Desired form of polymorphism of 6-chloro-2,4-dinitroaniline crystals grown by controlled growth temperature in melt growth
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In this paper, the important form of a polymorphism of 6-chloro-2,4-dinitroaniline (CDA) crystals grown by the melt growth technique and its structure, physical, properties were discussed. Single crystals of form II and form III were grown by spontaneous nucleation of CDA melt. Unit cell parameters of these two forms were determined by the single-crystal X-ray diffraction technique. A powder X-ray diffraction pattern obtained from single-crystal data was compared with the experimental pattern. Functional groups presented in the molecules were identified by FTIR spectra, and packing difference between the two forms was realized by splitting of the absorption band and inter- and intramolecular interaction. DSC and TG/DTA analyses confirmed that each form has its own melting peak around 160 (form II) and 162 °C (form III) and there is no phase transition occurring between these forms. Harmonic vibrational frequency (β) of CDA was evaluated theoretically using HF/6-31G level and this value was compared with the experimental Kurtz–Perry technique. The calculated HOMO-LUMO energy shows that charge transfer occurred within the molecules.
KeywordsPolymorphism Melt growth Powder X-ray diffraction Thermal analysis Hyperpolarizability
The authors are grateful to DRDO–ERIP, New Delhi, for financial assistance under the major research project. We thank Prof. P. K. Das, Indian Institute of Science, Bangalore, for support in the SHG measurement and SAIF-IIT Madras for X-ray diffraction and thermal analysis.
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