Search

Abstract: The upwelling events that follow strong trade wind episodes have been described in terms of their remarkable signature in the sea surface temperature southwest off New Caledonia. Upwelling brings deeper, and colder waters to the surface, causing 2–4°C drops in temperature in a few hours, followed by a slower relaxation over several days. Upwelling may sporadically bring nutrients to the surface under certain conditions, and increase the biological productivity. Two multidisciplinary hydrographic cruises allow the impact of upwelling on the chemical and biological properties of the water to be documented. Both cruises took place in austral summer (December 2004 and December 2005), but the first cruise occurred during a strong upwelling event, while the second cruise occurred in calm conditions. The water properties and planktonic composition show important contrasts, with a strong southeastward current (the “ALIS current of New Caledonia”) competing with the upwelling system. Our analysis suggests that, while observed productivities are far less than those of typical upwelling systems, some wind events in New Caledonia may contribute to biological activity. A currentmeter mooring, deployed during the second cruise, documents the ocean response to a changing wind field and the local impact of upwelling on currents and temperatures on the water column. The results are discussed, with the help of climatology, Argo float profiler data, satellite data and of a high-resolution numerical simulation. [ABSTRACT FROM AUTHOR]

Abstract: This article describes the partial hydrolysis of the multidentate ligand 2,4,6-tris(pyrazol-1-yl)-1,3,5-triazine in the presence of copper(II), to give the anionic ligand 2,4-dione-1,3,5-(1H)-triazin-1-amido, which was isolated as the cupric complex catena-[CuL(H2O)Cl] n , where L is the amido ligand. No other hydrolysis products were isolated or identified. The complex defines a zigzag 1D covalent chain, along the b cell axis, through apical copper–oxygen bonds (Cu–N–C–O···Cu bridges). [Copyright &y& Elsevier]

Abstract: Three compounds based on the polyoxometalate building block [V12B18O60H6], (Na)10[(H2O)V12B18O60H6]·18H2O (1), Na8[Cu(en)2]2[V12B18O60H6](NO3)2·14.7H2O (2), Na7[Cu(en)2]2[V12B18O60H6](NO3)·15.5H2O (3), (en=ethylenediamine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction analysis and TGA. Compound 1 consists of polyoxovanadium borate [V12B18O60H6] clusters which are surrounded by sodium countercations in octahedral sites, stabilized by electrostatic interactions with the oxygen atoms of both vanadium and boron centres. However, compounds 2 and 3 correspond to more complicated structures, constructed from the same polyoxometalate clusters, which are interconnected by [Cu(en)2]2+ moieties via the terminal oxygen atoms of the polyoxoanions, generating one-dimensional structures. The functionalization of this polyoxovanadium borate cluster has been obtained by the use of [Cu(en)2]2+ complex ions, thus demonstrating the capacity of the terminal oxygen atoms of the cluster to bind transition metal centres. The structural stability of the [V12B18O60H6] cluster permits the formation of functionalized polyoxometalate clusters, generating various crystalline lattices. [Copyright &y& Elsevier]

Abstract: The synthesis and molecular structures of three new copper (II) complexes with the ligand 2,6-bis-[N-(2-pyridylethyl)-formidoyl]-4-methyl phenol (L–OH) are reported. The complexes were prepared by reaction of L–OH with CuX2 · nH2O, affording [Cu2(L–O)(μ-OH)(μ-ClO4)](ClO4) (I); , with KOH in the reaction media; or [Cu2(L–O)(μ-Cl)2][Cu2Cl6]0.5 (II); X=Cl, in neutral conditions. The presence of methyl 3,4-dihydroxy-benzoate (CAT-(OH)2) during the synthesis of I leads to the complex [Cu2(L–O)(μ-OH)(CH3OH)][Cu(CAT-O2)2]0.5(ClO4) (III). This compound exhibits an uncommon anion consisting of a bis-(catecholate) cuprate (II) moiety. The complete series of complexes show bridging phenoxo groups between the copper centers, together with hydroxo and perchlorate bridges found in I or two chlorides found in II. Compound I exhibit a rather low catalytic activity for the oxidation of 3,5-ditertbutyl catechol under aerobic conditions (12% quinone formation after 48h at room temperature, in methanol solution 1×10−3 M in catalyst and 1×10−2 M in catechol), which could be ascribed to steric limitations of the catechol to coordinate the central Cu2O2 core. [Copyright &y& Elsevier]

The title compound corresponds to a molecular product of the hydrothermal reaction of CuCl2, Zn, and BIPY (BIPY=2,2′-bipyridine) in the presence of phosphoric acid. The structure of the neutral complex Cu4(μ2-Cl)4(BIPY)2 determined by means of X-ray diffraction consists of molecular units constructed around a Cu4 parallelogram, with diagonally opposed tetrahedral and linear copper centers. DFT calculations provide a rationalization of the bonding in this molecule. [Copyright &y& Elsevier]

