Search

We studied the reactivity of HS− with a family of zinc complexes. The different fluorescence trends observed for 1 and 3 in the presence of HS− has been related with the possible existence of non-radiative decay paths, by means of a DFT-analysis.

In this work, we investigate the mode of interaction of a family of fluorescent zinc complexes with HS- and H2S. Different experiments, performed by diverse spectroscopic techniques, provide evidence that HS- binds the zinc center of all the complexes under investigation. Treatment with neutral H2S exhibits a markedly different reactivity which indicates selectivity for HS- over H2S of the systems under investigation. Striking color changes, visible to the naked eye, occur when treating the systems with HS- or by an H2S flow. Accordingly, also the fluorescence is modulated by the presence of HS-, with the possible formation of multiple adducts. The results highlight the potential of the devised systems to be implemented as HS-/H2S colorimetric and fluorescent sensors. Bioimaging experiments indicate the potential of using this class of compounds as probes for the detection of H2S in living cells.

In this work we explore the interaction of HS− with a family of fluorescent zinc complexes. In particular we selected a family of complexes with N,O-bidentate ligands aiming at assessing whether the zinc-chelating ligand plays a role in influencing the reactivity of HS− with the complexes under investigation. Different experiments, performed by diverse spectroscopic techniques, provide evidence that HS− binds the zinc center of all the complexes included in this study. The results highlight the potential of the devised systems to be used as HS−/H2S fluorescent sensors via a coordinative-based approach. To shed light on the species formed in solution when HS−/H2S interacts with the title complexes and aiming to rationalize the photophysical properties of the sensing constructs, we performed a computational analysis based on the time dependent density functional theory (TD-DFT). Preliminary bio-imaging experiments were also performed and the results indicate the potential of this class of compounds as probes for the detection of H2S in living cells.

This review highlights the recent developments in the field of metalloporphyrins as optical probes for biologically relevant molecules, such as nitric oxide (NO) and hydrogen sulfide (H2S), and as catalysts for the preparation of sustainable polymers such as polyesters, by the ring-opening polymerization (ROP) of cyclic esters and the ring-opening co-polymerization (ROCOP) of epoxides and anhydrides, and polycarbonates by the chemical fixation of carbon dioxide (CO2). The great potential of porphyrins is mainly due to the possibility of making various synthetic modifications to the porphyrin ring, such as modifying the coordinated metal, peripheral substituents, or even the molecular skeleton. Due to the strict structure–property relationships, one can use porphyrinoids in several different applications such as, for instance, activation of molecular oxygen or catalysis of photosynthetic processes. These possibilities broaden the application of porphyrins in several different fields of research, further mimicking what nature does. In this context, here, we want to provide evidence for the great flexibility of metalloporphyrins by presenting an overview of results obtained by us and others in the research fields we are currently involved in. More specifically, we report a survey of our most significant achievements regarding their use as optical probes in the context of the results reported in the literature from other research groups, and of the use of porphyrin metal(III) complexes as catalysts for sustainable polymerization processes. As for the optical probe section, in addition to the metalloporphyrins synthesized ad hoc in the laboratory, the present work also covers the natural proteins containing a porphyrin core.

The aim of the present review is to highlight the most recent achievements in different fields of application of salen-based zinc and aluminum complexes. More specifically this article focuses on the use of aluminum and zinc salen-type complexes as optical probes for biologically relevant molecules, as catalysts for the ring opening polymerization (ROP) of cyclic esters and co-polymerization of epoxides and anhydrides (ROCOP) and in the chemical fixation of carbon dioxide (CO2). The intention is to provide an overview of the most recent results from our group within the framework of the state-of-art-results in the literature.

In this work, we investigate the mode of interaction of a family of fluorescent zinc complexes with HS– and H2S. Different experiments, performed by diverse spectroscopic techniques, provide evidence that HS– binds the zinc center of all the complexes under investigation. Treatment with neutral H2S exhibits a markedly different reactivity which indicates selectivity for HS– over H2S of the systems under investigation. Striking color changes, visible to the naked eye, occur when treating the systems with HS– or by an H2S flow. Accordingly, also the fluorescence is modulated by the presence of HS–, with the possible formation of multiple adducts. The results highlight the potential of the devised systems to be implemented as HS–/H2S colorimetric and fluorescent sensors. Bioimaging experiments indicate the potential of using this class of compounds as probes for the detection of H2S in living cells., In this work, we studied the reactivity of HS− with a family of fluorescent zinc complexes via a variety of spectroscopic techniques. Interaction with HS− results in its coordination to the Zn center for all the complexes under investigation. Treatment with neutral H2S exhibits a markedly different reactivity which indicates selectivity for HS− over H2S. Striking color changes, visible to the naked eye, occurred when treating the systems with HS− or by an H2S flow.

A pentadentate cage-like cyclam-based fluorescent ligand has been designed, synthesized and characterized by monodimensional and bidimensional NMR analysis. To further characterize the title ligand ESI-MS, Uv-vis and fluorescence experiments have been also performed. Its suitability as a chemosensor for the detection of Cu2+ ions has been successfully explored via a variety of spectroscopic techniques (i.e. ESI-MS, Uv-vis and fluorescence). The Job's plot experiment together with the ESI-MS experiments indicate a 1:1 stoichiometry for the binding of Cu2+ to the cyclam-based ligand. Fluorescence experiments corroborate this hypothesis. The system resulted selective in the recognition of copper and stable for a week, as assessed via fluorescence spectroscopy. The Cu(II) complex has been isolated and tested as a fluorescent probe for the detection of H2S. NMR and ESI-MS investigation provided evidence that H2S recognition occurs via a copper displacement mechanism, as reported in the literature for different copper complexes. The system functions with a selective response to HS- harnessing a concentration-dependent 'turn-on' of the initial fluorescence intensity.

Binding of hydrogen sulfide (H2S) to a zinc porphyrin complex and the stabilization of the related zinc hydrosulfido adduct are explored. High-resolution MALDI Fourier transform ion cyclotron resonance mass spectrometry (HR MALDI-FT-ICR) and 1H NMR experiments provide evidence that HS− coordination occurs at the zinc centre. The coordination of HS− occurs in a reversible manner and modulates fluorescence emission of a tetra(N-methylpyridyl)porphine zinc complex (TMPyPZn). The results highlight the potential of TMPyPZn and related systems for the implementation of fast and simple H2S sensors via a coordinative-based approach.

WOS:000458689800019; International audience; Hydrogen sulfide (H2S) is an important biological messenger, which recently joined nitric oxide (NO) and carbon monoxide (CO) as an endogenously produced gasotransmitter. This discovery resulted in a renewed interest towards H2S and, in particular, in its reactivity with biological and bioinorganic targets. However, in the scientific literature studies exploring the reactivity of H2S/HS- with non-heme proteins are rare. In this work, we studied the interaction of HS- with the natural metalloprotein Cu-azurin and its cobalt variant via UV-Vis, fluorescence, and EPR spectroscopy, as well as X-ray diffraction. Interaction of HS- significantly enhances the fluorescence emission of fluorescently labelled copper azurin in buffered solutions and at physiological pH. In contrast, fluorescently labelled cobalt azurin undergoes a fluorescence quenching in the presence of HS- in line with the changes observed in the absorption spectrum of the construct. The results highlight the potential of azurin for implementation in a fast and simple HS- sensor.

