2004 Fiscal Year Final Research Report Summary
A theoretical study on the role of conical intersection in the photioisomerization of conjugated polyenes
| Project/Area Number |
15550003
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical chemistry
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| Research Institution | Akita University |
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Principal Investigator |
AMATATSU Yoshiaki Akita University, Associate Professor, 工学資源学部, 助教授 (90241653)
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| Project Period (FY) |
2003 – 2004
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| Keywords | ab initio MO calculation / π-conjugated polyenes / excited state / photoisomerization / conical intersection |
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| Research Abstract |
The photoisomerizations of π-conjugated polyenes have been of great interest in a wide variety of chemistry, physics, biology and material science. However, the reasonable pictures are still far from reality. One of the most important ingredients is the information on the conical intersection (CIX) where the relaxation takes place. In this project, we calculated CIXs as well as other important conformations by means of reliable levels of ab initio molecular orbital (MO) calculations so as to give new and reasonable pictures of photochemistry of π-conjugated polyenes. Actual molecules treated in this project are phenylacetylene (PA), diphenylacetylene (DPA) and dimethylaminobenzonitrile (DMABN). These have no reasonable pictures because of lack of S_2/S_1-CIX.
PA : S_2/S_1-CIX is characterized by two factors. That is, the benzene ring loses its aromaticity and turns to be a quinoid structure and the ethynyl part turns to be allene-like. The feature of S_2/S_1-CIX is possible to give a reasonable picture of complicated absorption spectrum.
DPA : The globally stable structure in S_1(S_1-geometry) takes a trans-bent form with C_<2h> symmetry. The S_/S_1-CIX is located in the half way from the D_<2h> structure and S_1-geometry. We gave a reasonable picture on the temporal behavior by an analysis of potential energy surfaces.
DMABN : At S_2/S_1-CIX, DMABN has a quinoid structure where the dimethylamino part is perpendicularly twisted against the remaining part. S_2/S_1-CIX is a crossing region between charge transfer and π-π^* locally excited states. We further analyzed the potential energy surfaces so as to settle down serious controversy between TICT and PICT models for the DMABN photochemistry.
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