3P139
NLO 分子スイッチの超分極率増大に関する Through-Space/Bond
軌道間相互作用解析（九大院・総理工 1，JST-CREST2）○Jiang Lizhi1，折本 裕一 1，青木 百合子 1, 2

Through-space/bond interaction analysis on NLO properties
enhancement of molecular switches(Kyushu Univ.1 ，JST-CREST2) ○Jiang Lizhi1，Yuuichi Orimoto1，Yuriko Aoki1, 2

Recently, the nonlinear optical materials with controlled switching properties draw a lotof interests, because such kinds of materials are good candidates for optical information
storage devices, and photoresponsive materials, as well as biosensors. A good NLO switch
should exhibit an enough large difference of the response between the two states. To date, avariety of the NLO switches have been designed and investigated experimentally andtheoretically [1-2]. There are several kinds of the molecular switches, of which, thetransformation can be caused by the acidochromes or photochromes, and so on. In this work,
we focus on the acidochromic induced tunable NLO switches, closed form (CF) and open
form (OF) of (10-ethenyl-indolino[2,1-b]oxazolidines), as shown in Fig. 1. When the pHs ofthe environments change, the structures of the acidochromic compounds are tuned. The
transformation of the structures can be detected by comparing the absorption spectra.
Although the designs and investigations of the mechanisms are increasing, the further deep
investigations of the mechanism are still on the way.

Fig. 1 The switching procedures of target molecules (10-ethenyl-indolino[2,1-b]oxazolidines).
This mechanism of the switchable properties can be examined through orbital interactionperspective. The concept of through space/bond (TS/TB) orbital interaction which wasoriginally proposed by R. Hoffmann, et al.[3], is very useful in demonstrating the mechanismof the stereoelectronic effects and charge transfer. Our group developed the TS/TB orbital
interaction analysis in ab initio level[4], in this analysis, the interactions between orbitals areestimated quantitatively. The procedure of theTS/TB orbital interaction analysis in ab initio
level is by modifying the exponent α of theGaussian-type orbitals (exp(-αr2)) in the basis-sets.
In the procedure, the estimation of the interaction
between hydrogen-like atoms A and B wasconsidered as an example (Fig. 2(a)). AOs r and sbelong to atoms A and B, respectively. The
absolute magnitude of the exponents in theGaussian-type functions related to the interaction
between r and s should be increased gradually until
orbital overlap is completely eliminated. And theFig. 2 The procedure of TS/TB orbitaldeletion.

π-π interaction is deleted as shown in Fig. 2(b). The finite-field(FF) method has been applied
for the (hyper)polarizabilities calculations. All the molecules are optimized at HF/6-31G(d),and the polarizability and first hyperpolarizabilities are also calculated at HF/6-31G(d) inGAUSSIAN 09.
For the OF system as shown in Fig. 3, the first hyperpolarizability β is 6300.49 au. The βof the CF is 712.99 au. The ratio of the β between OF and CF is 8.84 (OF/CF). The big ratiosof the hyperpolarizabilities between CF and OF suggest that these kinds of molecules will bea good candidate for the molecular switches.
There are two assumptions of theeffects that cause the big difference ofthe hyperpolarizabilities between CFand OF. One of the factors causing thelarge hyperpolarizability of OF may befrom the electron transfer (seeFig.3(a)) , another one may be comefrom the interaction between the cation
and anion formed after the ring is open
Fig. 3 (a) The electron transfer along the backbone(see Fig.3(b)).
of OF, (b) electron interaction between the anion
The mechanism of the enhancement
and cation in the OF.
of the hyperpolarizabilities of OF
molecules is analyzed by evaluating the TS/TB orbital interactions. The investigations are stillon the way.
[1] Nenon, S.; Champagne, B. J. Chem. Phys. 2013, 138, 204107.
[2] Sanguinet, L.; Pozzo, J. L.; Rodriguez, V.; Adamietz, F.; Castet, F.; Ducasse, L.; Champagne, B. J. Phys.
Chem. B 2005, 109, 11139.
[3] Hoffmann, R.; Imamura, A.; Hehre, W. J. J. Am. Chem. Soc. 1968, 90, 1499.
[4] Orimoto, Y.; Aoki, Y. Int. J. Quantum Chem. 2003, 92, 355.