In the present work, we explored the reactivity of HS− with a family of fluorescent metal complexes via a variety of spectroscopic techniques. The complexes under investigation are obtained by complexation of zinc or nickel with pyridoxal-based ligands. More specifically complexes 1 and 2 are zinc complexes namely L1Zn(II) and L2Zn(II) where L1 stands for N,N′-phenylenebis(pyridoxyliminato) and L2 is N,N′-binaphthylenebis(pyridoxyliminato), whereas complex 3 is a nickel complex (L3Ni(II)) where L3 is N,N′-ethylenebis(pyridoxyliminato). A combination of NMR, ESI-MS, UV–vis and fluorescence experiments provide evidence that HS− binds the metal center in the case of complexes 1 and 3 whereas for complex 2, ZnS precipitation and hydrolysis of the organic ligand occur. Fluorescence experiments indicate that in the presence of HS− complex 1 undergoes a consistent fluorescence enhancement whereas for complex 3 the parent fluorescence exhibits a visible quenching. The results highlight the potential of complex 1 to be implemented as a HS− fluorescent sensor via a coordinative-based approach.

H2S and its conjugate base HS- have recently gained increasing attention for their reactivity with bioinorganic targets. However, so far, stable adducts of bioinorganic compounds with H2S/HS- are still scarce due to the propensity of sulfide to form insoluble metal sulfides. In this work, we studied the reactivity of HS- with a family of fluorescent zinc complexes via a variety of spectroscopic techniques. The complexes selected for this study feature a pyridoxal moiety with different substituent groups on the ligand framework. Interaction of the complexes under investigation with HS- results in the displacement of the coordinated ligand from the Zn center with the concomitant precipitation of ZnS in the case of complexes 1 and 3, whereas for complex 2 our data points to the coordination of HS- to the metal center likely assisted by hydrogen bonding with the OH of the pyridoxal moiety. In the presence of HS-, the fluorescence emission of complex 2 is enhanced, whereas the fluorescence emission of complexes 1 and 3 is quenched. The results highlight the potential of complex 2 to be implemented as a HS- fluorescent sensor via a coordinative-based approach.

A “turn on” fluorescence-based probe for sensing H2S in water via a coordinative-based approach has been successfully devised. The probe can selectively detect H2S in aqueous solutions over other anions, biothiols, and common oxidants such as H2O2. 1H NMR spectroscopy and ESI-MS experiments provide evidence that the turn-on response in the presence of H2S is due to binding of the target anion to the copper center.

H 2 S is an important biological messenger but its reactivity and physiological concentrations are largely controversial. On the other hand, reactivity of H 2 S with biologically relevant metal scaffolds for the selective tracking of H 2 S in biological fluids is underexplored. In this work we investigated interaction of monohydrogensulfide with a series of zinc porphyrins by 1 H NMR, UV–vis and ESI mass experiments. The results provide evidence that HS − binds the metal center for all the investigated complexes.

Vanadium compounds can exert anticancer effects, partly due to inhibition of tyrosine phosphatases. Here, we report the effect of N,N'-ethylenebis (pyridoxylideneiminato) vanadium (IV) complex (Pyr2 enV(IV)), that induced 93% and 57% of cell mortality in A375 (human melanoma) and A549 (human lung carcinoma) cells, respectively; the mortality was

The last decades have seen a marked escalation in interest in the biology of naturally occurring gases. Examples of the most significant of these gases are nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S). All of them feature a number of physiological and/or pathophysiological functions within the human body. For example, NO regulates vasodilatation in the circulatory system and long-term potentiation in the brain. CO modulates vasorelaxation, vascular smooth muscle cell growth and tissue injury. H2S relaxes vascular smooth muscle and inhibits smooth muscle cell proliferation. In addition, it acts as neuromodulator in the central nervous system. Furthermore, it is also well acknowledged that all of them are differently associated with various human diseases. However, for the advancement of our understanding of the physiological and pathological roles played by these signal transductors, there is a pressing need for methods allowing their detection in both aqueous and gaseous media. The aim of this review is to highlight the recent developments in the field of metal complexes as fluorescent probes for the detection of gasotransmitters and to provide a general overview of fluorescent sensors implemented so far for NO, CO and H2S.

