Switching from positive to negative thermal expansion in a tetrayne-diol compound.

Switching from positive (PTE) to negative thermal expansion (NTE) in a molecular crystal is a rare phenomenon. Here we report the switching of PTE to NTE in 1,1′-(octa-1,3,5,7-tetrayne-1,8-diyl)dicyclopentanol (1) along the crystallographic a-axis. Small PTE has been observed from 100 K to 200 K due to zigzag packing arrangement and then the large transverse vibration overpowers the PTE resulting in NTE after 200 K. [ABSTRACT FROM AUTHOR]