Molecular complexes of explosives with cyclodextrins I. Characterization of complexes with the nitramines RDX, HMX and TNAZ in solution by 1H NMR spin‐lattice relaxation time measurements

Abstract

AbstractInclusion complex formation between the explosive molecules of the nitramine type, RDX, HMX and TNAZ, and cyclodextrins (α, β and γ) was studied in aqueous solution by means of 1H spin–lattice relaxation time (T1) measurements. The results show that nitramines bind to cyclodextrins in solution; RDX and HMX bind most strongly to γ‐cyclodextrin whereas TNAZ binds most strongly to β‐cyclodextrin. The dynamic coupling coefficient and dissociation constant were determined for the complex of TNAZ with β‐cyclodextrin. The values obtained suggest that TNAZ forms a relatively weak complex with β‐cyclodextrin (Kd = 1.8 × 10−2 M) that displays considerable motion in the complex with respect to cyclodextrin (coupling coefficient = 0.23). This method of using 1H T1 measurements for characterizing complex formation in solution, while limited to guest molecules containing a pair of protons having a fixed internuclear distance, is shown to be useful when complexation‐induced chemical shifts are too small to be significant.