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In this work, we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study demonstrated that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could largely hinder the reaction rate, whereas toluene (aprotic apolar) did not. In both cases, product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data and allowed for the proposal of a model based on substrate–solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide to benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion) due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, thereby widening its use.

Fish fraud is a problematic issue for the industry. For it to be properly addressed will require the use of accurate, rapid, and cost-effective tools. In this work, near infrared reflectance spectroscopy (NIRS) was used to predict nutritional values (protein, lipids, and moisture) as well as to discriminate between sources (farmed vs. wild fish) and conditions (fresh or defrosted fish). Samples of five whitefish species—Alaskan pollock (Gadus chalcogrammu), Atlantic cod (G. morhua), European plaice (Pleuronectes platessa), common sole (Solea solea), and turbot (Psetta maxima)—including farmed, wild, fresh, and frozen ones, were scanned by a low-cost handheld near infrared reflectance spectrometer with a spectral range between 900 and 1700 nm. Several machine learning algorithms were explored for both regression and classification tasks, achieving precisions and coefficients of determination higher than 88% and 0.78, respectively. Principal component analysis (PCA) was used to cluster samples according to classes where good linear discriminations were denoted. Loadings from PCA revealed bands at 1150, 1200, and 1400 nm as the most discriminative spectral regions regarding classification of both source and condition, suggesting the absorbance of OH, CH, CH2, and CH3 groups as the most important ones. This study shows the use of NIRS and both linear and non-linear learners as a suitable strategy to address fish fraud and fish QC.

The biobased polyester poly(ethylene 2,4-furanoate) (2,4-PEF) is a potentially interesting yet insufficiently studied polymer whose resistance to crystallization fundamentally stems from the asymmetric nature of the 2,4-furandicarboxylic acid monomer. A combination of vibrational spectroscopy (infrared, Raman and inelastic neutron scattering) and ab initio calculations has been used to assess the conformational and regiochemistry preferences of 2,4-PEF. The latter polymerizes following a random distribution of monomer orientation, thereby rendering the formation of periodic interchain C-H···O contacts wholly unfeasible and ultimately favoring the formation of randomly coiled chains based on gauche-ethylene glycol segments. In the absence of C-H···O stabilization, the ordered crystalline arrangement is disfavored and polymer chains - adopting several quasi iso-energetic structures - prefer to solidify into an amorphous mess.

Nanosized MoO2 can be prepared by different protocols, which yield different morphologies of the nanoparticles. Among their many properties, they can serve as catalysts for styrene oxidation (among other olefins), which is an industrially relevant transformation. In this work, we prepared MoO2 nanosized catalysts by two slightly different hydrothermal protocols using ethylenediamine and either Fe2O3 or hydroquinone. When used in catalysis, kinetic data evidenced that depending on the synthesis protocol of MoO2, induction periods occur (for the catalyst prepared with hydroquinone) with obvious different kinetic profiles and, in addition, product selectivity was also affected. To gain some insight on what is behind these results of the catalytic activity, a combined approach of studies has been conducted. DRIFT and inelastic neutron scattering (INS) techniques were used to assess the adsorbed species at the surface of both the fresh (DRIFT and INS) and recovered (INS) catalysts. Results from this study showed that when hydroquinone was used, an organic shell coated the MoO2 nanoparticles, which negatively influenced the catalytic performance.

The two layered double hydroxides ZnAl-LDH and MgAl-LDH were functionalized with bis(4-HOOC-phenyl)-acenaphthenequinonediimine) (H2BIAN), leading to the intercalation of its dianion, which in a second step reacted with [Mo(CO)3X2(NCMe)2] (X = I, Br), affording four new materials. These materials and the two complexes [Mo(CO)3X2(H2BIAN)2] (X = I, Br) were tested in the olefin epoxidation reaction with substrates cis-cyclooctene, styrene, 1-octene, trans-hex-3-en-1-ol, and R-(+)-limonene, using tert-butylhydroperoxide (tbhp) as oxidant. The new catalysts were particularly good for cis-cyclooctene and styrene (100% conversions) and at least one heterogeneous catalyst was comparable to the homogeneous ones in the epoxidation of 1-octene and trans-hex-3-en-1-ol. The homogeneous catalysts were the best to oxidize R-(+)-limonene (higher conversions).

