Flor Rodríguez-Prieto

• PhD
• Professor (Full) at University of Santiago de Compostela

Alzheimer’s disease (AD) is a major public health challenge in ageing societies, with its onset occurring years before symptoms appear. In recent decades, growing evidence has identified soluble amyloid-β (Aβ) oligomers as key species in the pathogenesis and diagnosis of AD, underscoring the urgent need for early detection methods. Fluorescence spe...

Alzheimer’s disease (AD) is a major public health challenge in ageing societies, with its onset occurring years before symptoms appear. In recent decades, growing evidence has identified soluble amyloid-β (Aβ) oligomers as key species in the pathogenesis and diagnosis of AD, underscoring the urgent need for an early detection of these oligomers. Cu...

Guanine quadruplexes (G4s) are highly polymorphic four-stranded structures formed within guanine-rich DNA and RNA sequences that play a crucial role in biological processes. The recent discovery of the first G4 structures within mitochondrial DNA has led to a small revolution in the field. In particular, the G-rich conserved sequence block II (CSB...

2-Cyano-6-hydroxybenzothiazole (CBTOH) is a key intermediate in the biosynthesis of D-luciferin, also used for its chemical synthesis and as luciferin bioluminescence precursor for chemical analysis. We characterized CBTOH and its O-methylated derivative by UV-vis absorption, by steady-state and time-resolved fluorescence spectroscopy, and by densi...

The singlet excited-state of the N-methylquinolinium cation (MQ+) is a strong oxidant commonly used as photosensitizer, whose fluorescence is therefore quenched by electron donors. Interestingly, the fluorescence of MQ+ is also quenched by hydroxy compounds such as water and alcohols, more difficult to oxidize. We investigated the quenching mechani...

We studied the excited-state behavior of a family of mono- and diprotonated derivatives of 2-phenylbenzimidazole in different solvents, using steady-state and time-resolved fluorescence spectroscopy. The species investigated were 2-(4'-amino-2'-hydroxyphenyl)benzimidazole (1), the diethylamino analogue 2-(4'-N,N-diethylamino-2'-hydroxyphenyl)benzim...

Guanine-rich DNA and RNA sequences can adopt highly polymorphic four-stranded structures, so-called G-quadruplexes (GQs), which play an important role in different biological processes such as telomere maintenance, abortive transcription and gene regulation. Their biological relevance has increased the interest in the development of probes to sense...

The aggregation of amyloid-β peptide and its accumulation in the human brain has an important role in the etiology of Alzheimer's disease. Thioflavin T has been widely used as a fluorescent marker for these amyloid aggregates. Nevertheless, its complex photophysical behavior, with strong wavelength dependencies of all its fluorescence properties, r...

Proton transfer from strong photoacids to hydroxylic solvents is much under debate. Experimentally, the main issue stems from relaxation and diffusion processes that are concomitant with ultrafast proton transfer and blur population dynamics. To overcome this, we propose a fast photodissociation reaction that, however, proceeds slower than solvent...

Strong-acid dissociation was studied in alcohols. Optical excitation of the cationic photoacid N-methyl-6-hydroxyquinolinium triggers proton transfer to solvent, which was probed by spectral reconstruction of picosecond fluorescence traces. The process fulfills the classical Eigen--Weller mechanism in two stages: a) solvent-controlled reversible di...

This paper deals with the interplay between solvent properties and isomerism of 2-(2'-hydroxyphenyl)imidazo[4,5-b]pyridine (1), and the proton and charge-transfer processes that the different isomers undergo in the first-excited singlet state. We demonstrate the strong influence of these processes on the fluorescence properties of 1. We studied the...

The analysis of series of molecular fluorescence or absorption spectra forms an integral part of innumerable investigations on the physicochemical properties of chemical or biological systems. In many typical complex applications, such as photochemical systems with multiple interconversion processes in the ground and in the excited states or bioche...

The ground- and excited-state behaviour of the isomeric species 2-(2'-methoxyphenyl)imidazo[4,5-b]pyridine (1-OMe) and 2-(2'-hydroxyphenyl)-4-methylimidazo[4,5-b]pyridine (1-NMe) in neutral and acid media has been studied by UV-vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy. The new dye 1-NMe is non-fluorescen...

The effect of the aliphatic alcohols methanol, ethanol, propanol, isopropanol, 2-butanol, isobutanol, and tert-butanol on the rate of nitrosation of morpholine at pH 3 and 25 °C has been studied. The inhibition observed is attributed to the formation of alkyl nitrites, which are poor nitrosating agents in acid media. The equilibrium constants for t...

In this paper we report the acid–base behaviour of 2-(n′-pyridyl)benzimidazoles (n′ = 2,3,4) and some methyl derivatives in aqueous solution over a wide range of acidity, involving interesting features with respect to competition in protonation between the benzimidazole N3 and the pyridyl N, with the existence of the corresponding two monocations i...

