Solubilities and thermodynamics of TPP in propionic acid + water and TPPMnCl in N,N-dimethylformamide + water solvent mixtures at (303.2–343.2) K
Introduction
5,10,15,20-Tetraphenylporphyrin (TPP) and 5,10,15,20-tetraphenylporphyrin manganese(III) chloride (TPPMnCl), are known as their widely applications in photodynamic therapy agents [1], [2], molecular electronics and sensors [3], [4], functional organic materials [5], non-linear optics [6] and field-effect transistors [7]. In the recent decades, TPPMnCl is widely used as oxidation catalyst [8], [9], [10], [11], [12]. This kind of metal porphyrin gradually taking the place of traditional catalysts in catalyzing the inert hydrocarbon bond, because of its excellent bio-catalytic effect, the catalytic effect of metal porphyrin is the same as that of cytochrome P-450 monooxygenase [13], [14].
The synthetic methods of TPP and TPPMnCl have been well-investigated by many researchers. Usually, TPP is synthesized by the reaction of benzaldehyde with pyrrole at atmospheric pressure [15]. Usually the solvent is propionic acid (abbreviated in PA), TPP and water are the main products. When the reaction is completed, the solution is cooled to room temperature, the main product TPP would crystallized out from the solution. TPPMnCl is synthesized by the reaction of manganese(II) chloride tetrahydrate with TPP under atmospheric pressure [16]. In the manufacturing process of TPPMnCl, usually the solvent is N,N-dimethylformamide (abbreviated in DMF), when the reaction is completed, TPPMnCl must be separated from aqueous DMF. The solution crystallization, which is an important technology to produce crystalline solids from solutions, has a significant effect on the quality of product. The design and operation of the solution crystallization process strongly relies on accurate solubility data, however the solubility is a thermodynamic variable that depends on temperature and the solution composition. To better understand the crystallization process and design an optimum crystallization step for TPP and TPPMnCl, it is crucial to establish the systematic study of solid–liquid equilibrium of TPP in propionic acid + water binary solvent mixtures and TPPMnCl in DMF + water binary solvent mixtures.
According to the above analysis, the solubility characteristics of TPP and TPPMnCl in given solvents have a considerable influence on the design and operation of the solution crystallization process, it is crucial to know the solubility data and thermodynamic parameters of TPP and TPPMnCl. However, until now, there is no experimental data for solubilities of TPP and TPPMnCl in literatures. In our previous work [17], [18], the solubilities of similar compounds such as 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin in propionic acid + water binary solvent mixtures and 5,10,15,20-tetrakis(p-chlorophenyl)porphyrin manganese(III) chloride in N,N-dimethylformamide + water binary solvent mixtures have been measured.
The aim of this work was to investigate the solubilities of TPP in propionic acid + water binary solvent mixtures and TPPMnCl in DMF + water binary solvent mixtures at temperatures ranging from (303.2 to 343.2) K under atmospheric pressure. The modified Apelblat equation was selected to correlate the solubilities of TPP and TPPMnCl with the temperature and solvent composition. At the same time, the thermodynamic parameters including dissolution enthalpy, dissolution entropy, isobaric heat capacity, and Gibbs free energy of TPP and TPPMnCl were obtained by combining both the modified Apelblat equation and Clark–Glew equation.
Section snippets
Materials
TPP (molecular mass 614.74, CAS registry No. 917-23-7, chemical structure shown in Fig. 1 [19], [20]) and TPPMnCl (molecular mass 703.11, CAS registry No. 32195-55-4, chemical structure drawn in Fig. 2 [21], [22], [23]), were synthesized by the method described in detail elsewhere [15], [16], with both the purity of TPP and TPPMnCl greater than 98% in terms of mass fraction. Propionic acid and N,N-dimethylformamide were obtained from Aladdin Chemistry Co., had the declared purity of 99.5% and
Experimental results
The determined solubility of TPP in binary PA + water solvent mixtures and TPPMnCl in binary DMF + water solvent mixtures in terms of mole fraction is defined as:where mTPP, mTPPMnCl, mDMF, mPA and mwater represent the mass of TPP, TPPMnCl, DMF, PA and water in the saturated solution, respectively. MTPP, MTPPMnCl, MDMF, MPA and Mwater are the molecular weight of TPP, TPPMnCl, DMF, PA and water,
Conclusions
In this work, the solubilities of TPP in propionic acid + water solvent mixtures at (303.2–343.2) K and TPPMnCl in DMF + water solvent mixtures at (303.2–343.2) K under atmospheric pressure have been determined. The effects of mole fraction of propionic acid and DMF in the solvent mixtures on the solubility were studied. The following conclusions could be reached: (1) the solubilities of TPP in propionic acid + water solvent mixtures and TPPMnCl in DMF + water solvent mixtures increase with an increase
Acknowledgements
The project was granted financial support from Key S&T Special Project of Zhejiang Province (2012C13007-2), the Fundamental Research Funds for the Central Universities and the National Nature Science Fund (21302049).
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2016, Journal of the Brazilian Chemical Society