Observation and characterization by 15N CPMAS NMR of a double proton transfer in cyclic dimers of 15N, 15N′-di(4-bromophenyl)-formamidine in the solid state

✍ Scribed by Ferdinand Männle; Iwona Wawer; Hans-Heinrich Limbach

• Publisher: Elsevier Science
• Year: 1996
• Tongue: English
• Weight: 378 KB
• Volume: 256
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(96)00511-8

✦ Synopsis

Using dynamic 15N CPMAS NMR spectroscopy a novel double proton transfer was detected in the cyclic hydrogen bonded dimers of polycrystalline tSN,ZSN'-di-(4-bromophenyl)-formamidine. Rate constants of this process, which is degenerate within the margin of error, were obtained by lineshape (kl2 = 10 6.6 exp(-9.7 kJ mol I/RT) s l, 110 K < T< 142 K) and 15N T 1 data analysis (minimum at 324 K and 9.12 MHz, IH-~SN distance rHN = 1.1 1 ,~, kl2 = 101°9 × exp( -21.5 kJ mol -~/RT) s-l, 240 K ~ T < 370 K). The non-Arrhenius behavior observed indicates proton tunneling at low temperatures.