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Featured researches published by Ema Horak.


New Journal of Chemistry | 2017

Fluorescent benzimidazo[1,2-a]quinolines: synthesis, spectroscopic and computational studies of protonation equilibria and metal ion sensitivity

Marijana Hranjec; Ema Horak; Darko Babić; Sanela Plavljanin; Zrinka Srdović; Ivana Murković Steinberg; Robert Vianello; Nataša Perin

We describe the UV-Vis and fluorescence spectroscopic characterization of newly synthesised amino and diamino substituted benzimidazo[1,2-a]quinolines and their various 1 : 1 metal complexes together with the related computational analysis of their acid/base properties and metal binding affinities. The work was performed in order to evaluate the photophysical features of these compounds and assess their potential chemosensor activity towards pH and metal ions in several polar and non-polar organic solvents. In addition, pH titrations and titration with metal chloride salts were carried out to determine the selectivity towards Co2+, Cu2+, Ni2+ and Zn2+ cations and explore their potential as chemosensors and pH probes. While all systems exhibit notable but impractical differences in sensitivities and spectral responses with the used metals, computational analysis aided in identifying benzimidazo[1,2-a]quinolines mono- and disubstituted with the piperazine fragment as very promising and efficient pH sensors in the acidic environment, particularly in the range of pH ≈ 3, which is extended to pH ≈ 6 upon the addition of metal cations. Their analytical features are significantly better than those involving the chain amino substituents, and their further development is strongly suggested.


Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2017

Benzimidazole acrylonitriles as multifunctional push-pull chromophores: Spectral characterisation, protonation equilibria and nanoaggregation in aqueous solutions

Ema Horak; Robert Vianello; Marijana Hranjec; Svjetlana Krištafor; Grace Karminski Zamola; Ivana Murković Steinberg

Heterocyclic donor-π-acceptor molecular systems based on an N,N-dimethylamino phenylacrylonitrile benzimidazole skeleton have been characterised and are proposed for potential use in sensing applications. The benzimidazole moiety introduces a broad spectrum of useful multifunctional properties to the system including electron accepting ability, pH sensitivity and compatibility with biomolecules. The photophysical characterisation of the prototropic forms of these chromophores has been carried out in both solution and on immobilisation in polymer films. The experimental results are further supported by computational determination of pKa values. It is noticed that compound 3 forms nanoaggregates in aqueous solutions with aggregation-induced emission (AIE) at 600nm. All the systems demonstrate spectral pH sensitivity in acidic media which shifts towards near-neutral values upon immobilisation in polymer films or upon aggregation in an aqueous environment (compound 3). The structure-property relationships of these functional chromophores, involving their spectral characteristics, acid-base equilibria, pKa values and aggregation effects have been determined. Potential applications of the molecules as pH and biomolecular sensors are proposed based on their pH sensitivity and AIE properties.


Supramolecular Chemistry | 2018

Colourimetric and fluorimetric metal ion chemosensor based on a benzimidazole functionalised Schiff base

Ema Horak; Robert Vianello; Marijana Hranjec; Ivana Murković Steinberg

Abstract Herein we present the interaction of benzimidazole based Schiff base 1 with different metal ions studied by absorption and fluorescence spectroscopies and computational modelling. Compound 1 exhibits changes in spectroscopic properties upon chelation with specific metal ions. Its strong absorption band at 425 nm is significantly red shifted (Δλ = 30 nm) only upon the complexation with Al3+, an effect observable by a naked eye as a colour change from light- to dark-yellow. Of the metal ions investigated, only Al3+ caused any increase in the fluorescence intensity of 1. All other metal ions, including K(I), Na(I), Ag(I), Li(I), Zn(II), Co(II) and Hg(II), showed a negligible fluorescence response, while Cu(II) and Fe(III) significantly decreased the fluorescence intensity. Therefore, system 1 is a promising colourimetric sensor for Al3+, and a fluorescence sensor for Cu2+ and Fe3+ ions. Computational analysis revealed that 1 is unionized in ethanol solution, while it becomes di-deprotonated to 1 2– upon the complexation with Al3+. This changes the electronic structure of 1 and leaves no acidic hydrogen atoms to allow the ESIPT process. On the other hand, the presence of monovalent metal cations induces only mono-deprotonation to 1 – , which turns out to be an insufficient electronic change to be spotted in the recorded spectra.


Supramolecular Chemistry | 2018

Benzimidazole as a structural unit in fluorescent chemical sensors: the hidden properties of a multifunctional heterocyclic scaffold

Ema Horak; Petar Kassal; Ivana Murković Steinberg

Abstract Benzimidazole (BI) derivatives are structurally similar to naturally occurring nucleotides, a fact that enables their use as scaffolds in biologically active organic synthetic compounds. However, BI can serve as a multifunctional unit in heteroaromatic molecular systems for optoelectronics and non-linear optics, photovoltaics, and in sensing and bioimaging. Its many structure-related properties such as electron accepting ability, π-bridging, chromogenic pH sensitivity/switching and metal-ion chelating properties, also make BI an exceptional structural candidate for optical chemical sensors. The design of novel benzimidazole-based chemosensors is a challenging task. In this review, molecular sensing systems based on intramolecular charge transfer, photoinduced electron transfer and excited-state intramolecular proton transfer mechanisms are systematically examined and the role of the benzimidazole unit is discussed. Novel and emerging developments such as sensors based on aggregation-induced emission phenomena are also included. Conclusions are made on the advantages and disadvantages of existing fluorophores and chemosensors and guidelines are given for further design and development of new sensing systems based on benzimidazole.


Dyes and Pigments | 2012

Synthesis, crystal structure and spectroscopic study of novel benzimidazoles and benzimidazo[1,2-a]quinolines as potential chemosensors for different cations

Marijana Hranjec; Ema Horak; Martina Tireli; Gordana Pavlović; Grace Karminski-Zamola


Dyes and Pigments | 2017

Reversible pH switchable aggregation-induced emission of self-assembled benzimidazole-based acrylonitrile dye in aqueous solution

Ema Horak; Marijana Hranjec; Robert Vianello; Ivana Murković Steinberg


Sensors and Actuators B-chemical | 2018

Benzimidazole functionalised Schiff bases: Novel pH sensitive fluorescence turn-on chromoionophores for ion-selective optodes

Ema Horak; Petar Kassal; Marijana Hranjec; Ivana Murković Steinberg


Reviews in Analytical Chemistry | 2017

Wireless and Mobile Optical Chemical Sensors and Biosensors

Petar Kassal; Ema Horak; Marija Sigurnjak; Matthew D. Steinberg; Ivana Murković Steinberg


Sensors and Actuators B-chemical | 2018

Wireless fluorimeter for mobile and low cost chemical sensing: A paper based chloride assay

Petar Kassal; Matthew D. Steinberg; Ema Horak; Ivana Murković Steinberg


EUROPT(R)ODE XIV Naples 2018, XIV Conference on optical chemical sensors and biosensors, March 25-28, Naples, Italy | 2018

Optical sensing properties of novel click- derived 1, 2, 3-triazoles and bis-triazolyl- appended benzenes

Kristina Bobanović; Ema Horak; Lidija Furač; Ivana Murković Steinberg; Svjetlana Krištafor

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