The DNA molecule, recognized as the carrier of genetic information in vivo, can function as an efficient organocatalyst for Michael additions of 1,3-dicarbonyl compounds to activated alkenes in aqueous media. The procedure described here is environmentally benign and offers several advantages in terms of simplicity, generality and efficiency. We have used fluorescence spectroscopy to evaluate the catalytic activity of a molecule of DNA.

In this work we present an innovative optical sensing methodology based on the use of biomolecules as molecular gating nano-systems. Here, as an example, we report on the detection of analytes related to climate change. In particular, we focused our attention on the detection of nitric oxide (NO) and oxygen (O2). Our methodology builds on the possibility of modulating the excitation intensity of a fluorescent probe used as a transducer and a sensor molecule whose absorption is strongly affected by the binding of an analyte of interest used as a filter. The two simple conditions that have to be fulfilled for the method to work are: (a) the absorption spectrum of the sensor placed inside the cuvette, and acting as the recognition element for the analyte of interest, should strongly change upon the binding of the analyte and (b) the fluorescence dye transducer should exhibit an excitation band which overlaps with one or more absorption bands of the sensor. The absorption band of the sensor affected by the binding of the specific analyte should overlap with the excitation band of the transducer. The high sensitivity of fluorescence detection combined with the use of proteins as highly selective sensors makes this method a powerful basis for the development of a new generation of analytical assays. Proof-of-principle results showing that cytochrome c peroxidase (CcP) for NO detection and myoglobin (Mb) for O2 detection can be successfully used by exploiting our new methodology are reported. The proposed technology can be easily expanded to the determination of different target analytes.

New zinc complexes (LOMe)ZnCl(2) (1) and (LOH)ZnCl(2)(2) of the heteroscorpionate ligands 1-[(3,5-di-tert-butyl-2-methoxyphenyl)(3,5-dimethyl-pyrazol-1-yl)methyl)]-3,5-dimethyl-pyrazole (LOMe) and 2,4-di-tert-butyl-6-[bis(3,5-dimethyl-pyrazol-1-yl)methyl]phenol (LOH) have been synthesized. The X-ray molecular structure of 2 was reported and compared with the one of the iron(II) complex (LOH)FeI(2) (3). The complexes 2-3 adopt a tetrahedral structure in the solid state in which the LOH ligand is kappa(2)-coordinated to the metal via the imino nitrogens of the two pyrazolyl rings. The hydroxyl phenyl group is not coordinated to the metal but found to be involved in an intermolecular hydrogen bond. The solution structures of 1 and 2 are consistent with this tetrahedral C(S) symmetric geometry. Dilution and (1)H-(1)H Nuclear Overhauser Effect Spectroscopy (NOESY) experiments revealed that the free ligands LOMe and LOH are involved in intra- and intermolecular hydrogen bonding interactions. Coordination of LOMe and LOH to ZnCl(2) was investigated by NMR titration methods. Association constants (K(a)) of (8.6 +/- 0.4) x 10(2) M(-1) and (7.8 +/- 0.3) x 10(2) M(-1) were obtained in methanol/water solutions (95:5) for LOMe and LOH, respectively. Coordination of bis(3,5-dimethyl-pyrazol-1-yl)methane (bpm) ligand to ZnCl(2) is weaker, as evidenced by the lower value of the association constant (5.3 +/- 0.3) x 10(2) M(-1). When bpm was added to solutions of 1 or 2, an equilibrium shifted toward the (bmp)ZnCl(2) species was observed. The thermodynamic parameters for this reaction were determined by VT NMR analysis. The optical properties of the ligands (LOMe, LOH) and of the corresponding zinc complexes 1 and 2 were also investigated by means of UV-vis and fluorescence spectroscopy to assess the potential use of these ligands as fluorescent sensors for Zn(2+) detection.

