02289nas a2200265   4500008004100000022001400041245013500055210006900190260007300259300001200332490000800344520125900352653001801611653003201629653004501661653003001706653001501736653002201751100002401773700002801797700002401825700002101849700002201870856013101892       2009                        eng d  a0022-286000aMagnetic phase transition in valence tautomers as polymorphs of 3-iodolawsone: Single crystal X-ray structure, DSC and EPR studies0 aMagnetic phase transition in valence tautomers as polymorphs of   aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcDEC  a328-3350 v9383 a<p>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</p>10a3-Iodolawsone10aHydroxynaphthoquinone (HNQ)10aHydroxynaphthosemiquinone radical (HNSQ)10aMagnetic phase transition10aPolymorphs10aValence tautomers1 aZaware, Santosh, B.1 aDagade-Waghmode, Shobha1 aGonnade, Rajesh, G.1 aSrinivas, Darbha1 aRane, Sandhya, Y.  uhttps://library.ncl.res.in/content/magnetic-phase-transition-valence-tautomers-polymorphs-3-iodolawsone-single-crystal-x-ray-0