Syntheses of intercalation compounds of tetraamine in α-Zr(HPO4)2·H2O and the structures of guest molecules by solid state NMR

Abstract

Conformational change of N,N′-Bis-(3-aminopropyl)-1,3-propanediamine (3P4A) intercalated in α-zirconium phosphate (α-ZrP) is reported. It is demonstrated that two kinds of intercalation compounds with different interlayer spacings, i.e., d=2.0 nm and d=1.7 nm, can be isolated by reacting at ca. 333 K and at ca. 298 K in aqueous suspension of 3P4A and α-ZrP, respectively. The lineshape analysis of 13C CP/MAS NMR spectra suggests that the conformation of 3P4A assumes the ‘straight’ form in the higher temperature product while it assumes the ‘bent’ form in the lower temperature product. According to this model, 31P MAS NMR spectra can be consistently assigned. It is found that 31P chemical shift values strongly depend on the bonding state of the amine groups in 3P4A molecule to the phosphate groups of α-ZrP. It is also shown that removing and/or controlling the amount of water molecules in the intercalation compounds are very important for the detailed assignment of the complicated 31P resonances.