Infrared, ¹H and ¹³C NMR spectra, structural charcterization and DFT calculations of novel adenine-cyclodiphosp(V)azane derivatives

Adenine tetrachlorocyclodiphospha(V)zane derivatives (III_a-c) were prepared by the reaction of hexachlorocyclodiphospha(V)zane derivatives (I_a-c) and adenine (II) as precursors. The synthesized compound's and their structures (III_a-c) were firmly characterized (based on the presence of an inversion center) using FT-IR (4000-200 cm^-1), UV-vis. (190-800 nm), ¹H, ¹³C NMR and Mass spectral measurements in addition to C, H, N, P elemental analysis. The compounds (III_a-c) were found to be a 1:2 molar ratio of (I_a-c) and adenine (II) adducts, respectively. Confident and complete vibrational assignments are proposed for nearly all fundamental vibrations, along with detailed interpretation for all observed signals in both ¹H and ¹³C NMR spectra of the investigated phospha(V)zanes (III_a-c). In addition, unconstrained geometry optimization of III_a-c were carried out by means of DFT-B3LYP/3-21G(d) calculations to provide new insight into the structural parameters and molecular geometries of compounds III_a-c. The results are reported herein and compared with similar molecules whenever appropriate.