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Solvent and temperature effects on the conformational equilibria of a dihydrobenzo[h]quinolinium fluoroborate.
Caroli Rezende, Marcos; Guerrero, Juan.
Affiliation
  • Caroli Rezende M; Facultad de Química y Biología, Universidad de Santiago de Chile, Casilla 40, Correo 33, Santiago, Chile. marcos.caroli@usach.cl
Magn Reson Chem ; 47(6): 505-10, 2009 Jun.
Article in En | MEDLINE | ID: mdl-19333971
Spectra of the N-phenyl-5,6-dihydro-2,4-diphenylbenzo[h]quinolinium tetrafluoroborate (1) and of the N-phenyl-5,6,8,9-tetrahydro-7-phenyldibenzo[c,h]acridinium tetrafluoroborate (2) were recorded in various solvents and temperatures. The analysis of the (1)H-NMR spectra of the tetrafluoroborate salt 1, recorded in acetone, acetonitrile, 1,1,2,2-tetrachloroethane and chloroform, revealed the existence of an equilibrium between two conformers in solution. Tight ion-pairing in chloroform led to a smaller barrier for interconversion between the two conformers. In more polar solvents, where the dihydrobenzoquinolinium exists as a free cation, theoretical calculations predicted larger barriers. The spectra of 1 in 1,1,2,2-tetrachloroethane also varied with temperature, resembling at higher temperatures the spectrum in CDCl(3) and at 300K spectra in more polar media. Spectra of 2 did not vary with the solvent or the temperature, in an indication of a much higher barrier to conformational interconversion, because of a greater steric hindrance between the N-phenyl substituent and the dihydrobenzo rings.
Subject(s)

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Acetone / Acetonitriles / Quinolinium Compounds / Temperature / Chloroform / Ethane / Hydrocarbons, Chlorinated Language: En Journal: Magn Reson Chem Journal subject: QUIMICA Year: 2009 Document type: Article Affiliation country: Chile Country of publication: United kingdom

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Acetone / Acetonitriles / Quinolinium Compounds / Temperature / Chloroform / Ethane / Hydrocarbons, Chlorinated Language: En Journal: Magn Reson Chem Journal subject: QUIMICA Year: 2009 Document type: Article Affiliation country: Chile Country of publication: United kingdom