Continuous variation method, known as Job plot, is the most commonly applied method for the determination of stoichiometry of complex chemical entities for over 100 years. Although, the method was proven successful in the analysis of very stable metal-ligand complexes, we demonstrate that its use in supramolecular chemistry often provides false results. We support this statement with multiple simulations as well as cases studies of several real host-guest systems. We propose an alternative, general method relying on the analysis of residual distribution in titration data fitting. The latter method is more convenient compared to the Job plot and unlike it gives correct results in all real cases studied.

ABSTRACT:A contemporary synthetic route, starting from the bioactive compound via the corresponding glycidyl ester and β-substituted β-lactone to (homo)-and (co)oligoesters with a bioactive moiety covalently linked as pendent groups along an oligomer backbone, was reported.The bioactive compounds were selected from antioxidants used in cosmetics. Two models of bioactive (homo)-and (co)oligoesters were synthesized via anionic ring-opening (co)oligomerization of p-methoxybenzoyloxymethylpropiolactone (p-AA-CH 2 -PL) initiated by p-anisic acid sodium salt. An analytical protocol was developed for a detailed structural characterization at the molecular level of these bioactive (co)oligoesters. The molecular level structure of the obtained bioactive (homo)-and (co)oligoesters was established by electrospray ionization tandem mass spectrometry (ESI-MS/MS) supported by 1 H NMR analysis.Additionally, the results presented here are important for the analysis of designed biodegradable polymeric controlled-release systems of bioactive compounds with potential applications in cosmetology.1

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