Internal and External Implications of the Structure of Hydrogen Bonded Complexes . Ii. Mndo‐pm3 Studies on the Structure of the 4‐methylpyridine Complex With Pentachlorophenol

Abstract

The structure of the complex of 4-methylpyridine with pentachlorophenol in the gas phase was determined by the MNDO-PM3 procedure and compared with the experimental crystallographic structure. The calculated potential for internal rotation around the hydrogen bond axis predicts a free rotation in the gas phase and a large ability of the complex to adapt its shape to the requirements of the crystal packing. The influence of different internal and external factors on the structure of the studied complex is discussed.

1H-MAS-NMR Chemical Shifts in Hydrogen-Bonded Complexes of Chlorophenols (Pentachlorophenol, 2,4,6-Trichlorophenol, 2,6-Dichlorophenol, 3,5-Dichlorophenol, and p-Chlorophenol) and Amine, and H/D Isotope Effects on 1H-MAS-NMR Spectra

“…The result obtained in the PCP complexes is consistent with the inversion point of 35 Cl NQR frequencies [ 12 , 28 ]. In PCP–4MP, a proton transfer and isotope polymorphism have been reported [ 12 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. Since the large 1 H-NMR CS value of 18.6 ppm was recorded in TCP–IMID as compared with 17.8 ppm of PCP–4MP, it can be expected that the similar properties are obtained in TCP–IMID.…”

“…In a case of pentachlorophenol (abbreviated to PCP) complexes, it has been reported that PCP forms salts with nitrogen-bases (N-Base) covering a broad p K a range (0.65–11.20). These crystals have been employed to detect proton-transfer equilibrium between O–H···N (covalent form) and O − ···H–N + (ionic form) [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 ]. 35 Cl NQR frequency measurements have reported that the NQR frequencies give constant values of ca .…”