UV–Vis spectroscopic study of preferential solvation and intermolecular interactions in methanol/1-propanol/acetonitrile by means of solvatochromic probes Nélson Nunes a,b , Ruben Elvas-Leitão a,b , Filomena Martins b,⇑ a Área Departamental de Engenharia Química, Instituto Superior de Engenharia de Lisboa (ISEL), Instituto Politécnico de Lisboa, R. Conselheiro Emídio Navarro, 1, 1959-007 Lisboa, Portugal b Centro de Química e Bioquímica (CQB), Departamento de Química e Bioquímica, Faculdade de Ciências, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016 Lisboa, Portugal highlights  Four solvatochromic probes were modeled by a preferential solvation model in MeOH/1-PrOH/MeCN.  Synergistic effects and solvent ‘‘complexes’’ were identified.  Solvation ‘‘scales’’ for each probe in the binary and ternary mixtures were set up.  a, b, and p  values were obtained in the ternary mixture.  Probe/solvent/solvent interactions were characterized and rationalized. graphical abstract π *average average average article info Article history: Received 13 November 2013 Received in revised form 9 January 2014 Accepted 12 January 2014 Available online 18 January 2014 Keywords: Solvatochromic probes Kamlet–Taft parameters Solvent exchange model Preferential solvation Ternary mixture abstract Solvatochromic UV–Vis shifts of four indicators (4-nitroaniline, 4-nitroanisole, 4-nitrophenol and N,N- dimethyl-4-nitroaniline) have been measured at 298.15 K in the ternary mixture methanol/1-propanol/ acetonitrile (MeOH/1-PrOH/MeCN) in a total of 22 mole fractions, along with 18 additional mole fractions for each of the corresponding binary mixtures, MeOH/1-PrOH, 1-PrOH/MeCN and MeOH/MeCN. These values, combined with our previous experimental results for 2,6-diphenyl-4-(2,4,6-triphenylpyridini- um-1-yl)phenolate (Reichardt’s betaine dye) in the same mixtures, permitted the computation of the Kamlet–Taft solvent parameters, a, b, and p * . The rationalization of the spectroscopic behavior of each probe within each mixture’s whole mole fraction range was achieved through the use of the Bosch and Rosés preferential solvation model. The applied model allowed the identification of synergistic behaviors in MeCN/alcohol mixtures and thus to infer the existence of solvent complexes in solution. Also, the addition of small amounts of MeCN to the binary mixtures was seen to cause a significant var- iation in p * , whereas the addition of alcohol to MeCN mixtures always lead to a sudden change in a and b. The behavior of these parameters in the ternary mixture was shown to be mainly determined by the con- tributions of the underlying binary mixtures. Ó 2014 Elsevier B.V. All rights reserved. Introduction The use of electronic spectroscopy for the characterization of pure solvents through solvatochromic probes has been extensively performed over the last decades, but fewer studies involved two sol- vents and even fewer addressed three or more component solutions [1–7]. The relevance of solvent mixtures becomes obvious consider- ing their range of applications, which include modifications of sol- utes’ solubility, tuning of solution physicochemical properties such as viscosity or polarity, and their use in separation processes like, for instance, in liquid chromatography, just to mention a few. 1386-1425/$ - see front matter Ó 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2014.01.021 ⇑ Corresponding author. Tel.: +351 21 7500870; fax: +351 21 7500088. E-mail address: filomena.martins@fc.ul.pt (F. Martins). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 124 (2014) 470–479 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa