Artículos de revistas
F-19 chemical shifts, coupling constants and conformational preferences in monosubstituted perfluoroparacyclophanes
Registro en:
Magnetic Resonance In Chemistry. Wiley-blackwell, v. 49, n. 3, n. 93, n. 105, 2011.
0749-1581
WOS:000287890600001
10.1002/mrc.2713
Autor
Ghiviriga, I
Zhang, LH
Martinez, H
Contreras, RH
Tormena, CF
Nodin, L
Dolbier, WR
Institución
Resumen
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In the process of studying the chemistry of perfluoro[2.2]paracyclophanes (PFPCs), a novel class of compounds, it became necessary to identify some disubstituted products. To achieve this goal, we characterize in this work some monosubstituted PFPCs, identifying their F-19-F-19 coupling patterns, and establishing a methodology for the assignment of their F-19 chemical shifts. The pattern of coupling constants indicates a skewed geometry in which the upper deck moves towards or away from the substituent, depending on the substituent electron-donor character and size. Quantum chemical calculations, performed at the HF/6-311 + G(d,p)//B3LYP/EPR-III level of theory, confirmed the conformations inferred from coupling constants and reproduced well the values of the couplings. Transmission mechanisms for the FC term of four- and five-bond F-19-F-19 couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of F-19 chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products. Copyright (C) 2011 John Wiley & Sons, Ltd. 49 3 93 105 CONICET [5119/05] UBACYT [X-047] Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) CONICET [5119/05] UBACYT [X-047] FAPESP [06/03980-2, 08/06282-0]