• Three crystal structures are reported for tetracarbonyl-tungsten complexes. • π-π and M−CO (lone pair)⋯π(aryl) interactions and stabilize the crystal packing. • Substituents in the phen ligand decrease (OC) eq –W–(CO) eq angle. • (OC) eq –W–(CO) eq angle affects the absorption features. • High-energy emission band is favored with smaller (OC) eq –W–(CO) eq angle. • Emission lifetime for the low-energy emission band decreases with smaller (OC) eq –W–(CO) eq angle. In this work, methyl and phenyl substituents were introduced in the 2,9- and 4,7-positions of the phen ligand in order to study its impact on the structural and photophysical properties of [W(CO) 4 (phen-type)] complexes [phen-type = 4,7-dimethyl-1,10-phenanthroline (4,7-DMPhen); 4,7-diphenyl-1,10-phenanthroline (BPhen), and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)]. Crystallographic analysis of these complexes allows to investigate the correlation between the geometrical parameters with their photophysical properties measured by steady-state and time-resolved spectroscopies. The (OC) eq –W–(CO) eq angle is the most significantly influenced geometrical parameter by the substituents, showing values of 92.5°, 90.2°, and 81.2° for [W(CO) 4 (4,7-DMPhen)] , [W(CO) 4 (BPhen)] , and [W(CO) 4 (BCP)] , respectively. The smallest angle observed for [W(CO) 4 (BCP)] is attributed to a steric repulsion exerted by the methyl groups to the equatorial carbonyls. Remarkably, a smaller OC eq –W–CO eq angle favors the High-Energy (HE) emission band, as evidenced in the photoluminescence (PL) spectra of [W(CO) 4 (BCP)]. Conversely, a greater angle favors the Low-Energy (LE) emission band, as observed in the PL spectra of [W(CO) 4 (4,7-DMPhen)] and [W(CO) 4 (BPhen)]. The PL lifetime of the LE emission band becomes shorter when decreasing the (OC) eq –W–(CO) eq angle. Furthermore, the absorption feature was affected by the 2,9-dimethyl substituents, showing greater contribution from the high-energy shoulder on the visible absorption band. This study shows that the perturbation of the (OC) eq –W–(CO) eq angle induced by the substituents in the phen ligand influences on the photophysical properties of [W(CO) 4 (phen-type)] complexes. [ABSTRACT FROM AUTHOR]

Lercanidipine (LERCA) is a third generation antihypertensive drug belonging to the 1,4-dihydropyridine’s family, which has been reported to induce photoallergic and/or phototoxic effects in patients with long term treatment. The electronic nature of substituents on the 4-aryl moiety bonded to the 1,4-dihydropyridine ring has been described to strongly affect the photophysical and photochemical behavior of this family of compounds, which displays a typical absorption band around 360 nm. LERCA undergoes photodegradation after excitation, with a first order kinetic, in significant competition to the radiative path. The photodegradation quantum yields for LERCA are higher than for its homologue nimodipine (NIMO), thus indicating that the substituents on the 1,4-dihydropyridinic ring also affect their photophysical and photochemical properties. The media where the photodegradation takes place impacts on the product profile, in a homogeneous one the photoproducts obtained appear to be more polar than those obtained for a micro-heterogeneous one (micelles or bilayers mimicking biological media). [ABSTRACT FROM AUTHOR]

Soluble proteins were extracted from common wheat flour obtained from nine cultivars of different qualities and were analyzed by nanoUPLC and Ultra Definition Mass Spectrometry (UDMS E ) label-free quantitative approach. Collectively, 5894 proteins were identified and quantified with 8 peptides/protein. A total of 414 proteins were found differentially expressed with 85% proteins not yet described in the literature, according to their biological function. Quality-related proteins, such as puroindolines and chaperones, notably involved in the gluten-protein folding process, were up-regulated in superior (SP) and medium (MD) flours qualities and down-regulated in the low (LW) ones. Domains related to the chaperones activity were also found up-regulated in SP and MD and down-regulated in LW. In this work, nanoUPLC-UDMS E analysis was effective to identify and quantify metabolic proteins, allowing a clear distinction of the wheat flours and providing new perspectives for evaluating the technological quality based on the low abundant proteins of wheat endosperm. [ABSTRACT FROM AUTHOR]

