Rosa Cristina Moutinho Ferreira

Heterocyclic amino acids as fluorescent reporters for transition metals: synthesis and evaluation of novel furyl-benzoxazol-5-yl-L-alanines

Unnatural alanine derivatives bearing a benzoxazole moiety at the side chain, acting simultaneously as the coordinating and reporting unit, via fluorescence changes, were synthesised with a furan ring at position 2, substituted with different (hetero)aryl substituents, in order to tune the photophysical and chemosensory properties of the resulting compounds. The amino acid derivatives were prepared in protected form at their N- and C-termini with tert-butoxycarbonyl urethane and methyl ester protecting groups, respectively. The novel furyl-benzoxazol-5-yl-L-alanines were evaluated for the first time in the recognition of several transition metal cations with environmental, medicinal and analytical interest such as Co2+, Cu2+, Zn2+ and Ni2+, in acetonitrile solution. The spectrofluorimetric titrations showed that the novel benzoxazolyl-alanines 3a–g were sensitive, although not selective, fluorimetric chemosensors for the above mentioned cations, with the best result being obtained for N,N-diethylamino substituted alanine 3d in the sensing of Cu2+. The heterocyclic system at the side chain was identified as the key factor in the recognition event of the metal cations, through its electron donor atoms. The encouraging photophysical and metal ion sensing properties of these furyl-benzoxazolyl-alanines suggest that they can be used to obtain bioinspired fluorescent reporters for metal ions such as peptides/proteins with chemosensory/probing abilities.

Fluorescent phenanthroimidazoles functionalized with heterocyclic spacers: synthesis, optical chemosensory ability and two-photon absorption (TPA) properties

Three series of fluorescent phenanthroimidazoles bearing heterocyclic spacers were synthesized in moderate to excellent yields and evaluated as optical chemosensors for ions as well as two-photon absorbing chromophores. Interaction of compounds 5–7 with anions and cations in acetonitrile and acetonitrile/H2O (95 : 5) showed them to be selective receptors for several anions (AcO−, CN− and F−) and cations (Fe3+, Cu2+ and Pd2+), with compound 7a being the most sensitive receptor for Fe3+ and Cu2+. On the other hand, compounds 5a, 7b and 7c were the most sensitive receptors for AcO−, CN− and F−. The binding stoichiometry between the receptors and the anions and cations was found to be 1 : 2 (ligand to anion/metal cation). The binding process was also followed by 1H NMR titrations. The evaluation of the TPA properties of chosen phenanthroimidazoles 7a–c by the two-photon induced fluorescence method revealed that compound 7c, which contains a bithienyl spacer, exhibited the highest TPA cross-section (σ2) value.

Novel alanines bearing a heteroaromatic side chain: synthesis and studies on fluorescent chemosensing of metal cations with biological relevance

Abstract A family of novel thienylbenzoxazol-5-yl-l-alanines, consisting of an alanine core bearing a benzoxazole at the side chain with a thiophene ring at position 2, substituted with different (hetero)aryl substituents, was synthesised to study the tuning of the photophysical and chemosensory properties of the resulting compounds. These novel heterocyclic alanines 3a–f and a series of structurally related bis-thienylbenzoxazolyl-alanines 3g–j were evaluated for the first time in the recognition of selected metal cations with environmental, medicinal and analytical interest such as Co2+, Cu2+, Zn2+ and Ni2+, in acetonitrile solution, with the heterocycles at the side chain acting simultaneously as the coordinating and reporting units, via fluorescence changes. This behaviour can be explained by the involvement of the electron donor heteroatoms in the recognition event, through complexation of the metal cations. The spectrofluorimetric titrations showed that thienylbenzoxazolyl-alanines 3a–j and 4a,b were non-selective fluorimetric chemosensors for the above-mentioned cations, with the best results being obtained for the interaction of Cu2+ with bis-alanine 3j and deprotected alanines 4a,b. The encouraging photophysical and metal ion sensing properties of these thienylbenzoxazolyl-alanines suggest that they can be used to obtain bioinspired fluorescent reporters for metal ion such as peptides/proteins with chemosensory/probing ability.

Synthesis, characterization and ion sensing properties of a new colorimetric chemosensor based on an hydrazone moiety

Resumo da comunicacao eletronica apresentada na 21st International Electronic Conference on Synthetic Organic Chemistry, 1–30 November 2017; Sciforum Electronic Conference Series, Vol. 21.

Heterocyclic imidazo-anthraquinone as an optical sensor: synthesis, characterization and evaluation of the chemosensory ability

Fundacao para a Ciencia e Tecnologia (Portugal) and FEDER-COMPETE for financial support through Centro de Quimica (UID/QUI/00686/2013 and UID/ QUI/0686/2016), and a PhD grant to R.C.M. Ferreira (SFRH/BD/86408/2012). The NMR spectrometer Bruker Avance III 400 is part of the National NMR Network and was purchased with funds from FCT and FEDER