The Rotational Zeeman Effect of Pyrazole and Imidazole

Abstract

The rotational Zeeman effect of the most abundant isotopic species of pyrazole and of imidazole has been studied under AM=Q and AM = ± 1 selection rules. With field close to 1.9 Tesla, the nuclear Zeeman effect uncouples the rotational angular momentum and the spins of the two nonequivalent l4 N quadrupole nuclei. The observed ^-tensor elements are g aa = -0.07498 (14), g hh = -0.12531(13), and g cc = 0.06346 (12) The so-called nonlocal (n-ring current) contributions to the out of plane components of the susceptibility tensor, / f n°nlocal , derived as differences between the observed susceptibilities and values calculated from additivity rules for local atom susceptibilities, are compared to those derived earlier for other aromatic five membered ring molecules.

Tautomerism and Microsolvation in 2-Hydroxypyridine/2-Pyridone

“…16,39,40 In contrast, pyridinic nitrogens have positive values of cc . 16,40,41 The experimental values of -2.18 and 1.993 MHz in Table 1 allow us to establish unambiguously the presence of the keto and enol tautomers, respectively, and the conclusive identification of the 2PO-H 2 O and 2HP-H 2 O monohydrates in our supersonic expansion. The difference in the nature of the 14 N nucleus is reflected in the different hyperfine structure pattern for the 2PO-H 2 O and 2HP-H 2 O complexes (see Figure 1).…”

Halogen bonding properties of 4-iodopyrazole and 4-bromopyrazole explored by rotational spectroscopy and ab initio calculations

“…7 Rotational spectroscopy can be used to provide information about the geometric and electronic structures of molecules. Microwave spectra have previously been reported for the isolated pyrazole molecule in the gas-phase [8][9][10][11][12][13][14] and also for derivatives and complexes. [15][16][17] This report describes the pure rotational spectra of 4-bromo-and 4-iodopyrazole, which have been recorded for the first time.…”

Quadrupole and Octopole Moments of Heteroaromatic Rings

“…We report systematic ab initio second-order Møller−Plesset (MP2) calculations of the quadrupole and octopole moments of 36 planar heteroaromatic monocycles: benzene, 12 azines, pyrrole, 9 azoles, furan, 9 oxazoles, borazine, boroxine, and 1,2,4,3,5-trioxadiborole (B 2 H 2 O 3 ). Experimental measurements and/or electron-correlated calculations of quadrupole moments have been reported previously for only 15 of these important molecules, ,− and we are unaware of any such work for octopole moments of these heterocycles.…”