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The excited-state acid-base behavior of 2-(4′-pyridyl)benzimidazole in aqueous solution has been studied over a wide range of acidity by UV absorption and fluorescence spectroscopy. The species detected in the lowest electronically excited singlet state turned out to be identical to those of the ground state: the anion A, the neutral molecule N, th...

The ground-state rotamerism and tautomerism and the excited-state proton-transfer processes of 2-(1'-hydroxy-2'-naphthyl)benzimidazole (1) and 2-(3'-hydroxy-2'-naphthyl)benzimidazole (2) have been investigated in various solvents by means of UV-vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, and quantum-mechan...

The solvent and temperature dependence of the phototautomerization of 1-methyl-2-(2'-hydroxyphenyl)benzimidazole (4) and the novel compounds 2-(4'-amino-2'-hydroxyphenyl)benzimidazole (1), 2-(4'-N,N-diethylamino-2'-hydroxyphenyl)benzimidazole (2), and 1-methyl-2-(4'-N,N-diethylamino-2'-hydroxyphenyl)benzimidazole (3), together with the ground-state...

Photoinduced proton transfer (PT) from cations 6-hydroxyquinolinium (6HQc) and 6-hydroxy-1-methylquinolinium (6MQc) to water and alcohols, and solvation of the zwitterionic conjugate base 1-methylquinolinium-6-olate (6MQz) were studied with stationary and transient absorption spectroscopy and by quantum chemical calculations. Transient emission spe...

The influence of solvent, temperature, and viscosity on the phototautomerization processes of a series of o-hydroxyarylbenzazoles was studied by means of ultraviolet-visible (UV-vis) absorption spectroscopy and steady-state and time-resolved fluorescence spectroscopy. The compounds studied were 2-(2'-hydroxyphenyl)benzimidazole (HBI), 2-(2'-hydroxy...

Ground-state tautomerism and excited-state proton-transfer processes of 2-(6'-hydroxy-2'-pyridyl)benzimidazolium in H2O and D2O have been studied by means of UV-vis absorption and fluorescence spectroscopy in both steady-state and time-resolved modes. In the ground state, this compound shows a tautomeric equilibrium between the lactim cation, proto...

The ground- and excited-state tautomerism of 2-(6‘-hydroxy-2‘-pyridyl)benzimidazole (1) and 1-methyl-2-(6‘-hydroxy-2‘-pyridyl)benzimidazole (2) in various solvents was investigated by means of UV−vis absorption spectroscopy, steady-state and time-resolved fluorescence spectroscopy, and quantum-mechanical ab initio calculations. A solvent-dependent...

By means of UV absorption and fluorescence spectroscopy, we found that the ground- and excited-state behavior of the monoanion of 2-(6‘-hydroxy-2‘-pyridyl)benzimidazole (1) is solvent dependent. In basified protic solvents (water, ethanol), a tautomeric equilibrium exists in the ground state between the monoanion deprotonated at the hydroxyl group...

The protonated cation of 2-(2‘-hydroxyphenyl)benzimidazole becomes a very strong acid in its first excited singlet state (C*). We studied the proton-transfer process from C* to the bases water, methylurea (MU), and dimethyl sulfoxide (DMSO) in acetonitrile solution by means of fluorescence and UV−vis absorption spectroscopy. We found that the proce...

The ground- and excited-state behavior of the monocations of 2-(6‘-hydroxy-2‘-pyridyl)benzimidazole (1) and 1-methyl-2-(6‘-hydroxy-2‘-pyridyl)benzimidazole (2) is discussed. Excited-state proton transfer from the hydroxyl group to the pyridyl nitrogen occurs in compounds 1 and 2 in acidified acetonitrile solutions by the assistance of an alcohol. W...

The ground- and excited-state behaviour of 1-methyl-2-(3′-hydroxy-2′-pyridyl)benzimidazole (MeHPyBI) in various solvents has been studied by UV–Vis absorption spectroscopy and by time-resolved and steady-state fluorescence spectroscopy. Three species were detected in the ground state in aqueous solutions of pH near to neutrality: a non-planar enol...

Ground-state tautomerism and excited-state proton transfer of 4,5-dimethyl-2-(2‘-hydroxyphenyl)imidazole (DMHI) was investigated by means of UV−vis absorption spectroscopy, by steady-state and time-resolved fluorescence spectroscopy, and by quantum mechanical calculations. The behavior of DMHI in ethanol and water was studied in neutral, acidic, an...

The influence of the solvent on the structure and photoinduced proton-transfer processes of 1-methyl-2- (2′-hydroxyphenyl)benzimidazole (MeHBI) was studied by means of UV–VIS absorption and fluorescence spectroscopy. The steric hindrance of the methyl group determines the non-planar structure of the MeHBI anion and cation in their ground state, but...

