SPECTROSCOPIC CHARACTERIZATION AND AB INITIO CALCULATIONS OF NEW DIAZAPHOSPHOLE AND DIAZAPHOSPHORINANE
F. Afshar1, Z. Shariatinia2, K. Zare3, F. Ghaziany4
1 PhD student, Science and Research Branch, Islamic Azad University (IAU)
2 Department of Chemistry Amirkabir University of Technology
3 PhD student, Science and Research Branch, Islamic Azad University (IAU) Department of Chemistry Shahid Beheshty University
4 Department of Chemistry Faculty of Sciences, Tarbiat Modares University
fzafshar@yahoo.com
Keywords: diazaphosphole, diazaphosphorinane, 1H, 13C, 31P NMR, ab initio calculations
Pages: 297-304
Abstract
Phosphoryl chloride is used as a starting material to synthesize new diazaphosphole, (1) and diazaphosphorinane, (2). The products are characterized by 1H, 13C, 31P NMR and IR spectroscopy. A high value 2J(PNH) = 17.0, 17.2 Hz is measured for two non-equivalent NH protons of endocyclic nitrogen atoms in compound 1, while it greatly decreases to 4.5 Hz in 2. Also, great amounts are obtained for two 2J(P,C) as well as two 3J(P,C) in the 13C NMR spectrum of 1, but they are zero in 2. Here, the effect of ring strain and ring size on the structural and spectroscopic parameters is observed. The 31P NMR spectra reveal that δ(31P) of compound 1 is far much more downfield (12.63 ppm) relative to that of compound 2 (-10.39 ppm). Furthermore, ab initio quantum chemical calculations are performed to optimize the structures of these molecules by density functional theory (B3LYP) and Hartree-Fock (HF) methods, using the standard 6-31+G** basis set. The stabilization energies are calculated by the equation ΔEstabilization = Emolecule - ∑Ei, where i = atom. To obtain the atomic hybridizations, NBO computations are made at the B3LYP/6-31+G** level. Also, by NMR calculations the 1H, 13C, 31P chemical shifts are obtained and compared with the experimental ones.
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