Anionic adducts of 1,3,5-trinitrobenzene (TNB) with deprotonated pyrrolidine (Pyr), imidazole (Im), acetone (Ac) and acetylacetone (Acac) have been delivered into the gas phase by electrospray ionization.The so-formed ions, TNB-Nu−(Nu = Pyr, Im, Ac, Acac), have been interrogated by IRMPD spectroscopy inthe fingerprint range. DFT calculations at B3LYP/6-311++G(d,p) level have been performed for a survey of candidate structures. All adducts conform to anionic sigma-complexes (Meisenheimer complexes). The symmetric stretching modes of the nitro groups yield a dominant vibrational signature at 1200–1250 cm−1,the red-shift with respect to the degenerate frequency of 1367 cm−1 in neutral TNB reflecting the extent of negative charge delocalization. The enol complexes TNB-Ac− and TNB-Acac− are largely representedby C-bonded species.
Vibrational signatures of gaseous Meisenheimer complexes bonded at carbon and nitrogen / Chiavarino, Barbara; Crestoni, Maria Elisa; Fornarini, Simonetta. - In: INTERNATIONAL JOURNAL OF MASS SPECTROMETRY. - ISSN 1387-3806. - STAMPA. - 418:(2017), pp. 173-179. [10.1016/j.ijms.2016.09.012]
Vibrational signatures of gaseous Meisenheimer complexes bonded at carbon and nitrogen
Barbara Chiavarino;Maria Elisa Crestoni;Simonetta Fornarini
2017
Abstract
Anionic adducts of 1,3,5-trinitrobenzene (TNB) with deprotonated pyrrolidine (Pyr), imidazole (Im), acetone (Ac) and acetylacetone (Acac) have been delivered into the gas phase by electrospray ionization.The so-formed ions, TNB-Nu−(Nu = Pyr, Im, Ac, Acac), have been interrogated by IRMPD spectroscopy inthe fingerprint range. DFT calculations at B3LYP/6-311++G(d,p) level have been performed for a survey of candidate structures. All adducts conform to anionic sigma-complexes (Meisenheimer complexes). The symmetric stretching modes of the nitro groups yield a dominant vibrational signature at 1200–1250 cm−1,the red-shift with respect to the degenerate frequency of 1367 cm−1 in neutral TNB reflecting the extent of negative charge delocalization. The enol complexes TNB-Ac− and TNB-Acac− are largely representedby C-bonded species.File | Dimensione | Formato | |
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