Shear stress effect on molecular crystals and development of their new synthetic methods

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The shear stress effect has been studied in order to introduce it to materials science for organic materials and molecular crystals. We have used the sapphire anvil cell to generate shear stress by the rotation of the lower anvil under pressure and performed the in situ observations under a microscope with spectroscopic measurements.1.Preparation of TMPD-TCNQ charge-transfer saltWe have attempted the syntheses by shear deformation. On applying the shear stress on TMPD N,N,N',N'-tetramethyl-p-phenylenediamine, colorless) and TCNQ (orange) films, the color at the outer part on the culet changed to blue-black. From the Raman spectra, the formation of TMPD-TCNQ CT salt at the blue-black part was confirmed.2.Shear stress effect on Pt(dpg)_2, bis(diphenylglyoximato) platinum(II)Pt(dpg)_2 is sensitive to the stress ; its color changes from red to green to yellow. We have studied the shear stress effect by Raman spectroscopy. The C=N bands at 1431 and 1452 cm^<-1> were shifted significantly by the shear deformation. The estimation of the effect was performed by their shifts in wavenumber. On applying the shear stress by the rotation of 10゜, the stress was increased from 0.14 GPa to 0.18 GPa at the center part and from 1.77 GPa to 2.41 GPa at the outer part. It was noted that the shear stress was applied more strongly at the outer part.3.Shear stress effect on Spiropyran 6-nitro-BIPSThe color of 6-nitro-BIPS at the outer part was changed from orange to green under shear deformation. As being released from the stress, it changed from green to purple. Because of strong fluorescence, the rotation-vibration Raman spectrum could not be obtained at the green part, while the spectra were measured at the orange and purple parts. This result suggests that 6-nitro-BIPS molecule under shear stress is different from one at ambient pressure.