Pulsed NMR study of molecular motions and phase transitions in [N(CH3)4]PbX3 (XCl, Br, I)

✍ Scribed by D. Vijayaraghavan; J. Ramakrishna

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 715 KB
• Volume: 49
• Category: Article
• ISSN: 1386-1425
• DOI: 10.1016/0584-8539(93)80071-h

✦ Synopsis

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-Proton spin-lattice relaxation time (TJ is measured in [N(CH,),]PbX, (X=Cl, Br, I) from 3CKt-77 K at 9.75 Ml-lx. All the compounds show discontinuous changes in Ti values (at 256,270 and 277 K, respectively), indicating phase transitions. Single Tr minimum is observed in all the cases and the T, variation is explained in terms of [N(CH3)d and CH, group dynamics. lhe activation energy E, decreases from chloride to iodide (from 4 to 2 kcal/mol). In bromide and iodide, rt is found to decrease with increase in temperature at higher temperatures, indicating the presence of spin-rotation interaction. INTR~DuCDON RECENTLY, there has been considerable interest in ABX3 compounds, where A is NH,, NCH3).d, W-W&),1, PJHKH I 3 or a monovalent metal, B is a divalent metal like Zn,