This work presents a comprehensive spectroscopic analysis of crystalline isoniazid, one of the main drugs in tuberculosis chemotherapy, using a blend of spectroscopic and computational methods. Mid- and far-infrared, Raman, and inelastic neutron scattering spectroscopies, with contribution of isotopic substitution are combined with discrete and periodic DFT quantum chemical calculations. This combined approach successfully reproduces the whole spectral range, allowing a sound assignment of all the vibrational bands. Previous misassignments have been corrected and several spectral features of isoniazid crystal are reported for the first time. Virtues and limitations of the computational approach (periodic and discrete) are also discussed in light of the present state-of-the-art in the field.

A thorough vibrational spectroscopy and molecular modeling study on poly(ethylene 2,5-furandicarboxylate) (PEF) explores its conformational preferences, in the amorphous and crystalline regions, while clarifying structure–property correlations. Despite the increasing relevance of PEF as a sustainable polymer, some of its unique characteristics are not yet fully understood and benefit from a deeper comprehension of its microstructure and intermolecular bonding. Results show that in the amorphous domains, where intermolecular interactions are weak, PEF chains favor a helical conformation. Prior to crystallization, polymeric chains undergo internal rotations extending their shape in a zigzag pattern—an energetically unfavorable geometry which is stabilized by C–H···O bonds among adjacent chain segments. The zigzag conformation is the crystalline motif present in the α and β PEF polymorphs. The energy difference among the amorphous and crystalline chains of PEF is higher than in PET poly(ethylene terephthalat...

Au nanoparticles (AuNPs) were immobilized on S-containing amino acids (cysteine and methionine) Mg/Al hydrotalcite clay in both bulk and exfoliated (colloidal) forms. The Au nanoparticles were prepared by a biomimetic method using an anti-oxidant tea extract to reduce the Au salt solution. The performance of bulk and exfoliated clays with Au nanoparticles in aerobic olefin epoxidation was assessed with very interesting results. Both catalysts were very active towards the epoxide products; selectivity was found to be dependent on the catalyst form. The exfoliated catalysts yielded higher product stereoselectivity in the case of limonene epoxidation. These results can be explained by the existence of a confined environment around the AuNPs structures provided by the clay nanosheets wrapping the nanoparticles, modulating how substrates interact with the catalytic active centres. Based on experimental data mechanistic proposals were also rationalized for these catalysts showing how they assist the catalytic process.

Layered double hydroxides (LDHs) have attracted attention as green materials due to their catalytic ability in benign aqueous solvents. We here demonstrate the synthesis of colloidal Co–Al LDH nanoclusters with an average size of

Background: Aescin, a natural mixture of saponins occurring in Aesculus hippocastanum, exhibits important flebotonic properties, being used in the treatment of chronic venous insufficiency in legs. The inclusion of aescin into cyclodextrins (CDs) is a technical solution for its incorporation into the textile of stockings, but details of the physicochemistry of these host–guest systems are lacking. This work investigates the inclusion of aescin into the cavities of two native cyclodextrins, β-CD and γ-CD.Results: The continuous variation method applied to aqueous-phase 1H nuclear magnetic resonance (1H NMR) has demonstrated that the preferred CD/aescin inclusion stoichiometries are 2:1 with β-CD and 1:1 with γ-CD. The affinity constant calculated for γ-CD·aescin was 894 M−1, while for 2β-CD·aescin it was estimated to be 715 M−1. Density functional theory (DFT) calculations on the interaction of aescin Ib with CDs show that an inclusion can indeed occur and it is further demonstrated that the wider cavity of γ-CD is more adequate to accommodate this large guest. ROESY spectroscopy is consistent with the formation of a complex in which the triterpenic moiety of aescin is included into the cavity of γ-CD. The higher stability of this geometry was confirmed by DFT. Furthermore, DFT calculations were applied to determine the chemical shifts of the protons H3 and H5 of the CDs in the optimised structures of the inclusion complexes. The calculated values are very similar to the experimental data, validating the approach made in this study by NMR.Conclusion: The combination of experimental data from aqueous-state NMR measurements and theoretical calculations has demonstrated that γ-CD is the most suitable host for aescin, although the inclusion also occurs with β-CD. The geometry of the γ-CD·aescin complex is characterised by the inclusion of the triterpene segment of aescin into the host cavity.

