Communication pubs.acs.org/crystal
Uniaxial Negative Thermal Expansion in an Organic Complex Caused by Sliding of Layers† Suman Bhattacharya and Binoy K. Saha* Department of Chemistry, Pondicherry University, Pondicherry, India 605014 S Supporting Information *
ABSTRACT: Generally, materials undergo thermal expansion along all directions upon heating. The very few materials that show the opposite trend along one or more of their crystallographic axes have plenty of applications. Herein we report a negative thermal expansion along one axis in the crystal structure of a 1:1:1 organic complex of 1,3,5-benzenetricarboxylic acid (BTA), 2,6-dimethylaniline (DMA), and water molecules. The unusual thermal expansion in this structure is caused by sliding of layers, which is unprecedented. represented by the linear thermal expansion coefficient, αl = (lT − l0)/l0(T − T0) with respect to the three crystallographic axes, and the values lie generally 2σ(I) and wR2 = 0.1221 for all 13564 data. S = 1.009. At 165 K: a = 8.3768(13), b = 13.7290(10), c = 14.5547(10), α = 90.157(6), β = 102.521(9), γ = 95.439(9), R1 = 0.0556 for 7459 reflections with I > 2σ(I) and wR2 = 0.1619 for all 13511 data. S = 1.051. At 210 K: a = 8.4027(12), b = 13.7129(10), c = 14.6157(8), α = 90.126(5), β = 102.668(8), γ = 95.329(9), R1 = 0.0534 for 7465 reflections with I > 2σ(I) and wR2 = 0.1479 for all 13391 data. S = 1.020. At 255 K: a = 8.4236(5), b = 13.6964(8), c = 14.6918(7), α = 90.012(4), β = 102.972(4), γ = 95.368(5), R1 = 0.0606 for 7532 reflections with I > 2σ(I) and wR2 = 0.1751 for all 13341 data. S = 1.020. At 300 K: a = 8.4373(3), b = 13.6980(5), c = 14.7629(6), α = 89.956(3), β = 103.262(3), γ = 95.312(3), R1 0.0551 for 7709 reflections with I > 2σ(I) and wR2 = 0.1525 for all 18052 data. S = 1.030. (16) Senthil Kumar, V. S.; Nangia, A.; Kirchner, M. T.; Boese, R. New J. Chem. 2003, 27, 224−226. (17) arXiv.org: 1204.3007v1.
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dx.doi.org/10.1021/cg300980s | Cryst. Growth Des. 2012, 12, 4716−4719
