title: SOM assembly of hydroxynaphthoquinone and its oxime: polymorphic X-ray structures and EPR studies.
abstract: Investigation on solvent-induced polymorphism in X-ray structures of 2-hydroxy-1,4-naphthoquinone (Lawsone) 1, is carried out. In protic methanol, 1 crystallizes in monoclinic space group P2(1)/c (1a) comprising of 2D hydrogen bonded network via cyclic dimers. In aprotic solvent such as acetone on the other hand, 1 exhibits orthorhombic space group Pna 2(1) (1b) and emerges with 1D catemeric chain. Solvent-induced topological isomerism of cyclic dimers and helical catemeric chains arising from (i) bifurcated intra- and inter molecular hydrogen bondings viz. O-H...O=C interactions between C(2) hydroxyl and C(1), C(4) carbonyls, (ii) C-H...O interactions viz. C(3)-H...O(1)C(1) have been discussed. A signal for radical in 1 at g = 2.0058 is signatured by EPR spectrum and it's oxime derivative viz. 2-hydroxy-4-naphthoquinone-1-oxime 2, in solid state shows biradical and monoradical formation with aggregation of dimer and monomer due to non-covalent hydrogen bonds. Zero field split parameters for 2 are estimated to be D = 215 G, Ex = 13 G, Ey = 47 G at 298 K. A half field signal at 77 K indicates triplet ground state. Frozen glass EPR of 2 resolves as regioregular dimeric-monomeric species showing hyperfine interactions with 1-oximino nitrogen in dimer A (14N) = 15.5 G].
authors.affiliation: Department of Chemistry, University of Pune, Pune 411007, India.
authors.forename: Ashwini V
authors.initials: AV
authors.lastname: Todkary
authors.forename: Rupali
authors.initials: R
authors.lastname: Dalvi
authors.forename: Sunita
authors.initials: S
authors.lastname: Salunke-Gawali
authors.forename: Jorge
authors.initials: J
authors.lastname: Linares
authors.forename: François
authors.initials: F
authors.lastname: Varret
authors.forename: Jérôme
authors.initials: J
authors.lastname: Marrot
authors.forename: Jatinder V
authors.initials: JV
authors.lastname: Yakhmi
authors.forename: Mohan
authors.initials: M
authors.lastname: Bhadbhade
authors.forename: D
authors.initials: D
authors.lastname: Srinivas
authors.forename: Shridhar P
authors.initials: SP
authors.lastname: Gejji
authors.forename: Sandhya Y
authors.initials: SY
authors.lastname: Rane
mesh_terms: D000096:Acetone / Q000737:chemistry; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D009285:Naphthoquinones / Q000737:chemistry*; D010091:Oximes / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry
chemical_list: D009285:Naphthoquinones; D010091:Oximes; D012997:Solvents; D000096:Acetone; C005090:lawsone; D000432:Methanol