期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 115, 期 12, 页码 2896-2901出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1718965115
关键词
chirality; mechanoresponsive crystals; topochemical reactions; twisting; spontaneous
资金
- Department of Science and Technology Ramanujan Fellowship
- Department of Science and Technology Swarnajayanti Fellowship
- University Grant Commission Fellowship
Crystals that show mechanical response against various stimuli are of great interest. These stimuli induce polymorphic transitions, isomerizations, or chemical reactions in the crystal and the strain generated between the daughter and parent domains is transcribed into mechanical response. We observed that the crystals of modified dipeptide LL (N-3-L-Ala-L-Val-NHCH2C CH) undergo spontaneous twisting to form right-handed twisted crystals not only at room temperature but also at 0 degrees C over time. Using various spectroscopic techniques, we have established that the twisting is due to the spontaneous topochemical azide-alkyne cycloaddition (TAAC) reaction at room temperature or lower temperatures. The rate of twisting can be increased by heating, exploiting the faster kinetics of the TAAC reaction at higher temperatures. To address the role of molecular chirality in the direction of twisting the enantiomer of dipeptide LL, N-3-D-Ala-D-Val-NHCH2C CH (DD), was synthesized and topochemical reactivity and mechanoresponse of its crystals were studied. We have found that dipeptide DD not only underwent TAAC reaction, giving 1,4-triazole-linked pseudopolypeptides of D-amino acids, but also underwent twisting with opposite handedness (left-handed twisting), establishing the role of molecular chirality in controlling the direction of mechanoresponse. This paper reports (i) a mechanical response due to a thermal reaction and (ii) a spontaneous mechanical response in crystals and (iii) explains the role of molecular chirality in the handedness of the macroscopic mechanical response.
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