SOM assembly of hydroxynaphthoquinone and its oxime: polymorphic X-ray structures and EPR studies.
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].
Todkary
Ashwini V
AV
Department of Chemistry, University of Pune, Pune 411007, India.
Dalvi
Rupali
R
Salunke-Gawali
Sunita
S
Linares
Jorge
J
Varret
François
F
Marrot
Jérôme
J
Yakhmi
Jatinder V
JV
Bhadbhade
Mohan
M
Srinivas
D
D
Gejji
Shridhar P
SP
Rane
Sandhya Y
SY
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
D009285:Naphthoquinones; D010091:Oximes; D012997:Solvents; D000096:Acetone; C005090:lawsone; D000432:Methanol