A Co/Al layered double hydroxide material was synthesized in both bulk and exfoliated (colloidal) forms. Anion exchange with methionine allowed immobilization of Au nanoparticles previously prepared by a biomimetic method using an anti-oxidant tea aqueous extract to reduce the Au salt solution. The catalytic performance of bulk and exfoliated clays Au-hybrid materials was assessed in aerobic olefin epoxidation. Both catalysts were very active towards the epoxide products and with very interesting substrate conversion levels after 80 h reaction time. The Au-exfoliated material, where the nanosheets work as large ligands, yielded higher product stereoselectivity in the case of limonene epoxidation. This arises from a confined environment around the Au nanoparticles wrapped by the clay nanosheets modulating access to the catalytic active centres by reagents. Mechanistic assessment was also accomplished for styrene oxidation by DFT methods.

A 2:1 Co/Al layered double hydroxide (LDH) material was synthesized with Cl– anions intercalated and then anion exchanged with deprotonated methionine. This allowed further immobilization of Au nanoparticles. The catalytic performance of the set of three LDH materials for comparative benchmarking was assessed in the aqueous reduction of nitroaromatic compounds and of rhodamine dyes in the presence of NaBH4. All catalysts were found to be very active for the nitro-to-amine reduction. The same was observed for the dyes, where reduction rhodamine 6G was faster than that of rhodamine B, for all catalysts. While the Au-containing catalyst was apparently the one showing the best catalytic activity the LDH with Cl– was found to follow it closely in terms of catalytic performance. In addition, while the LDH catalyst with Au was prone to deactivation by amine products in recycling experiments, the LDH catalyst with Cl– was almost insensitive to that, which is a large advantage. These results showed that using a catalyst based on first-row metals for efficient processes is possible and addresses current sustainable and environmental concerns.

Iron oxide magnetic nanoparticles were synthesized with different sizes (11 and 30 nm). Subsequently they were shelled with a silica layer allowing grafting of an organic phosphine ligand that coordinated to the [MoI2(CO)3] organometallic core. The silica layer was prepared by the Stöber method using either mechanical (both 11 and 30 nm nanoparticles) or ultrasound (30 nm only) stirring. The latter nanoparticles once coated with silica were obtained with less aggregation, which was beneficial for the final material holding the organometallic moiety. The Mo loadings were found to be 0.20, 0.18, and 0.34 mmolMo·g−1 for MNP30-Si-phos-Mo,MNP11-Si-phos-Mo, and MNP30-Sius-phos-Mo, respectively, with the ligand-to-metal ratio reaching 4.6, 4.8, and 3.2, by the same order, confirming coordination of the Mo moieties to two phos ligands. Structural characterization obtained from powder X-ray diffraction (XRD), scanning electron microscopy (SEM)/ transmission electron microscopy (TEM) analysis, and Fourier-transform infrared (FTIR) spectroscopy data confirmed the successful synthesis of all nanomaterials. Olefin epoxidation of several substrates catalyzed by these organometallic nano-hybrid materials using tert-butyl hydroperoxide (tbhp) as oxidant, achieved very good results. Extensive testing of the catalysts showed that they are highly active, selective, recyclable, and efficient concerning oxidant consumption.

The Mo(II) complexes [MoX 2 (CO) 3 (BDC)] (X = I, Br; H 2 BDC = 2,2′-bipyridine-5,5′-dicarboxylic acid) were immobilized by intercalation in two layered double hydroxides (LDH), containing Zn/Al (synthesized) and Mg/Al (commercial), as shown by infrared and 13 C solid state NMR spectroscopies, and X-ray powder diffraction. Their catalytic activity was studied in olefin oxidation, using as oxidant tert -butylhydroperoxide (tbhp), and was compared with the activity of the related [MoX 2 (CO) 3 (bpy)] complexes (bpy = 2,2′-bipyridine). cis -Cyclooctene, styrene, 1-octene, trans -hex-3-en-1-ol, and R -(+)-limonene were the substrates tested. All the catalyst showed in average a high selectivity toward the epoxide of each substrate (above 90%, except for styrene), with variable conversions, but none of the heterogeneous catalysts proved to be more active than the homogeneous ones. The same or higher activity in a second catalytic run, as observed in most reactions, suggests a good recycling capability.

