Purify it by chromatography on alumina and eluting with pentane, also by reverse phase (ODS) HPLC using MeCN as solvent. It is stable at room temperature [Kjell et al. J Am Chem Soc 108 4111 1986, Abelt et al. J Am Chem Soc 107 4148 1985]. The 1H NMR in CCl4 has 3.18 (4H), 6.17 (t J 1.5Hz, 2H), 7.60 (t J 1.5Hz 2H).