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ARS Home » Plains Area » Manhattan, Kansas » Center for Grain and Animal Health Research » Grain Quality and Structure Research » Research » Publications at this Location » Publication #374763

Research Project: Measurement and Improvement of Hard Winter Wheat End-Use Quality Traits

Location: Grain Quality and Structure Research

Title: Phase transformation induced mechanocromism in a platinum salt: a tale of two polymorphs

item Norton, Amie
item ABDOLMALEKI, MAHMOOD - University Of Texas Rio Grande Valley
item LIANG, JIAMIN - University Of Cincinnati
item SHARMA, MALVIKA - University Of Cincinnati
item GOLSBY, ROBERT - University Of Cincinnati
item ZOLLER, ANN - University Of Cincinnati
item KRAUSE, JEANETTE - University Of Cincinnati
item CONNICK, WILLIAM - University Of Cincinnati
item CHATTERJEE, SAYANDEV - Pacific Northwest National Laboratory

Submitted to: Journal of the Chemical Society Chemical Communications
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2020
Publication Date: 7/21/2020
Citation: Norton, A.E., Abdolmaleki, M.K., Liang, J., Sharma, M., Golsby, R., Zoller, A., Krause, J., Connick, W., Chatterjee, S. 2020. Phase transformation induced mechanocromism in a platinum salt: a tale of two polymorphs. Journal of the Chemical Society Chemical Communications.

Interpretive Summary: Mechanochromic materials respond to mechanical stimulus by changing color under mechanical stress such as grinding and touching. There is interest in such materials as stress sensors and in security applications. Stacking platinum (Pt) complexes have shown promise as mechanochromic materials. Changes in the environment that these complexes are exposed to, such as a mechanical change, can cause changes in the Platinum complex causing a colorimetric change in the material that can be visually observed. The change in color can also be measured via UV-visible and emission spectroscopy. However, the mechanism of this rearrangement and structural changes are not well understood. Here we report the crystal structures of the Pt stacking material before and after the mechanochromic event. Red crystals of [Pt(tpy)Cl]NO3.HNO3 were grown from nitric acid and acetone were shown to respond to touch by turning yellow. The structure of both crystals (the red and yellow) were determined using X-ray crystallography. Single crystal information was obtained through emission spectroscopy as well. We mapped out the structural rearrangement that would have to occur that would result in a shift from the red structure to the yellow structure using structural mapping. This research is significant because there is a serious gap in structural information in a mecahnochromic system. The structural information attained here can help us gain insight into the mechanochromic mechanism and aid in designing mechanochromic materials with specific properties.

Technical Abstract: Red crystals of [Pt(tpy)Cl]NO3•HNO3 show mechanochromic behaviour turning yellow when pressure is applied. The electronic character and spectroscopic signature of the red and yellow polymorphs change as a result of slipping of the molecular stacking planes in the solid state. The slippage alters the Pt•••Pt intermolecular distances from a linear stacked motif with <3.5 Å separations in the red polymorph to a stacked motif of alternating short intradimer and long interdimer interactions in the yellow polymorph.