IR spectroscopic studies on substituted pyridine N-oxide complexes of tin(IV) chloride in acetonitrile

Effects of N‐Oxidation on Heteroaromatic Macrocycles: Synthesis, Electronic Structures, Spectral Properties, and Reactivities of Tetraazaporphyrin meso‐N‐Oxides

“…This increased single‐bond character of the C−N bonds can be attributed to a cross‐conjugated resonance structure with an N=O double bond (Figure c), in which the 18π‐aromatic circuit of the TAP skeleton is disrupted by the oxygen atom. The IR spectrum of 2′H 2 displays an intense absorption band at 1234 cm −1 , assigned to the N−O stretching vibration as commonly seen in pyridine N ‐oxides (Figure S4‐1 in the Supporting Information) …”

“…The IR spectrum of 2'H 2 displays an intense absorptionband at 1234 cm À1 ,assigned to the NÀOstretching vi-brationa sc ommonly seen in pyridine N-oxides ( Figure S4-1 in the SupportingI nformation). [11] Figure 3s hows 1 HNMR spectra of 1H 2 and 2H 2 in CDCl 3 at room temperature. Thei nternal NÀHp rotons, tBu protons, and externalp yrrole b-protons of 1H 2 were observed at À2.40, 2.23, and 8.95 ppm, respectively,c learly indicating the existence of as trong diatropic ring current typical of 18p-aromatic porphyrinoids.…”