Fluorescently labeled type-3 copper proteins have been proposed previously as solution oxygen sensors by using a FRET mechanism. Herein, we describe how this principle can be adapted to sense O 2 by means of proteins immobilized in optically transparent silica matrices. Specifically, the protein, hemocyanin from Octopus vulgaris N-terminally labeled with Cy5, is immobilized in two different kinds of optically transparent silica matrices, which appear to be a promising platform for enzyme encapsulation. The presented results provide proof of principle that fluorescently labeled proteins immobilized in a silica matrix can be implemented in a reusable, biocompatible and stable oxygen measuring device that might lead to new developments in the field of optical biosensing.

Two enantiomers of a chiral binaphthyl-bridged salen dichlorozirconium (IV) complex (namely R-A-1 and S-A-1) were synthesized and tested as pre-catalysts for 4-methyl-1-hexene (4MH) polymerization. Their behavior was compared with that of the same complex in its racemic form. Isotactic poly(4-methyl-1-hexene) was produced in both cases, but the polymerization of racemic 4MH promoted by the optically active catalysts preferentially consumed one antipode, showing some stereoselectivity for the process.

The reaction of alkylcobaloxime [Co(dmgH)2(CH2CH3)(py)] (1) (dmgH = the anion of dimethyl-glyoxime) with KSH in water solution resulted in the selective displacement of the pyridine axial ligand affording the derivative K[Co(dmgH)2(CH2CH3)(SH)] (2). An 1H–1H EXSY experiment revealed that the substitution is reversible and occurs in a slow exchange regime. Attempts to grow crystals of the HS− adduct led to isolation of a rare example of the unexpected trisulfido-bridged dinuclear complex K2[Co2(dmgH)2(CH2CH3)2(μ-S3)]. It was shown that the glyoximato ligands provided the metal centre with a coordination environment quite robust to prevent decomposition and constitute a suitable platform for developing the chemistry of organometallic complexes bearing hydrogensulfido or oligosulfido ligands.

New fluorinated bis(phenoxyaldimine)- and bis(phenoxyketimine)titanium(IV) complexes bearing o-halide substituents on the phenolate rings were synthesized and tested as catalysts for propene polyme...

Two diiminobis(phenolate) zirconium complexes [C6H10-{NCH-(3,5-tBu2C6H2-2-O)-κO}2]ZrX2 [X = CH2Ph (1), Cl (3)] have been synthesized and characterized by NMR solution spectroscopy. Complex 1 was found conformationally stable and isolated in the octahedral C2 symmetric form. When exposed to the light in hydrocarbon solution, 1 readily undergoes to 1,2 benzyl migration converting the diiminobis(phenolate) ligand in the corresponding benzylamidoiminobis(phenolate). Complex 3 is more thermally stable and found in slow equilibrium between the cis-α and cis-β forms with the former largely prevalent (9:1 molar ratio). The rate of interconversion between the two diastereoisomers was estimated in 3.6 × 10-1 s-1 by NMR exchange spectroscopy (EXSY). 1 and 3 are active ethylene polymerization catalysts after reaction with MAO or [CPh3][B(C6F5)4]/Al-iBu3. The polydispersity index of polyethylene produced by 1 is about 2, suggesting the presence of a single active species and that the symmetry of the precatalyst is ret...

Water-soluble iron and manganese pyridoxal-based complexes pyr2enFeCl (1) and pyr2enMnCl (2) (pyr2en = N,N'-ethylenebis(pyridoxylideneiminato) have been synthesized and characterized. Proof-of-principle results that the title complexes can be efficiently used as fluorescent probes for nitrite and nitrate detection are provided. The fluorescent complex pyr2enFeCl (1) selectively recognizes nitrate anions by fluorescent enhancement in an aqueous solution displaying high binding affinities. ESI-MS experiments clearly show the binding of these anions via the substitution of the chloride anion at the metal center. The pyridoxal-based manganese complexes of NO2(-) and NO3(-) have been isolated, and their structures have been established by single-crystal XRD. Density functional theory (DFT) calculations show that the substitution of the chloride anion at the metal center by the nitrite or nitrate anion is favored by the gain in the energies of hydration.

