A conformational analysis of the six isomers of oxybispyridine

Abstract

Conformational energy contour maps of the six isomers of oxybispyridine have been constructed using the ab initio STO‐3G molecular orbital method. The calculations (employing a partial rigid rotor) for all six isomers indicate that the minimum energy conformers are not planar and that energy barriers between 70–1000 kJ mol−1 restrict interconversion to planar structures, thereby preventing conjugation between the p‐electrons of the oxygen atom with the π system of the pyridine rings. It is postulated that of the three mechanisms used to explain conformer interconversion about the CO bond, the disrotatory one‐ring flip mechanism is the most appropriate, since the “Morino's” structures are all within 2.5 kJ mol−1 of the minimum. Furthermore, room temperature accessibility of the “Morino's” structures suggests that the Smiles rearrangement would be possible for suitably substituted derivatives of these isomers.

Anions as Connectors for Higher Dimensions. Silver(I) Trifuoracetate with 3,3'-Oxybispyridine vs 3,3'-Thiobispyridine

“…3,3'-Py2O and 3,3'-Py2S are similar noninnocent spacers that possess stable skewed conformers with nonrigid interannular dihedral angles between two pyridyl groups. 27,28 As expected, the reactions of AgCF 3 CO 2 with the spacers basically afford the similar single strands. A striking feature is that the single strands are significantly bridged via the trifluoroacetate anions to give unique 2D grids in contrast to our previous triflate analogs.…”

“…The intrinsic properties of spacers seem to trigger the delicate difference of the "noncovalent anionbridge" There are actual differences between the two spacers in the size, the bond angle, the lone-pair delocalization of chalcogens, the conformational energy barrier, and the donating ability of nitrogen atoms. 17,27,28 Thus, for the present structures, the C-S-C angle of 3,3'-Py2S is smaller than the corresponding value of 3,3'-Py2O. The difference in donating ability between the spacer ligands exists in the structures.…”

Molecular Strands and Related Properties of Silver(Ⅰ) Triflate with 3,3'-Oxybispyridine vs 3,3'-Thiobispyridine

“…Second, the conformational energy barrier of 3,3'-Py 2 S is slightly different from that of 3,3'-Py 2 O. 31,32 The low energy barrier seems to be an unfavorable factor in the formation of crowded coordination. Third, the coordination numbers of each Ag(I) ion may be induced by the donating ability of the spacer ligands.…”