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Mechanism for tautomerization induced conductance switching of naphthalocyanin molecule
KTH, School of Biotechnology (BIO), Theoretical Chemistry.
KTH, School of Biotechnology (BIO), Theoretical Chemistry.ORCID iD: 0000-0003-0007-0394
2009 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 95, no 18Article in journal (Refereed) Published
Abstract [en]

Reaction mechanism for tautomerization process of a single naphthalocyanin molecule has been studied using density functional theory. It is found that tautomerization of the naphthalocyanin molecule is not a concerted reaction, but a step-wise process in that one hydrogen atom transfers after another. A stable intermediate state and the possible transition state of the reaction processes have been located. The occurrence of the intermediate state suggests that the tautomerization induced conductance switching involves four conductance states with different conductances, and the earlier proposed two-state system model is not valid.

Place, publisher, year, edition, pages
2009. Vol. 95, no 18
Keyword [en]
density functional theory, isomerisation, organic compounds, scanning tunneling microscope, total-energy calculations, wave, basis-set, conformational-changes, single molecules, atom-transfer
URN: urn:nbn:se:kth:diva-18948DOI: 10.1063/1.3224186ISI: 000271666800036ScopusID: 2-s2.0-71049191107OAI: diva2:336995
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-05-24Bibliographically approved
In thesis
1. Understanding the Structure and Reaction of Single Molecules on Metal surfaces from First Principles
Open this publication in new window or tab >>Understanding the Structure and Reaction of Single Molecules on Metal surfaces from First Principles
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of surface adsorption and reaction is not only interesting from a scientific point of view, but also important in many application fields such as energy, environment, catalysis, corrosion, electronic device, and sensor. Theoretical calculations are essential in these studies.

In this thesis, first principles studies for the structure and reaction of some important single molecules on the surface are presented. Dehydrogenation of single trans-2-butene molecule on a Pd(110) surface is the first example. The adsorption configurations of both reactant and produce are assigned and the whole dehydrogenation pathway is revealed. Our calculations show that the reactant, i.e. trans-2-butene molecule, undergoes a rotation before dehydrogenation occurs, which is an important detail that cannot be observed directly in scanning tunneling microscopy (STM) experiments. The dissociation and rotation processes of single oxygen molecule on a Pt(111) surface have been a subject of extensive studies in the past. A new intermediate state with a peculiar configuration is identified. The puzzled adsorption site is well explained. The calculated energy barriers agree well with experimental results for both dissociation and rotation processes.

Another aspect addressed in this thesis is the mechanism of molecular electronic switches induced by molecular structural changes. By carefully examining the tautomerization process of a naphthalocyanine molecule, an intermediate state is located on the potential surface of the tautomerization. Our calculations indicate that the experimentally observed switching involves four-states, rather than the two-state as proposed by the experimentalists. In a joint experimental and theoretical study the dehydrogenation, tautomerization, and mechanical switching processes of a single melamine molecule on a Cu(100) surface have been comprehensively examined. A new dual-functional molecular device with integrated rectifying and switching functions is made for the first time. In collaborating with another experimental group, we have simulated the switching process of a single 1,1,2,3,4,5-hexaphenylsilole molecule on a Cu(111) surface. The role of the orientation of the molecule is carefully examined and a new switching mechanism is proposed.

Switching processes are strongly associated with the inelastic electron tunneling. We have proposed a statistical model that allows explaining the non-integer exponent in the power-law relationship between the switching rate and tunneling current. In this model, the importance of the randomness in inelastic electron excitations and the lifetime of the immediate state are emphasized. It has shown that the inelastic electron tunneling is a collection of various n-electron processes with different statistical weight.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xii, 72 p.
Trita-BIO-Report, ISSN 1654-2312 ; 2011:16
National Category
Theoretical Chemistry
urn:nbn:se:kth:diva-33565 (URN)978-91-7415-978-3 (ISBN)
Public defence
2011-06-10, FA32, AlbaNova University Center, Roslagstullsbacken 21, Stockholm, 10:00 (English)
QC 20110524Available from: 2011-05-24 Created: 2011-05-10 Last updated: 2011-05-24Bibliographically approved

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