MoO2 nanoparticles with tremella-like morphology have been synthesized and characterized. Characterization by powder X-ray diffraction (XRD) and transmission electron micrographs (TEM) microscopy made possible to estimate that the nanosheets have ca. 12 nm and aggregate to form tremella-like structures. The resulting MoO2 nanoparticles were used as catalyst for epoxidation of several olefins. The use of tert-butylhydroperoxide (tbhp), H2O2 and cumenehydroperoxide (chp) as oxygen sources was screened under different reaction conditions, namely, solvent and temperature. The results from the catalytic experiments show that this catalyst was very efficient leading to very high conversion and product selectivity levels. In addition, the use of oxidant:olefin ratios close to 1 show that this catalyst is very efficient conducting olefin epoxidation. Further details are discussed in the work. The catalyst showed overall excellent performance with tbhp. When using H2O2, the catalyst showed good activity, which is very relevant as well. All these achievements contribute with a step forward in the development of more environmentally friendly processes.

The present work aims at exploiting a polyelectrolyte nanocomposite based on poly(4-styrene sulfonic acid) (PSSA) and bacterial cellulose (BC) as an eco-friendly proton-exchange membrane (PEM) for application in microbial fuel cells (MFCs). The PSSA/BC-based PEM was confirmed as a true nanocomposite by inelastic neutron scattering (INS) vibrational spectroscopy. Moreover, this PEM exhibited thermal stability up to 155 °C, Young's modulus of 11.7 ± 0.9 GPa, ion exchange capacity of 1.85 mmol g−1, and maximum protonic conductivity of 1.73 S m−1. The application of the PSSA/BC nanocomposite membrane in a single-chamber lab-scale MFC with a pure culture of Shewanella frigidimarina yielded a maximum power density of 2.42 mW m−2, open circuit voltage of 0.436 V, and internal resistance of 15.1 kΩ. These results are superior to those obtained with a commercial Nafion® membrane and, thus, confirm the potential of this bio-based PSSA/BC nanocomposite as a PEM for MFCs.

International audience

We present a case study on the vibrational coupling of lattice phonons to the electronic 4f7 (8S7/2)–4f65d1 (eg) transition of divalent europium in the hydrides and deuterides LiMH3 and LiMD3 (M = Sr and Ba). For low doping concentrations, these compounds show extraordinarily well-resolved vibronic fine structures at low temperatures. Besides luminescence emission spectroscopy of the europium-doped compounds, we carried out inelastic neutron scattering (INS) experiments of the europium-free compounds. The phonons coupling to the electronic transition are identified, and a good agreement between the vibronic and the INS data is found. The frequencies of the low-energy acoustic modes do not significantly change upon replacing hydride by deuteride, whereas a decrease by a factor of approximately 2 can be observed for the higher energy optic modes. Furthermore, we compare these experimental results to density functional calculations performed with the Vienna Ab initio Simulation Package. Knowledge of the phon...

This work explores the dynamics of hydrogen bond networks in cellulose through inelastic neutron scattering (INS) and periodic CASTEP calculations. Estimated spectra were based on the crystal structure of cellulose Iα and Iβ and replicate the INS spectrum of cellulose samples with remarkable similarity, allowing a reliable assignment of INS bands to vibrational modes of cellulose. Comparison of cellulose samples from varied sources, from bacterial to kraft pulp, allows the identification of characteristic INS bands, arising from C2-OH torsional motions, which easily identify which allomorph-Iα or Iβ-is prevalent. A high crystallinity index is revealed by the presence of well-defined INS bands associated with highly cooperative CH bending modes along the chain. Hydrating kraft cellulose samples clearly affects those INS bands related with the hydroxymethyl group, identified as the preferred binding site for water molecules. At high humidity content level, a significant proportion of the water molecules is aggregated in clusters within the amorphous cellulose domains. The formation of ice microcrystals leads to a partial disruption of the hydrogen-bond network, as can be concluded from the observed red-shift of the torsional OH vibrational modes. The full assignment and interpretation of cellulose's INS spectra herein provided is a sound basis for future use of INS spectroscopy in the characterization of functionalized cellulose fibers and composite materials.

