X-RAY CRYSTAL STRUCTURE, DIPOLE MOMENT AND THEORETICAL MOLECULAR ORBITAL STUDY OF 5-NITRO-2- (2-PYRIDINYLTHIO)-PYRIDINE

Abstract

The conformational aspects of 5-nitro-2-(2-pyridinylthio)-pyridine were investigated in the three States of matter. The experimentally derived conformers using the analytical methods (X-ray diffraction, dipolometry) are compared with theoretical MO calculations (AM-1 method). Crystals are monoclinic, with unit cell dimensions a = 6.081(5), b = 15.131(8), c = 22.549(10) Å; β=93.40(5)° space group P2₁/c. The structure was determined from 2243 three dimensional counter data and refined to convergence factor values of R = 0.08. Two independent molecules (A and B) there are per asymmetric unit, which are similar as concern the bond lengths and angles close to usual standard values. In both A and B The 5-nitro-pyridine ring (bearing nitrogen atom N(2)) is rotated out by 12° of coplanarity with C-S-C plane, while the pyridine ring (bearing nitrogen atom N(1)) is twisted, in a disrotatory way, by 41.7° (A) and 59.7° (B). The relative orientations of the ring nitrogen atoms with respect to the C-S-C angle, are N(1), N(Z)-outside and N(1)-inside N(2)-outside, in A and B, respectively. The dipole moment analysis indicates that the twisted conformation of the solid A should be retained in solution. The twisted conformations in the solid and in solution do not parallel the minimum energy conformation calculated for the isolated molecule by AM-1 method, in which the two rings are rotated in opposite directions out of the all-planar N(1), N(2)-inside conformation by 36° (5-nitro-pyridine ring) and 54° (pyridine ring).

Key Words:

• 5-Nitro-2-(2-pyridinylthio)-pyridine
• X-Ray-diffraction
• dipole moment
• MO-calculations.