The photoinduced proton-transfer processes of 2-(3‘-hydroxy-2‘-pyridyl)benzimidazole in acidic solutions of acetonitrile, ethanol, and water have been studied by means of UV−vis absorption and fluorescence spectroscopy. In all the solvents considered, the ground-state species under acidic conditions is the enol cation, protonated at the benzimidazo...

Excited-state proton transfer in aqueous and ethanolic solutions of 2-(2‘-hydroxyphenyl)benzimidazole (HBI) was investigated by means of UV−vis absorption and fluorescence spectroscopy. The behavior of HBI in water differed from its behavior in ethanol, and in both solvents fluorescence behavior depended on acidity. In both neutral water and neutra...

The excited-state acid-base behavior of 2-(4'-pyridyl)benzimidazole in aqueous solution has been studied over a wide range of acidity by UV absorption and fluorescence spectroscopy. The species detected in the lowest electronically excited singlet state turned out to be identical to those of the ground state: the anion A, the neutral molecule N, th...

In the present work we describe a simple procedure for measuring micelle aggregation numbers of surfactants, which has been designed to introduce students to heterogeneous systems and the techniques by which their physical and chemical properties may be determined. This method is based on the spectroscopic properties of molecules acting as "probes"...

The tautomerism of 2-(3'-hydroxyl-2'-pyridyl)benzimidazole (HPyBI) in the ground and first excited singlet states was investigated by UV-vis absorption spectroscopy, by steady-state and time-resolved fluorescence spectroscopy, and by semiempirical (AM1) calculations (including exploration of the potential energy surface for the interconversion proc...

The fluorescence spectra of 2-(3-pyridyl)benzimidazole (3PBI) and the quaternary salt 2-(1-methyl-4-pyridinio)-benzimidazole iodide (4PBIQS) in aqueous solutions covering a wide range of acidities have been studied to investigate their photophysical behaviour and the acid–base processes occurring in the first excited singlet states of these species...

The photophysical behavior of 2-(2′-pyridyl)benzimidazole (2PBI) in aqueous solution has been studied over a wide range of acidity by UV absorption and steady-state fluorescence spectroscopy and fluorescence decay measurements. Absorption spectra reveal the presence of four different species in the ground state, depending on acidity: the dication (...

The photoexcitation of liquid solutions of 2-(2′-hydroxyphenyl)benzoxazole (HBO) in alkanes leads to a dual phosphorescence which can be assigned to the keto and enol forms of HBO. The keto-enol tautomerism in the metastable triplet state of HBO is practically independent of temperature. The keto and enol bands of the phosphorescence from HBO decay...

The photoexcitation of 2-(2′-hydroxyphenyl)benzoxazole (HBO) in an alkane glass leads to a time-dependent phosphorescence spectrum and multiexponential decay. The complex kinetic behaviour of this phosphorescence results from the site dependence of the energy difference between the keto and the enol form of HBO in the metastable triplet state. All...

From liquid solutions of aromatic hydrocarbons in alkanes three types of delayed luminescence (DL) can be observed: delayed monomer fluorescence, delayed excimer fluorescence and phosphorescence from the aromatic hydrocarbon. According to Lim and co-workers a fourth type of DL (DL4) from solutions of naphthalene and di-α-naphthylalkanes in isooctan...

The purpose of this article is to show that nearly nothing is known on triplet excimers of aromatic compounds in liquid solutions. The article consists of three main parts. (1) The literature on triplet excimer phosphorescence from liquid solutions of phenanthrene, naphthalene and several di-α-naphthylalkanes is critically reviewed. It is shown tha...

Die kinetische Analyse der Nitrosierung von N-Methylanilin im Überschuß durch HNO; bei konstantem pH zeigt, daß am geschwindigkeitsbestimmenden Schritt je eine Aminmolekül sowie ein Nitrit- und Acetation bzw. das aus ihnen als Intermediat entstehende und in sehr geringer Konzentration vorliegende Nitrosylacetat beteiligt sind.

A study of the nitrosation of N-methylaniline and piperazine by nitrous acid in acetate buffer supports a mechanism covering both reactions, whose effective pathway depends on the relationship between the concentrations of nitrite ion, acetate ion, and nitrosatable substrate. In the case of N-methylaniline the only nitrosating agent is nitrosyl ace...

A calculator program for the numerical optimization of physico-chemical parameters by the algorithm of Davies, Swann and Campey is described which includes estimation of the standard deviations of the optimized parameters.

The kinetics of the nitrosation of morpholine in acetate buffer have been studied. It was found that in the experimental conditions used the effective nitrosating agent is dinitrogen trioxide, whose formation is promoted by the acetate ion in accordance with the scheme: No reaction between nitrosyl acetate and the a mine was observed, probably owin...