The solids choline chloride and urea, mixed in a 1 : 2 molar proportion, form the iconic deep eutectic solvent “Reline”. A combination of computational and vibrational spectroscopy tools, including inelastic neutron scattering (INS), have been used to probe intermolecular interactions in the eutectic mixture. Reline's experimental spectra were estimated using discrete and periodic ab initio calculations of a molecular aggregate with two choline chloride and four urea units. This is the minimum size required to achieve satisfactory agreement with experiment, as smaller clusters cannot represent all of reline's significant intermolecular interactions. The INS spectrum of reline, compared with that of pure choline chloride, reveals a displacement of chloride anions away from their preferred positions on top of choline's methyl groups, whose torsional movement becomes less hindered in the mixture. Urea, which adopts a planar (sp2) shape in the crystal, becomes non-planar (sp3) in reline, a feature herein discussed for the first time. In reline, urea molecules form a wide range of hydrogen bonds, from soft contacts to stronger associations, the latter being responsible for the deviation from ideality. The chloride's interactions with choline are largely conserved at the hydroxyl end while becoming weaker at the cationic headgroup. The interplay of soft and strong interactions confers flexibility to the newly formed hydrogen-bond network and allows the ensemble to remain liquid at room temperature.

The inelastic neutron scattering (INS) spectra of cyclopentanone were obtained for pure and 50% CCl4 solution forms. Spectra are compared with infrared and Raman data, and with DFT calculated eigenvectors. This exercise aims to find spectroscopic evidence in the neutron spectra for the presence of C–H⋯O hydrogen bonds. These are weak interactions with an energy of ca. −6 kJ mol−1 as predicted by DFT. The neutron spectra show narrow and sharp bands which allows for an assignment of the vibrational modes. The simulated neutron spectrum of C–H⋯O bonded cyclopentanone dimers matches the experimental spectrum of the pure compound, whereas the monomer simulation monomer matches the experimental spectrum of the diluted solution, meaning that such interaction can be probed by INS. Assignment of the 95 cm−1 band to the νH⋯O anti-translational mode, being supported by DFT results and in agreement with previous literature data, is considered and discussed.

Styrene oxidation mediated by a Mo-based mesoporous catalyst can yield selectively styrene oxide or benzaldehyde. Kinetic data evidenced that styrene oxide is the initial single-product formed by the catalytic Mo-mediated process. However, after some hours of reaction benzaldehyde yield rises while that of the epoxide decreases concomitantly. The mechanistic proposal pointed to a surface assisted acid–base mechanism by which styrene oxide is interconverted into benzaldehyde through over-oxidation and cleavage of the C–C bond and releases formaldehyde as well. In an attempt to gain some insight into whether this mechanistic proposal is realistic we have conducted a combined DRIFT and inelastic neutron scattering (INS) study to assess the adsorbed species at the catalyst's surface and confirm the mechanistic proposal. INS and DRIFT provided complementary insight into surface-adsorbed species by probing donor (INS) and acceptor (DRIFT) species. INS also allowed for an estimation of product selectivity by means of a Job method stressing the power of the technique.

International audience; Increasing attention has been dedicated to the development of nanomaterials rendering green and sustainable processes, which occur in benign aqueous reaction media. Herein, we demonstrate the synthesis of another family of green nanomaterials, layered double hydroxide (LDH) nanoclusters, which are concentrated (98.7 g/L in aqueous solvent), stably dispersed (transparent sol for >2 weeks), and catalytically active colloids of nano LDHs (isotropic shape with the size of 7.8 nm as determined by small-angle X-ray scattering). LDH nanoclusters are available as colloidal building blocks to give access to meso- and macroporous LDH materials. Proof-of-concept applications revealed that the LDH nanocluster works as a solid basic catalyst and is separable from solvents of catalytic reactions, confirming the nature of nanocatalysts. The present work closely investigates the unique physical and chemical features of this colloid, the formation mechanism, and the ability to act as basic nanocatalysts in benign aqueous reaction systems.