The reaction of [ P,N -{(C 6 H 5 ) 2 (C 5 H 4 N)P}Re(CO) 3 Br] ( RePNBr ) with silver triflate leads to the complex [ P,N -{(C 6 H 5 ) 2 (C 5 H 4 N)P}Re(CO) 3 ( O -CF 3 SO 3 )] ( RePNTfO ) with moderate yield. This new P,N -Re I triflate compound contains the anion directly coordinated to the metal, completing an octahedral environment. RePNTfO displays in dichloromethane (DCM) solution an irreversible oxidation about +1.35 V and three irreversible reduction processes at −1.38 V, −2.03 V and −2.30 V. Oxidation has been attributed to the Re I /Re II couple, while the reduction corresponds to PN -ligand processes, which is consistent with those computed by means of DFT. The absorption spectrum of RePNTfO in DCM displays a maximum at 295 nm ( ε = 7.1 × 10 3 M −1 cm −1 ) and a shoulder around 350 nm ( ε = 1.8 × 10 3 M −1 cm −1 ), which have been assigned to intraligand (π → π ∗ ) and metal to ligand charge transfer (MLCT, dπ → π ∗ ) transitions with the help of DFT/TDDFT. Excitation of RePNTfO in DCM at 350 nm leads to an emission spectrum centered at 535 nm. The analysis of the variation of the absorption and emission spectra in coordinating solvents compared to non-coordinating DCM, DFT/TDDFT calculations modeling and ELF analysis suggests for coordinating solvents that triflate ligand is replaced in the coordination sphere of Re I in solution. Kinetics of the exchange of triflate by bromide measured in DCM at different temperatures allowed to estimate the Eyring parameters: Δ H ≠ , Δ S ≠ and Δ G ≠ , 50.8 kJ mol −1 , −109.6 J K −1 mol −1 and 83.5 kJ mol −1 respectively. The high negative entropy is indicative of a compact transition state, compatible with an associative mechanism, I a , for the exchange. [ABSTRACT FROM AUTHOR]

[(pypyr)Re(CO) 3 Br] has a moderate emission quantum yields while [(pypyr-anthra)Re(CO) 3 Br] and [Br(CO) 3 Re(pypyr-anthra-pypyr)Re(CO) 3 Br] are very weak ones but these two last molecules showed a remarkably high yield for molecular oxygen sensitization. [Display omitted] The ligand 2-(1H -pyrazol-1-yl)pyrazine (pypyr) was prepared by reaction of 2-bromopyrazine with N -lithium pyrazolate with 92.5% yield, while the anthracenyl derivatives 2-(anthracen-9-yl)-5-(1 H -pyrazol-1-yl)pyrazine (pypyr-anthra) and 9,10-bis(5-(1 H -pyrazol-1-yl)pyrazin-2-yl)anthracene (pypyr-anthra-pypyr) were prepared by reaction of the 9-anthraceneboronic or bis-boronic acid pinacol ester with 2-bromo-5-(1 H -pyrazol-1-yl)pyrazine with medium yields (49.6 and 31.5 % respectively). The respective ReI(CO) 3 Br complexes: [(pypyr)Re(CO) 3 Br] , [(pypyr-anthra)Re(CO) 3 Br] and [Br(CO) 3 Re(pypyr-anthra-pypyr)Re(CO) 3 Br] were prepared in high yields (94, 84 and 78 % respectively) by reaction with bromotricarbonyl(tetrahydrofuran)rhenium(I) dimer. DFT modelling suggests the anthracenyl moiety is not coplanar with the pyrazolyl-pyrazine fragment, defining a dihedral angle of 65° and 67° for [(pypyr-anthra)Re(CO) 3 Br] and [Br(CO) 3 Re(pypyr-anthra-pypyr)Re(CO) 3 Br] respectively. Each one of the three rhenium(I) molecules shows a quasi-reversible reduction wave around − 1.10 V, assigned by comparison with the uncoordinated ligand, the pypyr fragment, while additional reductions waves related to this core or the anthryl arms are present. UV–Vis spectra show absorption bands and/or shoulders around 400–450 nm for the series of compounds in solution. The respective extinction coefficients (∼4 × 103 M−1cm−1), the sensitivity to solvent polarity and DFT modelling suggest they corresponds to MLCT Re dπ → π (pyr) * transitions. Despite their high emissivity, the uncoordinated ligands completely lose their emission upon coordinated to ReI(CO) 3 Br. The rhenium(I) complexes emit around 650 nm upon excitation, although [(pypyr)Re(CO) 3 Br] is a moderate emissive molecule, while [(pypyr-anthra)Re(CO) 3 Br] and [Br(CO) 3 Re(pypyr-anthra-pypyr)Re(CO) 3 Br] are very weak ones. In contrast these two last molecules showed a remarkably high yield as singlet oxygen sensitizers. [ABSTRACT FROM AUTHOR]

