SPECTROSCOPIC CHARACTERIZATION AND AB INITIO CALCULATIONS OF NEW DIAZAPHOSPHOLE AND DIAZAPHOSPHORINANE

Phosphoryl chloride is used as a starting material to synthesize new diazaphosphole, 4-OCH3-C6H4NHP(O)[4-CH3-NH-C6H3-HN] ( 1) and diazaphosphorinane, 4-OCH3-C6H4NHP(O)[NH-C10H6-NH] ( 2). The products are characterized by H-1, C-13, P-31 NMR, and IR spectroscopy. A high value (2)J(PNH) = 17.0 Hz, 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 (2)J(P, C) as well as two (3)J(P, C) in the C-13 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 P-31 NMR spectra reveal that delta(P-31) 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 Delta E-stabilization = E-molecule - Sigma E-i, where i = atom. To obtain the atomic hybridizations, NBO computations are made at the B3LYP/6-31+G** level. Also, by NMR calculations the H-1, C-13, P-31 chemical shifts are obtained and compared with the experimental ones.