Reaction of [MnIII(acac)3] and [VIVO(acac)2] with the 1,4-diazabutadiene (DAB) ligands Ph–DAB–(CH2)3R [R = Si(OEt)3(1a); H (1b)] (L) leads to complexes of the type [MnII(acac)2L] and [VIVO(acac)L]Cl in good yields. These complexes were characterised by spectroscopic techniques, and magnetic measurements showed that in the case of the manganese the metal was reduced during the reaction with the nitrogen ligand. The oxovanadium and manganese complexes bearing the ligand with triethoxysilyl groups Ph–DAB–(CH2)3Si(OEt)3(1a) were immobilised in ordered MCM-41 by carrying out a grafting reaction. Tethered complexes of the same type were prepared by treating MCM-41 first with a toluene solution of 1a under reflux; manganese(III) and oxovanadium(IV) precursors were then introduced into the MCM-41-ligand by pore volume impregnation of complex solutions. The modified materials were characterised by powder X-ray diffraction, solid-state NMR (13C, 29Si), FTIR, thermogravimetric studies and low temperature nitrogen adsorption isotherms. The grafted materials contained 0.7 wt% Mn and 0.8 wt% V, while higher metal loadings were achieved when the materials were prepared by tethering (2.9 wt% Mn and 2.4 wt% V). The modified materials are active catalysts for the oxidation of cis-cyclooctene using tert-butylhydroperoxide as oxygen donor, at 328 K, yielding 1,2-epoxycyclooctane as the main reaction product and 1,2-cyclooctanediol as a by-product. The vanadium-containing materials are more efficient epoxidation catalysts than the manganese ones. The catalytic behaviour of the heterogenised catalysts was also compared with that observed in homogeneous phase for the complexes [Mn(acac)2L] and [VO(acac)L]Cl. The vanadium catalysts exhibited the highest catalytic activity, whereas the manganese catalysts were the least active and selective to epoxide formation.

A new organic–inorganic hybrid mesoporous MCM-41 type material has been synthesised by co-condensation of tetraethyl orthosilicate (TEOS) and 1,4-diazobutadiene (DAB) ligand RN C(Ph)–C(Ph) NR where R = (CH 2 ) 3 Si(OEt) 3 , in the presence of cetyltrimethylammonium bromide as the structure-directing agent. Surfactant extraction using acidified methanol leaves a hybrid mesoporous material with periodical hexagonal channels, large pore volume and high specific surface area. The material was characterised by powder X-ray diffraction, transmission electron microscopy, nitrogen gas adsorption, 13 C and 29 Si solid-state NMR, FTIR, elemental and thermogravimetry. The ordered structure and the integrity of the ligand structure are preserved after the extraction step.

A regular MCM-41 type mesostructured silica was used as a support for the incorporation of the highly luminescent tris(beta-diketonate) complex Eu(tta)(3)ephen yielding the hybrid MCM-Eu material. Suitable characterization by powder X-ray diffraction (XRD), thermogravimetric analyses (TGA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), C-13 and Si-21 solid state NMR spectroscopy and photoluminescence was accomplished. The combination of ultraviolet-visible spectroscopy (UV-Vis) and photoluminescence techniques shows that the complex incorporation seems to modify essentially the second Eu3+ coordination shell. For a material that has a simply impregnated lanthanide complex, the herein reported maximum D-5(0) quantum yield value of 0.31 is a significantly high value, being almost in the same scale of the values obtained for the materials with covalently bonded complexes. A detailed theoretical photoluminescence study of the MCM-Eu with the recently developed Luminescence Package - LUMPAC is presented. The high accuracy of the theoretical calculations is achieved through the comparison with the experimental values. Aiming at a deeper understanding of the photoluminescence process, the ligand-to-Eu3+ intramolecular energy transfer and back-transfer rates were also predicted. The dominant pathway involves the energy transfer between the lowest energy ligand triplet and the D-5(0) level (9.70 x 10(7) s(-1)).

The -substituted -diketonate [Ln(3Cl-acac)(3)(H2O)(2)] [Ln=Tb, Gd] complexes (with 3Cl-acac(-) being 3-chloro-2,4-pentanedionate) were characterized by elemental analysis, infrared, ultraviolet (UV)-visible and photoluminescence spectroscopies. For comparison purposes regarding photoluminescence, the well-known [Tb(acac)(3)(H2O)(2)] complex was also synthesized. By considering the phosphorescence spectra of [Gd(3Cl-acac)(3)(H2O)(2)], the effect of chloride replacement of hydrogen on the triplet state energy of the 3Cl-acac ligand was revealed. To support the interpretation and rationalization of the experimental results, Time-dependent DFT calculations were performed on Tb(3Cl-acac)(3)(H2O)(2). Additionally, the possibility of Tb(3Cl-acac)(3)(H2O)(2) to be used as potential green-emitting phosphor material for solid-sate light emitting diodes was evaluated. A prototype was successfully fabricated coating a near-UV LED (370nm) with the Tb(3Cl-acac)(3)(H2O)(2) complex.

