3]

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1. Dipartimento di Chimica, Universita degli Studi di Roma ''La Sapienza'', piazzale Aldo Moro 5, I-00185 Rome (Italy)
2. IOM-CNR, Laboratorio TASC, I-34149 Basovizza, Trieste (Italy)
3. Dipartimento di Scienze Chimiche, Universita di Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy and IOM-CNR Democritos, Trieste (Italy)

We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the {sigma}/{pi} hyperconjugation in EtFC and the {pi}-conjugation in VFC and EFC.

• OSTI ID: 22047191
• Journal Information: Journal of Chemical Physics, Vol. 136, Issue 13; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
ABSORPTION
ABSORPTION SPECTROSCOPY
CARBON
CHEMICAL BONDS
CHEMICAL SHIFT
DENSITY FUNCTIONAL METHOD
ELECTRONIC STRUCTURE
FERROCENE
FINE STRUCTURE
MOLECULAR STRUCTURE
PHOTOEMISSION
PHOTON-MOLECULE COLLISIONS
SYNCHROTRON RADIATION
X RADIATION
X-RAY PHOTOELECTRON SPECTROSCOPY
X-RAY SPECTROSCOPY