In this paper, the use of tyrosinase (Ty) from Streptomyces antibioticus, labeled with a fluorescent tag, in combination with soluble quinoprotein (PQQ-containing) glucose dehydrogenase (s-GDH) to measure trace amounts of phenols is explored. Proof of concept is provided by a series of experiments, which show a clear quantitative dependence of the response on the phenol concentration. One of the advantages of the detection system is that apart from a standard fluorimeter no further instrumentation is required.

We report on the successful use of a new zinc complex for the selective fluorescent detection of ADP and ATP in water. This is achieved by the complementary coordination of the phosphate groups to the metal centre and hydrogen bonding of the adenosine with the coordinated ligand.

Fluorescently labeled cobalt peptide deformylase (Co-PDF) can be efficiently used as a fluorescence-resonance-energy-transfer-based sensing device for hydrogen sulfide (H(2)S). The proof of concept of our sensor system is substantiated by spectroscopic, structural, and theoretical results. Monohydrogen sulfide coordination to Co-PDF and Ni-PDF was verified by X-ray crystallography. Density functional theory calculations were performed to gain insight into the characteristics of the coordination adduct between H(2)S and the cobalt cofactor in Co-PDF.

Vanadium compounds can exert anticancer effects, partly due to inhibition of tyrosine phosphatases. Here, we report the effect of N,N'-ethylenebis (pyridoxylideneiminato) vanadium (IV) complex (Pyr2 enV(IV)), that induced 93% and 57% of cell mortality in A375 (human melanoma) and A549 (human lung carcinoma) cells, respectively; the mortality was24% in other cancer cell lines and in human normal epidermal keratinocytes, lung cells and peripheral blood mononuclear cells. The mechanism of Pyr2 enV(IV) effect relied on apoptosis induction; this was triggered by ROS increase, followed by mitochondrial membrane depolarization. Indeed, the addition of N-acetyl cysteine to cell cultures abated Pyr2 enV(IV)-induced apoptosis. These results disclose the pro-apoptotic activity of Pyr2 enV(IV) and its mechanism, relying on intracellular ROS increase.

The field of optical sensors has been a growing research area over the last three decades. A wide range of books and review articles has been published by experts in the field who have highlighted the advantages of optical sensing over other transduction methods. Fluorescence is by far the method most often applied and comes in a variety of schemes. Nowadays, one of the most common approaches in the field of optical biosensors is to combine the high sensitivity of fluorescence detection in combination with the high selectivity provided by ligand-binding proteins. In this chapter we deal with reviewing our recent results on the implementation of fluorescence-based sensors for monitoring environmentally hazardous gas molecules (e.g. nitric oxide, hydrogen sulfide). Reflectivity-based sensors, fluorescence correlation spectroscopy-based (FCS) systems, and sensors relying on the enhanced fluorescence emission on silver island films (SIFs) coupled to the total internal reflection fluorescence mode (TIRF) for the detection of gliadin and other prolamines considered toxic for celiac patients are also discussed herein.

Ephedrine is a crucial chemical precursor for clandestinely produced amphetamine and its related drugs. Also, ephedrine is intentionally added to illegal preparations of methamphetamine or amphetamine because it is cheaper than the other two drugs. Consequently there is a pressing need to prevent the entry of ephedrine into commerce. Therefore the challenge calls for non-invasive techniques that provide data on the presence of ephedrine even in trace amounts. In this paper we describe the synthesis of a new ephedrine derivative with a carbon linker featuring an amino reactive group, and its conjugation to the glutamine binding protein (GlnBP) from E. coli as a carrier protein for the production of polyclonal antibodies against ephedrine. Proof-of-principle results of an efficient SPR-based indirect competitive immunoassay for the detection and quantification of ephedrine are presented. The detection limit of the assay was about 33 ng ml−1.