The [(phen)Re(CO) 3 (OOCCH 3)] and [(bppdz)Re(CO) 3 (OOCCH 3)] acetates prepared from the corresponding bromides are dual emitters. [Display omitted] The reaction of the 3,5-dimethylpyrazolyl-pyridazine-6-carboxylic acid (Me 2 LCOOH) or pyrazolyl-pyridazine-6-carboxylic acid (LCOOH) with [(THF)(CO) 3 Re(µ-Br) 2 Re(CO) 3 (THF)] in DMF followed by the addition of traces of water leads to a series of dehalided rhenium(I) tricarbonyl carboxylates: [(Me 2 LCOO)(H 2 O)Re(CO) 3 ] and [(LCOO)(H 2 O)Re(CO) 3 ] instead of the normal rhenium(I) tricarbonyl bromide obtained by reaction in chloroform, [(Me 2 LCOOH)Re(CO) 3 Br]. The reaction is believed to occur through adventitious amine in the reaction media which leads to the carboxylic acid deprotonation and reaction. To test this idea the diimine-rhenium(I) tricarbonyl bromide [(phen)Re(CO) 3 Br] and [(bppdz)Re(CO) 3 Br] ( phen : 1,10-phenanthroline; bppdz : 3,6-bis(1 H -pyrazol-1-yl)pyridazine) were reacted with glacial acetic acid and triethylamine in dry DMF at room temperature. These reaction lead to the corresponding rhenium(I) acetates [(phen)Re(CO) 3 (OOCCH 3)] and [(bppdz)Re(CO) 3 (OOCCH 3)] in good to high yields using soft reaction conditions and without the use of a silver salt. Thiethylammonium bromide is also obtained from the reaction. Moreover, the fact that this unexpected rhenium(I) tricarbonyl carboxylates were obtained in as N,N and N,O coordination isomers for [(Me 2 LCOO)(H 2 O)Re(CO) 3 ] and the comparison of the newly synthetized [(phen)Re(CO) 3 (OOCCH 3)] and [(bppdz)Re(CO) 3 (OOCCH 3)] compounds with their corresponding bromides allow to stablish that the replacement of the halide by a carboxylate hypsochromically shift the energy of the MLCT band while the emission experiences the opposite, it is bathochromically shifted. The emission quantum yields are slightly diminished. Interestingly the [(phen)Re(CO) 3 (OOCCH 3)] and [(bppdz)Re(CO) 3 (OOCCH 3)] acetates are dual emitters. [ABSTRACT FROM AUTHOR]

The spectroscopic, electrochemical and photophysical properties of the new complex [ P,N -{(C 6 H 5 ) 2 (C 5 H 4 N)NHP}Re(CO) 3 Br] ( RePNN ) are reported. The UV–Vis spectrum in dichloromethane (DCM) shows an absorption maximum centered at 300 nm and a shoulder at 350 nm. These absorption bands have been characterized, having a π py → π ∗ py and a MLCT character. Excitation at the first wavelength (higher energy) leads to an emission band centered at 365 nm. Cyclic voltammetry shows a fully irreversible oxidation wave around +1.45 V, assigned to Re I /Re II couple, whereas two irreversible reduction signals centered at −0.75 and −1.20 V are assigned to ligand reduction processes. The photophysical results show that emission from the RePNN complex comes exclusively from the ligand. The MLCT excited state shows to be non-emissive by coupling to vibrational modes leading to non-radiative decay path to ground state. The luminescent decay fits to a bi-exponential function. DFT calculations suggest that intra-ligand π py → π ∗ py and π py → π ∗ ph excited states may account for the existence of these two decay lifetimes. The additional –NH– fragment present in the 2-(diphenylphosphinoamino)pyridine ligand compared to 2-pyridylphosphine, makes it more flexible and in consequence, enhances the non-radiative decay rate constant from the 3 MLCT to the ground state in the RePNN complex compared to those of 2-pyridylphosphine, [ P,N -{(C 6 H 5 ) 2 (C 5 H 4 N)PRe(CO) 3 Br] ( RePN ). [ABSTRACT FROM AUTHOR]

The multimetallic complex [[(CO) 3 ( phen )Re(μ-Br)Re( phen )(CO) 3 ][(CO) 3 Re(μ-Br) 3 Re(CO) 3 ]]·CH 2 Cl 2 was prepared by direct reaction of (Re(CO) 3 (THF)Br) 2 (THF: tetrahydrofuran) and 1,10-phenanthroline in a 1:1 ratio, followed by recrystallization in dichloromethane. The compound is an ionic salt where both, cation and anion, are bimetallic complexes. Inside both of them the Re I centers are bridged by one or three bromides respectively. The compound has an absorption band centered at 375 nm in CH 2 Cl 2 , which has been assigned to a MLCT band. Excitation at 375 nm produces luminescent emission at 608 nm. Comparison of these results with closely related rhenium complexes, in addition to Time Dependant-DFT analysis, allow us to propose the [(CO) 3 ( phen )Re(μ-Br)Re( phen )(CO) 3 ] + cation as main responsible for luminescence. Luminescence lifetime and singlet oxygen formation quantum yield suggest also that the emissive excited state has a triplet character. [ABSTRACT FROM AUTHOR]

