Magnetic phase transition in valence tautomers as polymorphs of 3-iodolawsone: Single crystal X-ray structure, DSC and EPR studies

TitleMagnetic phase transition in valence tautomers as polymorphs of 3-iodolawsone: Single crystal X-ray structure, DSC and EPR studies
Publication TypeJournal Article
Year of Publication2009
AuthorsZaware, SB, Dagade-Waghmode, S, Gonnade, RG, Srinivas, D, Rane, SY
JournalJournal of Molecular Structure
Volume938
Issue1-3
Pagination328-335
Date PublishedDEC
ISSN0022-2860
Keywords3-Iodolawsone, Hydroxynaphthoquinone (HNQ), Hydroxynaphthosemiquinone radical (HNSQ), Magnetic phase transition, Polymorphs, Valence tautomers
Abstract

Three polymorphs of 3-iodolawsone (I-III) have been isolated and characterized by single crystal X-ray diffraction, electron paramagnetic resonance (EPR) spectroscopy and differential scanning calorimetry (DSC) techniques. Polymorphs I and II were crystallized from methanol in two different valence tautomeric forms: hydroxynaphthoquinone (HNQ) and hydroxynaphthoseimquinone (HNSQ) as needles and thick plates, respectively. Polymorph III was crystallized from ethanol in HNQ form, as thin plates Chiral crystals of I belongs to the orthorhombic P2(1)2(1)2(1) space group: II and III belong to the monochnic non-centrosymmetric space group Cc. The molecules are packed via O-H O bonding and pi . pi stacking interactions. The study reveals that relatively stronger intermolecular H-bonding (2.02 angstrom) and most favoured pi . pi stacking (similar to 3 49 angstrom) interactions lead II to HNSQ radicals, presence of which was confirmed by EPR (g = 2.0052) spectroscopy. Interestingly, these materials exhibit crystal-to-crystal magnetic phase transition from polymorph I (diamagnetic) to polymorph II (paramagnetic structure) at 171.1 degrees C as identified by DSC and X-ray crystallographic studies (C) 2009 Elsevier B.V. All rights reserved

DOI10.1016/j.molstruc.2009.10.005
Type of Journal (Indian or Foreign)Foreign
Impact Factor (IF)1.599
Divison category: 
Catalysis and Inorganic Chemistry
Center for Material Characterization (CMC)