The field of optical sensors has been a growing research area over the last three decades. A wide range of books and review articles has been published by experts in the field who have highlighted the advantages of optical sensing over other transduction methods. Fluorescence is by far the method most often applied and comes in a variety of schemes. Nowadays, one of the most common approaches in the field of optical biosensors is to combine the high sensitivity of fluorescence detection in combination with the high selectivity provided by ligand-binding proteins. In this chapter we deal with reviewing our recent results on the implementation of fluorescence-based sensors for monitoring environmentally hazardous gas molecules (e.g. nitric oxide, hydrogen sulfide). Reflectivity-based sensors, fluorescence correlation spectroscopy-based (FCS) systems, and sensors relying on the enhanced fluorescence emission on silver island films (SIFs) coupled to the total internal reflection fluorescence mode (TIRF) for the detection of gliadin and other prolamines considered toxic for celiac patients are also discussed herein.

The Saccaromices cerevisiae D-serine dehydratase is a pyridoxal 5'-phosphate dependent enzyme that requires zinc for its function. It catalyses the conversion of D-serine into pyruvate and ammonia with the K(m) and k(cat) values of 0.39 mM and 13.1 s(-1) respectively. In this work, a new methodology for monitoring D-serine is presented. Our results show that this enzyme could be successfully used as a biological probe for detection of D-serine via fluorescence spectroscopy.

A series of platinum(II) complexes supported by the tridentate bis(phosphine)phosphido ligand bis(2-diisopropylphosphinophenyl)phosphide) [(i)Pr-PPP] have been synthesized and characterized (1-4). X-Ray structural studies of [(i)Pr-PPP]PtCl (1) and [(i)Pr-PPP]PtCH(3) (3) complexes show meridional [(i)Pr-PPP] ligands around approximately square-planar platinum centers. Structural data and NMR analysis highlight a strong trans influence for the phosphido phosphorous donor, comparable to that of the anionic aryl carbon of the classic PCP pincer complexes. A series of thermally stable [PPP]Pt(IV) compounds, including [PPP]Pt(CH(3))(2)X [X = I (5) and SbF(6) (6)], were also synthesized. The study of the binding affinity of SO(2) and NO to complex 1 has also been addressed.

The coordination behavior and reactivity of the phenol-substituted bis(pyrazolyl)methane ligands, (3,5-(t)Bu(2)-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L1-H) and 2-phenol-bis(3,5-Me(2)-pyrazol-1-yl)methane (L2-H) have been investigated in the metal complexes (L1-H)CoCl(2) (1), (L1-H)ZnCl(2) (2), (L3)CuCl(2) (3), (L2)(2)Co(2)Cl(2) (4) (L2-H)ZnCl(2) (5), and (L2-H)CuCl(2)·H(2)O (6). The mononuclear tetrahedral cobalt complex 1 was isolated and fully characterized by X-ray single crystal diffraction and (1)H NMR spectroscopy and relaxometry. The neutral L1-H is κ(2)-coordinated to the metal center whereas the not coordinated hydroxy-phenyl group is involved in extended intermolecular hydrogen bonds. Aerobic oxidation of L1-H was observed in the reaction of this ligand with CuCl(2) to yield the para-quinone derivative L3 (L3 = 2-(t)Bu-6-(bis(3,5-Me(2)-pyrazol-1-yl)methyl)cyclohexa-2,5-diene-1,4-dione). Upon oxidation L3 resulted κ(2)-coordinated to the tetrahedral Cu(II) metal center, affording 3. The reaction of L2-H with CoCl(2)·6H(2)O produced the elimination of 1 equiv of hydrochloric acid and the formation of the binuclear complex 4 in which one cobalt is in an octahedral environment featuring two κ(3)-coordinated deprotonated ligands whereas the second cobalt center is detected in tetrahedral coordination geometry, bound to the octahedral cobalt via two phenoxo bridging moieties. Interestingly L2-H, (3-(t)Bu-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L4-H), or (5-(t)Bu-2-phenol)bis(3,5-Me(2)-pyrazol-1-yl)methane (L5-H) were not oxidized in the reaction with CuCl(2). The reaction of the ligand L2-H with ZnCl(2) and CuCl(2)·2H(2)O yielded the κ(2)-coordinated tetrahedral complex 5 and the square planar complex 6, respectively. The application of the cobalt complex 1 as molecular dosimeter for H(2)S was explored and compared to that of the zinc analogue 2. Density functional theory (DFT) calculations and NMR experiments to assess the possible mechanisms of H(2)S detection by both 1 and 2 are also described.

