Department of Chemistry and Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan.
J Am Chem Soc. 2010 Oct 13;132(40):14172-8. doi: 10.1021/ja105356w.
The photomechancial effect of a rectangular plate two-component cocrystal composed of a photochromic diarylethene derivative, 1,2-bis(2-methyl-5-(1-naphthyl)-3-thienyl)perfluorocyclopentene (1o), and perfluoronaphthalene (FN) has been examined. The crystal of 1o·FN with the size of 1-5 mm in length exhibits reversible bending motion upon alternate irradiation with ultraviolet (UV) and visible light. The reversible bending could be repeated over 250 times. In situ X-ray crystallographic analysis revealed that the deformation of the crystal is due to the elongation of the b-axis of the unit cell, which corresponds to the long axis of the plate crystal, induced by the shape change of component diarylethene molecules upon photocyclization. The bending motion was observed even at 4.7 K, and dynamic measurement of the bending proved that the anisotropic expansion of the crystal takes place in the microsecond time scale at the low temperature. Molecular crystal cantilevers made of 1o·FN can lift metal balls, the weight of which is 200-600 times heavier than the weight of the crystal, upon UV irradiation. The maximum stress generated by UV irradiation was estimated to be 44 MPa, which is 100 times larger than that of muscles (∼0.3 MPa) and comparable to that of piezoelectric crystals, such as lead zirconate titanate (PZT) (∼50 MPa).
由光致变色二芳基乙烯衍生物 1,2-双(2-甲基-5-(1-萘基)-3-噻吩基)全氟环戊烯（1o）和全氟萘（FN）组成的矩形板二组分共晶的光机械效应已被研究。长度为 1-5 毫米的 1o·FN 晶体在交替照射紫外（UV）光和可见光时表现出可逆弯曲运动。这种可逆弯曲可以重复 250 多次。原位 X 射线晶体学分析表明，晶体的变形是由于单元胞的 b 轴伸长引起的，这与组成二芳基乙烯分子在光环化时形状变化相对应，这是板状晶体长轴的伸长。即使在 4.7 K 下也观察到弯曲运动，并且弯曲的动态测量证明在低温下，晶体的各向异性膨胀发生在微秒时间尺度内。由 1o·FN 制成的分子晶体悬臂在 UV 照射下可以举起重量是晶体重量 200-600 倍的金属球。UV 照射产生的最大应力估计为 44 MPa，这是肌肉（约 0.3 MPa）的 100 倍，与压电晶体（如锆钛酸铅（PZT）（约 50 MPa）相当。