• The synthesized Ru(II) complexes reported high conversions in imines hydrogen using the hydrogen transfer reaction as hydrogen source. • The synthesized Ru(II) complexes achieved high conversions in hydrogen transfer reaction to acetophenone. • The electronic, structural, and steric properties of the ligands influence catalytic performance of the synthesized complexes. This work describes the synthesis and characterization of Ru(II) compounds with general formula cis-Cl- cis-P cis-N- RuCl 2 (PN) 2 (where PN represents a heterobidentate PN-donor chelated ligand) and their application as catalysts in the reduction of acetophenone and imines hydrogenation via hydrogen transfer reaction using 2-propanol as the hydrogen source. Single crystal diffraction analysis for all synthesized ruthenium complexes shows non-regular octahedral coordination around the metal. All the synthesized Ru(II) complexes achieved high conversions and turnover frequencies in hydrogen transfer reaction to acetophenone (830 h−1) and imine hydrogenation (760 h−1 for N-benzylideneaniline). The complex (dichloro bis-(8-(diphenylphosphino)quinoline)ruthenium(II)) (RuL2) achieved high conversion in imine hydrogenation, while the complex(dichloro bis-(N-(diphenylphosphino)pyridin-2-amine)ruthenium(II)) (RuL3) showed high conversion in acetophenone reduction. It was found that the electronic, structural, and steric properties of the ligands could influence catalytic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: EPR measurements have been performed on single crystals of [Cu(L‐tyrosine)2]∞ at 33.8GHz and at room temperature. The EPR spectra display partially resolved EPR lines for most orientations of the magnetic field in the ab plane, and only one resonance for orientations close to the crystal axes, while only a single line is observed along any direction in the ca and cb crystal planes. This behavior is a result of the selective collapse of the resonances corresponding to the four copper sites in the unit cell produced by the exchange interactions between the copper ions. The magnitudes of the exchange interactions between the copper ions were evaluated from the angular variation of the line width and the collapse of the EPR lines. The value |J AD/k B |=0.8K between neighboring copper atoms at 4.942Å is assigned to a syn−anti equatorial−apical carboxylate bridge with a total bond length of 6.822Å, while the small value |J AB/k B |=0.004K is assigned to a long bridge of 11 atoms with a total bond length of 19.186Å, that includes one resonance assisted hydrogen bond (RAHB). This finding is discussed in terms of values obtained for similar paths in other model compounds and in proteins. [Copyright &y& Elsevier]

The spectroscopic properties and tautomeric behavior of five novel Rhenium (I) tricarbonyl complexes bearing an azo ligand are presented. The organic ligand is stable in solution as the hydrazone tautomer. It remains as hydrazone in different medium conditions (solvent, concentration, pH, etc.) without the formation of detectable amounts of the azo tautomer. However, the complexation of this ligand to the strong electron-withdrawing fragment -Re(CO) 3 X (X = Cl−, Br−) causes tautomerism to appear in the organic moiety. Two well-defined regions in the electronic spectra for both tautomers were observed, allowing the azo/enol-keto/hydrazone equilibrium to be followed. TD-DFT calculations indicate that for the keto/hydrazone form, the main absorption band is attributed to an IL transition. In contrast, the azo/enol species shows a major contribution of the 1MLCT (dπ(Re) → dπ*(NN)) transition. The tautomeric equilibrium is easily shifted using solvents with different dielectric constant and hydrogen bond donor/acceptor (HBD/HBA) abilities. Also, the tautomerization process is deeply influenced by the electronic properties of the axial ligand. Therefore, this behavior represents a different strategy for the design of novel materials with optical properties. Furthermore, tautomerism is affected by the concentration of complexes and the presence of water in solvents. The acid-base behavior of these compounds in a 50% v/v ethanol-buffer system showed that the azo/enol tautomer is stabilized in acidic media. At the same time, an increase of pH promotes tautomerization toward the keto/hydrazone, followed by forming the anionic form at pH > 8. [Display omitted] • Novel Re(I) complexes bearing an azo/hydrazone ligand were obtained. • Tautomerism of the hydrazone ligand is triggered by the -Re(CO) 3 L core. • The axial ligand and experimental conditions modulate the tautomeric equilibrium. • Main electronic transitions for both tautomers were dilucidated by TD-DFT. [ABSTRACT FROM AUTHOR]

