Charge-transfer complexes of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone with amino molecules in polar solvents.
The charge-transfer complexes have scientific relevance because this type of molecular interaction is at the basis of the activity of pharmacological compounds and because the absorption bands of the complexes can be used for the quantification of electron donor molecules. This work aims to assess the stability of the charge-transfer complexes between the electron acceptor 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and two drugs, procaine and atenolol, in acetonitrile and ethanol. The stability of DDQ in solution and the time required to obtain the maximum complex formation were evaluated. The stoichiometry and the stability of the complexes were determined, respectively, by Job's plot method and by the elaboration of UV-vis titrations data. The latter task was carried out by using the non-linear global analysis approach to determine the equilibrium constants. This approach to data elaboration allowed us to overcome the disadvantages of the classical linear-regression method, to obtain reliable values of the association constants and to calculate the entire spectra of the complexes. NMR spectra were recorded to identify the portion of the donor molecule that was involved in the interaction. The data support the participation of the aliphatic amino groups in complex formation and exclude the involvement of the aromatic amine present in the procaine molecule.
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy.
Silvia
S
Berto
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy. Electronic address: enrico.chiavazza@unito.it.
Enrico
E
Chiavazza
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy.
Valentina
V
Ribotta
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy.
Pier Giuseppe
PG
Daniele
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy; INSTM and NIS Centre, University of Torino, Via Quarello 15A, 10135 Turin, Italy.
Claudia
C
Barolo
Dept. of Drug Science and Technology, University of Torino, Via Giuria 9, 10125 Turin, Italy.
Agnese
A
Giacomino
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy.
Davide
D
Vione
Dept. of Chemistry, University of Torino, Via P. Giuria 7, 10125 Turin, Italy.
Mery
M
Malandrino
D000097:Acetonitriles / Q000737:chemistry; D000588:Amines / Q000737:chemistry*; D016227:Benzoquinones / Q000737:chemistry*; D004583:Electrons; D000431:Ethanol / Q000737:chemistry; D007700:Kinetics; D066244:Proton Magnetic Resonance Spectroscopy; D012997:Solvents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013997:Time Factors
D000097:Acetonitriles; D000588:Amines; D016227:Benzoquinones; D012997:Solvents; C000928:dichlorodicyanobenzoquinone; D000431:Ethanol; C032159:acetonitrile
Atenolol; CT complexes; DDQ; NMR; Procaine; Spectrophotometry