Journal of Applied Crystallography

Volume 36, Part 1 (February 2003)

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J. Appl. Cryst. (2003). 36, 141-145    [ doi:10.1107/S0021889802021878 ]

Reversible displacive phase transition in [Ni(en)3]2+(NO3-)2: a potential temperature calibrant for area-detector diffractometers

L. J. Farrugia, P. Macchi and A. Sironi

Abstract: The coordination complex [Ni(en)3]2+(NO{}_{3}^{- })2 (en = 1,2-diaminoethane) undergoes a sharp reversible displacive phase transition at ~109 K, changing space group from P6322 above the transition temperature to P6522 below. The phase change is accompanied by a tripling of the c axis on cooling, resulting in an easy detection of the transition in images from area-detector diffractometers. The transition has been followed using a Nonius KappaCCD and a Bruker SMART APEX CCD. Data sets were collected over the temperature range 100-113 K and integrated using the low-temperature orientation matrix. Reflections with l [not equal to] 3n show a smooth and rapid decrease in intensity to zero on warming from 106.5 to 111 K. The results are reproducible to within ±2 K in two laboratories and suggest that this compound may be useful as a liquid-nitrogen cryo-calibrant for diffraction instruments equipped with area detectors.

Keywords: phase transition; temperature calibrant; area detectors.

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