Polymorphism in chloro derivatives of 1,4-naphthoquinone: Experiment and density functional theoretic investigations

Molecular interactions underlying polymorphs of chlorine containing 1,4-naphthoquinone derivatives have been investigated by employing single crystal X-ray, H-1 NMR, FTIR and electronic spectra experiments combined with density functional theory. Two polymorphs of 2,3-dichloro-1,4-naphthoquinone possessing (i) triclinic space group P-1(A1 and A3), and (ii) orthorhombic with Pb2(1a) (A2) space group were obtained. The polymorph A3 has two molecules in its asymmetric unit which facilitate C-H center dot center dot center dot O interactions engendeing polymeric planar sheets. The two polymorphs of 2-amino-3-chloro-1,4-naphthoquinone reveal monoclinic forms with Pc (B1) and C-2/C (B2) space groups. A tetramer of B2 molecule possess N-H center dot center dot center dot O interactions. The polymorphs of 2-chloro-3-hydroxy-1,4-naphthoquinone crystallizes in monoclinic space groups Pc (C1) and Pn (C2). Polymeric chain of C2 molecules results via O-H center dot center dot center dot O interactions and the chains further are connected through C-H center dot center dot center dot Cl and pi-pi stacking interactions those arise from benzenoid and quinonoid centroid. Moreover A3 facilitates the dimer via the halogen bonding interactions. Furthermore hydrogen bonding renders stability to the dimer C2. On the other hand compound B2 does not favor dimer formation. These inferences based on experimental observations are rationalized through the use of the dispersion corrected M06-2x functional based density functional theory. Further time dependent density functional theory has been used to assign the electronic transitions in UV-visible spectra of A3, B2 and C2. (C) 2016 Elsevier B.V. All rights reserved.