12 pages; The lithium salt of the anionic SPS pincer ligand composed of a central hypervalent 4-phosphinine ring bearing two ortho-positioned diphenylphosphine sulfide side arms reacts with [Mn(CO)5Br] to give fac-[Mn(SPS)(CO)3]. This isomer can be converted photochemically to mer-[Mn(SPS)(CO)3], with a very high quantum yield (0.80 ± 0.05). The thermal backreaction is slow (taking ca. 8 h at room temperature), in contrast to rapid electrode-catalyzed mer-to-fac isomerization triggered by electrochemical reduction of mer-[Mn(SPS)(CO)3]. Both geometric isomers of [Mn(SPS)(CO)3] have been characterized by X-ray crystallography. Both isomers show luminescence from a low-lying 3IL (SPS-based) excited state. The light emission of fac-[Mn(SPS)(CO)3] is largely quenched by the efficient photoisomerization occurring probably from a low-lying Mn-CO dissociative excited state. Density functional theory (DFT) and time-dependent DFT calculations describe the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of fac- and mer-[Mn(CO)3(SPS)] as ligand-centered orbitals, largely localized on the phosphinine ring of the SPS pincer ligand. In line with the ligand nature of its frontier orbitals, fac-[Mn(SPS)(CO)3] is electrochemically reversibly oxidized and reduced to the corresponding radical cation and anion, respectively. The spectroscopic (electron paramagnetic resonance, IR, and UV-vis) characterization of the radical species provides other evidence for the localization of the redox steps on the SPS ligand. The smaller HOMO-LUMO energy difference in the case of mer-[Mn(CO)3(SPS)], reflected in the electronic absorption and emission spectra, corresponds with its lower oxidation potential compared to that of the fac isomer. The thermodynamic instability of mer-[Mn(CO)3(SPS)], confirmed by the DFT calculations, increases upon one-electron reduction and oxidation of the complex.

Following a computational-experimental approach, a highly luminescent beta-diketonate-europium(III) complex containing 2-thenoyltrifluoracetonate (tta(-)) and 5,6-epoxy-5,6-dihydro-[1,10] phenanthroline (ephen) ligands, Eu(tta)(3)ephen (II), was theoretically studied by DFT/TD-DFT calculations, synthesized from Eu(tta)(3)(H2O)(2)(I) and fully characterized by high resolution mass spectrometry, TGA analysis, vibrational, UV-Vis and photoluminescence spectroscopy. For intramolecular energy transfer analysis purpose, Ln(NO3)(3)(ephen)(2) [Ln = Eu (III), Gd (IV)] complexes were also synthesized and complexes I and III were theoretically studied. The organic-inorganic tri-ureasil matrix was used as a support for the immobilization of complex II and two hybrid samples were synthesized as a monolith (MtU5Eu-II) and as a thin film (FtU5Eu-II), characterized and its photoluminescence properties were compared with those of complex II. The photophysical properties of complex II benefit from the synergy between the excited-states of both ligands that create efficient energy transfer pathways to optimize the Eu3+ sensitization contributing to the large emission quantum yield (82 +/- 8%), which is one of the highest so far reported for solid lanthanide beta-diketonate complexes. Moreover, although the incorporation of complex II into the hybrid matrix is disadvantageous from the quantum yield point of view, MtU5Eu-II and FtU5Eu-II exhibit the highest emission quantum yields reported so far for Eu3+-containing hybrids (63 +/- 6% and 48 +/- 5%, respectively). Additionally, a significant improvement in the photostability under UV irradiation of the incorporated complex II is observed. The possibility of FtU5Eu-II to be used as a luminescent solar concentrator was evaluated and an optical conversion efficiency of similar to 9% as well as an ability to boost up the Si-photovoltaic cell output to 0.5% were verified.