STRUCTURE OF THE ERGOLINE DERIVATIVE 1,1-DIETHYL-3-[(2R,3R,5R,8S,10S)-2,3-DIHYDRO-2,6-DIMETHYL-8-ERGOLINYL]UREA AT 3 DIFFERENT TEMPERATURES (295-K, 50-K AND 15-K)

The structure of the ergoline derivative 1,1-Diethyl-3-[(2R,3R,5R,8S,10S)-2,3-dihydro-2,6-dimethyl-8-ergolinyl]-urea has been determined by X-ray single crystal diffraction at three temperatures: 295, 50 and 15 K. Large displacement parameters of the diethyl-urea side group atoms cause rather improper bond distances at room temperature which, after cooling, adopt normal values. An inspection of the displacement parameters expressed in U(eq)'s, shows that even the temperature reduction from 50 to 15 K causes an average decrease of U(eq)'s by 33%. At room temperature, the individual displacement parameters depend strongly on the atomic distances from the molecular center of gravity. This dependence disappears almost completely at 15 K.