The reaction of 2,2'-bipyrimidine (bpm) with [Re(CO) 3 (THF)Br] 2 or [Re(CO) 5 Br] leads to a pure or a mixture of [(bpm)Re(CO) 3 Br] and anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br]. Adding a Re(CO) 3 Br center to [(bpm)Re(CO) 3 Br] decreases the HOMO-LUMO gap, red-shifts the absorption and quenches the emission. [Display omitted] The reaction of [Re(CO) 3 (THF)Br] 2 and 2,2′-bipyrimidine (bpm) in dichloromethane at room temperature employing a stoichiometric 2:1 ratio leads to a mixture of [(bpm)Re(CO) 3 Br] (21%) and anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br] (79%). When a 1:1 ratio is used, only anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br] is obtained in a 89% yield. The reaction of [Re(CO) 5 Br] and (bpm) leads to [(bpm)Re(CO) 3 Br ] as a single product. [(bpm)Re(CO) 3 Br] and anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br] display one and two rhenium(I) centers of distorted octahedral coordination geometry respectively, each with a facial ligand correlation. The intramolecular metal to metal distance is 5.8508(16) Å in anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br]. The HOMO-LUMO gap for [(bpm)Re(CO) 3 Br] results 0.74 eV larger (3.03 vs 2.29 eV) than the computed for anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br]. In the same sense, the anti-isomer is computed to be 0.14 eV (13.4 kJ mol−1) more stable compared to the hypothetical syn -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br]. Cyclic voltammetry shows that the difference between the ReI/Re0 reduction and its ReI/ReII oxidation in terms of potential is about 3.46 V for [(bpm)Re(CO) 3 Br ], while this value diminishes to 2.62 V for anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br]. Following this tendency, the MLCT band for [(bpm)Re(CO) 3 Br] is centered at 385 nm (DMF), while it is red-shifted almost 100 nm for anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br]. While [(bpm)Re(CO) 3 Br ] emits at 680 nm (excited at 380 nm), anti -[Br(CO) 3 Re( μ-bpm)Re(CO) 3 Br] remains non-emissive, which is attributed to a favored vibrational deactivation path. [ABSTRACT FROM AUTHOR]

The reactivities of [trans-R2MoO(NNPhR′)(o-phen)], R=R′=Me (1); R=Me, R′=Ph (2); R=Ph, R′=Me (3); R=R′=Ph (4), toward (i) neutral 1,1-disubstituted hydrazines, R′PhNNH2 and (ii) 1,1-disubstituted hydrazine hydrochlorides, R′PhNNH2·HCl, R′=Me, Ph, were studied in acetonitrile. In the first case, no condensation reaction of the free oxo group was observed under different experimental conditions. In the second case, using a 1:1 precursor/hydrazine hydrochloride molar ratio, the oxo group was also unreactive, instead one methyl or phenyl group bonded to molybdenum was displaced as methane or benzene and was subsequently substituted by one chloride ligand affording complexes formulated as [trans-RClMoO(NNPhR′)(o-phen)], R=R′=Me (5); R=Me, R′=Ph (6); R=Ph, R′=Me, (7)·MeCN; R=R′=Ph, (8)·MeCN. Finally, when a 1:2 precursor/hydrazine hydrochloride molar ratio was used, both methyl and phenyl groups were substituted affording complexes formulated as [trans-Cl2MoO(NNPhR′)(o-phen)], R′=Me (9), R=Ph (10). The new organometallic compounds were characterised by IR, UV–Vis and 1H NMR spectroscopy while the crystal and molecular structure of 6 was determined by X-ray diffraction analysis. [Copyright &y& Elsevier]

Herein, a study is presented, addressed to understand the influence of the terbium (III) species contained in a thermoplastic polyurethane (TPU) matrix. The studied terbium (III) species were terbium (III) nitrate, Tb(NO 3) 3 ·5H 2 O, and a terbium (III) complex, [TbL (NO 3) 2 ](NO 3) (H 2 O), where L is a macrocyclic ligand derived from 2,6-pyridinedicarboxyaldehyde and ethylenediamine. SEM-EDXS showed that in both films the terbium (III) species were homogeneously distributed in the polymer matrix. The film doped with the nitrate salt displayed different physical properties, in comparison to the pristine TPU and the film containing the terbium (III) complex. Both TPU/TbIII films, exhibiting a green color emission, with a G/B ratio being temperature independent. By comparison of the emission of both films containing terbium (III) species, the TPU/TbIII complex film presented a more intense luminescence due to the antenna effect. TPU doped with the nitrate salt showed weak emission, indicating the lack of sensitizing groups. [Display omitted] • TPU Hydrogen bonding disrupted, and crystalline phase decreased by the presence of TbIII ions. • TPU cold crystallization induced by the presence of TbIII ions. • Interactions of TbIII with TPU moieties inhibited by the presence of polydentate macrocyclic ligand. [ABSTRACT FROM AUTHOR]