A new, fast, simple and cost-effective sensing device for monitoring H(2)S has been developed. Proof-of-principle results showing that a commercial and cheap Myoglobin (Mb) can be successfully used as a biological probe for a fluorescence biosensor for H(2)S detection are reported. The two different commercial labels Cy3 and Atto620 were selected for this study. A high selectivity for detecting H(2)S against other thiols was found. The applicability of the proposed sensing system was successfully explored not only in solution but also when applied in the form of a solid state device.

In this paper we explore the use of fluorescently labeled cytochrome c peroxidase (CcP) from baker's yeast for monitoring nitric oxide (NO) down to the sub-micromolar level, by means of a FRET (Forster Resonance Energy Transfer) mechanism. The binding affinity constant ( K d ) for the NO binding to CcP was determined to be 10 ± 1.5 µM. The rate of NO dissociation from the CcP ( k off ) and the second order rate constant for the NO association ( k on ) were found to be 0.22 ± 0.08 min − 1 and 0.024 ± 0.002 µM − 1 min − 1 respectively. The immobilization of fluorescently labeled CcP into a polymeric matrix for use in a solid state NO sensing device was also explored. The results provide proof-of-principle that labeled CcP can be successfully implemented in a fast, simple, quantitative and sensitive NO sensing device.

Fluorescently labeled hemocyanin has been previously proposed as an oxygen sensor. In this study, we explored the efficacy of this biosensor for monitoring the biological oxygen consumption of bacteria and its use in testing bacterial cell growth and viability of Escherichia coli, Pseudomonas aeruginosa, Paracoccus denitrificans, and Staphylococcus simulans. Using a microwell plate, the time courses for the complete deoxygenation of samples with different initial concentrations of cells were obtained and the doubling times were extracted. The applicability of our fluorescence-based cell growth assay as an antibacterial drug screening method was also explored. The results provide a proof-of-principle for a simple, quantitative, and sensitive method for high-throughput monitoring of prokaryotic cell growth and antibiotic susceptibility screening.

A new Salan zirconium complex is synthesized and tested as a precatalyst for the polymerization of ethylene and higher α-olefins. Its catalytic behavior is compared to that of a previously reported and related Salen zirconium complex. Analysis of the produced polyolefins reveals that the two different catalytic systems produce polymers with the same microstructure: atactic polymers from propene versus highly isotactic polymers from higher α-olefins. The identification of the end groups indicates a prevailing primary regiochemistry of polyinsertion of the α-olefins for both Salan and Salen zirconium complexes. These observations strongly suggest the formation of very similar active species in both systems.

Three new binaphthyl-bridged Schiff base complexes featuring different phenolate substituents (meta-Me, ortho,para-di-Cl, ortho,para-di-Br) were synthesized. 1H and 13C NMR analyses indicated that the cis-β isomers are preferentially formed in any case. These complexes were tested as precatalysts for ethylene and propene polymerization comparing their behaviour to that of related titanium and zirconium complexes previously reported. The beneficial effect on polymerization activity of halogen atoms in the ortho, para positions of the phenolate rings was also demonstrated.