2016 Fiscal Year Research-status Report
Investigation of tautomerization in meso-dibenzoporphycene by intramolecular resolution atomic force microscopy and scanning tunnelling microscopy
| Project/Area Number |
16K05674
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
Custance Oscar 国立研究開発法人物質・材料研究機構, 先端材料解析研究拠点, グループリーダー (00444555)
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | 走査プローブ顕微鏡 |
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| Outline of Annual Research Achievements |
Tautomerization (intramolecular hydrogen atom transfer) is an important process in organic chemistry and biology. By using atomic and intra-molecular resolution scanning probe microscopy, we are studying the tautomerization process in meso-dibenzoporphycene ―a molecule with potential for use in photodynamic therapy and as a molecular switch. Our main goals are to clarify the influence of the local environment (surface, presence of nearby atoms and molecules) in the tautomerization process, and to characterize the subtle charge differences expected for the cis and trans forms of the molecule by intra-molecular resolution Kelvin probe force microscopy.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
We have studied the adsorption of meso-dibenzoporphycene (mDBPc) on several metallic surfaces to identify the best template to study the tautomerization reaction of this molecule. We have performed this characterization by using a combined AFM/STM implementation operated in ultra-high vacuum and at 4.8 K temperature. We have deposited the mDBPc molecules on the Ag(111), Pb(111), Cu(111) and Cu(100) surfaces. In contrast to the cases reported for phthalocyanine (Liljeroth et al., Science 31, 2007, 1203) and porphycene molecules (Kumagai et al. Nature Chemistry 6, 2014, 41) ―where cis and trans forms of the molecules were found after deposition on a metallic substrate― we have not observed a clear difference between the cis and trans forms of the mDBPc molecule upon adsorption on the metallic substrates mentioned above. This fact has made us suspect that the molecule was loosing the hydrogen atoms that produce rise to the tautomeraization reaction upon sublimation of the molecules from the evaporation cell, because the temperature for the molecular sublimation and the molecular decomposition are very close.
To verify this hypothesis, we asked a collaborator of us ―who is an expert on first-principles calculations― to make simulations of the adsorption geometry of mDBPc molecules. Our collaborators found that the differences between the AFM images of cis and trans forms of the mDBPc molecule are very subtle, almost imperceptible. However, they found that the major differences between cis and trans forms of the mDBPc molecule are in the electrostatic potential.
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| Strategy for Future Research Activity |
We will study the mDBPc molecules on the Cu(100) substrate with islands of NaCl thin-film grown on top of it. We will check whether an insulating substrate electronically decoupling the molecule from the metallic surface enables us to discern between the cis and trans forms of the mDBPc molecule.
We will spend time trying to clarify the structure of the mDBPc molecule with intramolecular resolution AFM, aiming at identifying the position and bonding state of the hydrogen atoms inside the molecule. Using atom and molecular manipulation techniques, it is possible to pick up a CO molecule from the NaCl islands, and adsorb it at the apex of the probe. This functionalization of the AFM probe with a CO molecule will enable us to obtain intra-molecular resolution AFM images.
Furthermore, in view of the predictions made by our colleagues we will try to perform Kelvin probe force microscopy (KPFM) imaging to try to differentiate between trans and cis forms of the mDBPc molecule.
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| Causes of Carryover |
Once we realized that we could not differentiate between cis and trans forms of the mDBPc molecule with our measurements, we ceased the experiments. As a consequence, a portion of originally planned budget was not used. We will transfer this amount of budget to the FY 2017.
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| Expenditure Plan for Carryover Budget |
We will use the budget transferred from the previous fiscal year, together with the budget granted for FY 2017, to perform the experiments on the mDBPc molecules mentioned above, and to attend several conferences on scanning probe microscopy to be held during FY 2017.
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Research Products
(2 results)