We synthesize and characterize the luminescent tricarbonyl rhenium complex, [(bpy)(H 2 O)Re(CO) 3 ]+, and propose a reasonably simple preparation of an aptamer-functionalized lipid core micelle (LCM) loaded with this complex. The carrier was functionalized in situ with the nucleolin aptamer, AS1411, to improve the complex delivery and uptake to target cells. • Luminescent tricarbonyl rhenium complex. • Aptamer functionalized carrier. • Solid lipid nanoparticles. • Cellular uptake. Due to its distinctive physicochemical properties, diimine rhenium(I) tricarbonyl complexes are one of the most common type of complexes used in cellular imaging. The reasonably simple synthesis and modification of rhenium complexes in addition to their stability and remarkable luminescent properties provide a robust method to perform this goal. In general, organometallic complexes must be biocompatible to development imaging agents. Consequently, modification and bio-functionalization of the transition complexes is crucial to enhance biocompatibility. Here, we synthesize and characterize the luminescent tricarbonyl rhenium complex, [(bpy)(H 2 O)Re(CO) 3 ]+, and propose a reasonably simple preparation of an aptamer-functionalized lipid core micelle (LCM), loaded with this complex, to endow it with suitable properties to be used in cellular imaging. The [(bpy)(H 2 O)Re(CO) 3 ]+ exhibit a broad emission band centered around 550 nm at room temperature after excitation at 360 nm. The luminescent intensity is higher in nonpolar solvents such as chloroform. The complex was loaded into LCMs and, at the same time, the carrier was functionalized in situ with the nucleolin aptamer, AS1411, to improve the complex delivery and uptake to target cells. After physicochemical and spectroscopic characterization of the aptamer-functionalized vehicle, cellular studies were performed to evaluate its toxicity and its efficiency as cellular imaging agent. The combined AS1411 aptamer-functionalized lipid core micelle system effectively encapsulated the [(bpy)(H 2 O)Re(CO) 3 ]+ complex, maintained its luminescent properties, and showed potential features to be used in cellular imaging experiments. [ABSTRACT FROM AUTHOR]

In the present work, we synthesized and characterized two complexes: fac -Re(CO) 3 (4,5-diazafluoren-9-one)Br (ReL1) and fac -Re(CO) 3 (5,6-epoxy-5,6-dihydro-1,10-phenanthroline)Br (ReL2), where ReL2 has not been reported at present. In this study, we show a complete structural characterization of both ReL1 and ReL2 by elemental analysis, FTIR, 1H and 13C NMR, DEPT, and HHCOSY. Moreover, we carried out UV–Vis and luminescence experiments in organic solvents showing different polarities. In addition, we performed relativistic theoretical calculations to better understand electronic transitions and optical properties. We also assessed the cytotoxicity of ReL1 , ReL2 , and their respective N,N ligands (i.e., 4,5-diazafluoren-9-one and 5,6-epoxy-5,6-dihydro-1,10-phenanthroline) against walled-cells, including Gram-negative bacteria (Salmonella enterica serovar Typhimurium), non-sporulated Gram-positive bacteria (Staphylococcus aureus), sporulated Gram-positive bacteria (Bacillus cereus), and yeasts (Candida albicans and Cryptococcus spp.). We observed that these complexes exhibited very low or no cytotoxicity. We also found that only ReL2 , and not ReL1 , exhibited good properties as a luminescent probe for this kind of cells. Accordingly, we found that ReL2 showed good potential to be directly used as a luminescent probe for walled cells, including yeasts (e.g., Candida albicans) and bacteria (e.g. , Salmonella enterica), which can be observed by confocal microscopy. Image 1 • Rhenium (I) complexes can be used as staining probes for non-walled cells. • Less is known regarding their use for walled cells (yeasts and bacteria). • In this study, we synthesized and characterized ReL1 and ReL2. • ReL2 exhibited good photophysical features as fluorophore. • ReL2 was useful to stain yeasts and bacteria for confocal microscopy. [ABSTRACT FROM AUTHOR]

Organometallic imines containing 4- and 5-nitrothiophene were prepared and characterized by conventional spectroscopy and X-ray crystallography. The EC 50 values obtained against T. b. brucei and T. cruzi indicate that 5-nitrothiophene derivatives were more active than 4-nitrothiophene analogues. These results agree with E 1/2NO2 values and with NO 2 group Mulliken charges calculated. • Cyrhetrenyl and ferrocenyl imines containing isomeric nitrothienyl moieties were synthetized. • The molecular structure of organometallic compounds (1a , 2a , and 3a) was determined by single-crystal XRD. • The anti-parasitic activities of all complexes were investigated. • Theoretical studies about the nitro group position correlate with the anti-parasitic activity. This study compares the nitro group position of thienyl imines bound to organometallic fragments, and the respective electrochemical and anti-parasitic properties. Ferrocenyl and cyrhetrenyl imines derived from 4-nitrothiophene (1a - 3a) and 5-nitrothiophene (1b - 3b) were synthesized and characterized by spectroscopic techniques. In addition, molecular structure of 1a , 2a and 3a were determined by X-ray crystallography. The reduction potential of the nitro group (E 1/2), determined by cyclic voltammetry, shows that imines with a 5-nitrothiophene moiety exhibit lower E 1/2 values (E 1/2 = −0.56 to −0.78 V) than 4-nitro derivatives (E 1/2 = −0.92 to −1.04 V), indicating that 5-nitro compounds better generate radical species. The 5-nitrothiophene derivatives (1b - 3b) were more active against T. b. brucei (trypomastigotes) and T. cruzi (epimastigotes) than 4-nitrothiophene analogues (1a - 3a). Enhanced trypanocidal properties in 5-nitrothiophenes may be due to NO 2 group reduction being readily converted to their downstream, trypanocidal products. Based on the anti-parasitic activity and Selectivity Index determined for all derivatives, 1b emerged as an appropriated agent for treatment of trypanosomal infections. Additionally, evaluations of T. b. brucei susceptibility showed that compound 3b is a substrate for TbNTR1. Density Functional Theory (DFT) calculations were used as an approximation to rationalize the influence of nitro group positions on the heterocyclic ring regarding electrochemical behaviour and anti-parasitic activity. [ABSTRACT FROM AUTHOR]

