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Crystal structures of bis(pyridine-2-yl) ketone arylhydrazone derivatives, [ 6 , (py) 2 C=NNHC 6 H 4  X  ( X  = H, 2-O 2 N, 4-O 2 N and 4-I] have been determined from data collected at 120 K. A third polymorph of ( 6 :  X  = 4-O 2 N) has been characterized. Compounds, ( 6 :  X  = 2-O 2 N) and two of the three now known polymorphs of ( 6 :  X  = 4-O 2 N),  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 2 N) [Bakir et al, Acta Crystallogra. C 61  (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-π interactions. C—HO and π···π stacking interactions are present in  γ -( 6 :  X  = 4-O 2 N). In contrast, ( 6 :  X  = 2-O 2 N) exists as discrete molecules with no intermolecular contacts within the appropriate sum of van der Waals radii.

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