Structures of four bis(pyridine-2-yl) ketone arylhydrazone derivatives: differences in molecular conformations and intermolecula interactions

摘要

Crystal structures of bis(pyridine-2-yl) ketone arylhydrazone derivatives, [6, (Py)_2C=NNHC_6H_4X (X = H, 2-O_2N, 4-O_2N and 4-I] have been determined from data collected at 120 K. A third polymorph of (6: X = 4-O_2N) has been characterized. Compounds, (6: X = 2-O_2N) and two of the three now known polymorphs of (6: X = 4O_2N), β- [Bakir and Brown, J. Mol. Struct. 641 (2002) 183-191] and γ [this study], have similar conformations, which are quite distinct from that of α-(6: X = 4-O_2N) [Bakir et al, Acta Crystallogra. C61 (2005) o607-o609] and (6: X = 4-I) [ this study]. The molecular conformation of (6: X = H) is intermediate between the two extremes. For compound ( 6: X = H), the supramolecular arrangement is made from C-H···N hydrogen bond, π···π stacking and C-H-(arene) interactions, while that for (6: X = 4-I) is composed of N-H···N, C-H···N and C-H-n interactions. CHO and π···stacking interactions are present in γ-(6: X = 4-O_2N). In contrast, (6: X = 2-O_2N) exists as discrete molecules with no intermolecular contacts within the appropriate sum of van der Waals radii.