The UV–Vis absorption spectrum of the rhenium(I) tricarbonyl complex [(NH 2 - phen)Re(CO) 3 Br] (ReNN-NH 2 Br , a deep-orange solid) in solution shows three bands located at 300, 370 and 445 nm. TD-DFT calculations and spectroscopic data indicate that the higher energy band corresponds to a ligand centered transition (LC), while the two lower energy bands have been ascribed to have major ILCT and MLCT character. Excitation at 370 nm leads to two emission bands centered at around 490 nm and 590 nm, which have different nature, 1ILCT and 3MLCT, respectively. Both show a low luminescent quantum yield, especially the lowest energy band. The emission quantum yields in argon-saturated solutions are largely increased, specially for the band at 590 nm. Our results demonstrate that adding the amino group has a non-innocent effect over the luminescent properties of the complex when is compared with those of [(phen)Re(CO) 3 Br] (ReNNBr). The capacity of these complexes to act as singlet oxygen sensitizers and their application as oxygen sensors were explored. Both complexes, ReNNBr and ReNN-NH 2 Br , were incorporated in silsesquioxane matrices and tested as ratiometric oxygen sensors using the intrinsic emission of the matrix as an emission internal reference signal. The SSO1-ReNN-NH 2 Br films was the most sensitive material for this application. • Amino linker group modulates photophysical properties of rhenium tricarbonyl complex. • Participation of MLCT and ILCT excited states described by theoretical approach. • Rhenium complex in silsesquioxane matrix exhibits oxygen sensing linear response. • Intrinsic emission of matrices can be used as an emission internal reference signal. [ABSTRACT FROM AUTHOR]

The photophysics of three polymorphs of the rhenium(I) dimer [(CO) 3 (phen)Re(μ-OH)(phen)Re(CO) 3 ]+Br− with different values of Re–O–Re bridging angle is analyzed, both in solution and solid state, relating in this way the observed luminescence to the structure. The reaction of [ReIBr(CO) 3 (THF)] 2 with phenanthroline in solution leads to the diimine rhenium(I)tricarbonyl [(phen)Re(CO) 3 Br] and the dimer [(CO) 3 (phen)Re(µ-OH)(phen)Re(CO) 3 ]+Br− (1+ Br−) as a by-product (~5% yield). This latter bimetallic compound crystallizes as a mixture of three polymorphs, with variable amount of solvent: 1+ Br−·CHCl 3 (triclinic and orthorhombic) and 1+ Br−·2(CHCl 3) (triclinic). Rietveld analysis showed 38, 54 and 8% of 1+ Br−·CHCl 3 (triclinic), 1+ Br−·CHCl 3 (orthorhombic) and 1+ Br−·2(CHCl 3) (triclinic) respectively. The 1+ cation shows two [ReI(phen)(CO) 3 ]+ units connected by means of a central hydroxyl group. Noteworthy, the bridging Re–O–Re angle varies between 130.9(7)° to 140.7(2)° along the polymorphic series. UV–Vis spectrum for the 1+ shows a broad absorption band around 390 nm in CH 2 Cl 2 which has been attributed to has MLCT character (Re(d π) → π*(phen)) as confirmed by DFT. Excitation at 405 nm in solution leads to emission at 595 nm (DCM), 605 nm (DMF) and 625 nm (CH 3 CN). The emission follows a mono-exponential law of decay and has lifetime of 405.8 ns (DCM). The solid-state polymorphic mixture absorbs around 460 nm. Excitation of the solid at 320 nm leads to emission with a maximum at 575 nm, which follow a bi-exponential law of decay with two components, a short one τ 1 of 27.0 ns and longer one τ 2 of 178.5 ns. These results suggest that the emitting state does not vary as function of the molecular geometry. [ABSTRACT FROM AUTHOR]