Solid-state Spectroscopy Research Articles

Solid-State Replacement in the Polyhedra of Cu2+, Ni2+, and Co2+ upon Dehydration/Rehydration Processes Associated with a Color Change in Three Isomorphous Materials with 5,5'-Indigodisulfonate.

The significance of thermochromic materials in a wide range of applications makes their research and development highly desirable. Herein, three new thermochromic isomorphous supramolecular materials based on the 5,5'-indigodisulfonate ion of the indigo carmine dye, with formulas [Cu(H2O)6](C16H8N2O8S2)·2H2O (1), [Ni(H2O)6](C16H8N2O8S2)·2H2O (2), and [Co(H2O)6](C16H8N2O8S2)·2H2O (3), are reported. These materials exhibit thermochromic properties, with a color change from red-bronze to grayish-red after the first step of their dehydration process completed around 80 °C (conversion of 1 to [Cu(H2O)2(C16H8N2O8S2) (1')]), and then, this grayish-red color becomes lighter after the second step, which is completed around 230 °C (conversion of 1' to [Cu(C16H8N2O8S2)] (1d)). The 1, 1', and 1d phases have different crystal structures but similar tetragonal bipyramidal geometries around the copper ions. These dehydrated phases rehydrate by exposure to a higher humidity level. Solid-state UV-visible spectroscopy, thermogravimetric analysis, infrared spectroscopy, and X-ray powder diffraction analyses shed light on the structural and chemical changes accompanying the color change of 1, 2, and 3 to their partial dehydrated phases 1', 2', and 3', respectively. These transformations occur with the small modification of the charge transfer energy in the 5,5'-indigodisulfonate ions, indicating the potential of dye-based metall-organic materials for chromic properties.

Merocyanines: Electronic Structure and Spectroscopy in Solutions, Solid State, and Gas Phase.

Merocyanines, owing to their readily tunable electronic structure, are arguably the most versatile functional dyes, with ample opportunities for tailored design via variations of both the donor/acceptor (D/A) end groups and π-conjugated polymethine chain. A plethora of spectral properties, such as strong solvatochromism, high polarizability and hyperpolarizabilities, and sensitizing capacity, motivates extensive studies for their applications in light-converting materials for optoelectronics, nonlinear optics, optical storage, fluorescent probes, etc. Evidently, an understanding of the intrinsic structure-property relationships is a prerequisite for the successful design of functional dyes. For merocyanines, these regularities have been explored for over 70 years, but only in the past three decades have these studies expanded beyond the theory of their color and solvatochromism toward their electronic structure in the ground and excited states. This Review outlines the fundamental principles, essential for comprehension of the variable nature of merocyanines, with the main emphasis on understanding the impact of internal (chemical structure) and external (intermolecular interactions) factors on the electronic symmetry of the D-π-A chromophore. The research on the structure and properties of merocyanines in different media is reviewed in the context of interplay of the three virtual states: nonpolar polyene, ideal polymethine, and zwitterionic polyene.

Investigation of the Effect of Oxide Additives on the Band Gap and Photocatalytic Efficiency of TiO2 as a Fixed Film.

The effects of various additives (Y2O3, Ga2O3, and WO3) on photocatalytic degradation efficiency under UV light-emitting diodes (LEDs) and the optical properties of TiO2 Degussa P25 were investigated using ketoprofen and diclofenac, two non-steroidal anti-inflammatory drugs commonly detected in German rivers. Experimental results demonstrated that thin films containing these additives exhibited similar photocatalytic degradation efficiencies as pure TiO2, achieving a 30% degradation of ketoprofen over 150 min. In contrast, the Y2O3/TiO2 thin film showed significantly improved performance, achieving a 46% degradation of ketoprofen in 180 min. Notably, the Y2O3/TiO2 system was three times more effective in degrading diclofenac compared to pure TiO2. Additionally, the Y2O3/TiO2 photocatalyst retained its activity over three successive cycles with only a slight decrease in efficiency. The photocatalytic degradation of both organic pollutants followed first-order kinetics with all photocatalysts. The investigation included SEM imaging to assess the surface homogeneity of the thin films and UV-vis solid-state spectroscopy to evaluate the impact of the additives on the energy band gap of TiO2.

Dynamic visualization level 3 details of latent fingerprints by fluorescence imaging and photoluminescent macromolecules functionalized with spiropyran photoswitch

Detecting latent fingerprints (LFPs) poses a considerable challenge for individual identification in the case of the criminal scene because detecting more details about three levels of identification patterns at a fast rate and by conventional instruments is very important for investigators. This research involved creating nanoparticles made of a copolymer containing tertiary amine-functionalized methacrylate through emulsion copolymerization, and then modifying them with a spiropyran derivative. The concentration of tertiary amine groups significantly influenced the optical properties, with samples containing more than 10 wt% exhibiting negative photochromism, leading to the absence of dynamic emission and reversible photochromism. The study of the kinetics of isomerization from spiropyran to merocyanine using solid-state fluorescence spectroscopy highlighted the important role of negative photochromism in the photoswitching of spiropyran. The resulting dynamic photoluminescent polymer powders were effectively utilized for LFP visualization through powder dusting, fluorescence imaging, optical security tag production, and the development of innovative OLEDs. The study confirmed the efficiency of these polymer powders in visualizing LFPs, enabling the identification of intricate details and patterns at three distinct levels. The observed LFPs emitted fluorescence in a range of colors, displaying high contrast, resolution, maximum intensity, and brightness. Three levels of identification details were detected for an unknown LFP that remained on the surface of the glass bottle as a real sample in the criminal scene. Successful identification of the unknown offender indicates the potential application of samples for time-dependent visualization of LFPs in criminal scenes.

(Invited) From Inside Out: How Synthesis-Structure Correlations Conspire to Determine Photoluminescence Traits and Operational Robustness in Non-Blinking Giant Quantum Dots

“Giant” or thick-shell core/shell quantum dots (gQDs) are an important class of solid-state quantum emitter. Without any encapsulation gQDs are characterized by strongly suppressed blinking, or even non-blinking behavior, and resistance to photobleaching at room temperature. In addition, non-radiative Auger processes are significantly reduced in this class of luminescent nanomaterial. Together, these qualities lead to novel functionality as photon sources for a range of ensemble and single-emitter applications, including down-conversion phosphors, direct excitation light-emitting diodes, single-biomolecule tracking, and single-photon generation. For many applications, operation at elevated temperature and under intense photon flux is also desired, and we have shown that gQDs outperform other emitters in this key metric of operational robustness. Interestingly, performance under these conditions is strongly dependent on the synthetic method employed for shell growth. Previously we revealed the mechanistic pathways responsible for thermally-assisted photodegradation, distinguishing effects of hot-carrier trapping and QD charging (ACS Nano 2018, 12, 5, 4206), and subsequently used solid-state spectroscopy to obtain kinetic and thermodynamic parameters of the photothermal degradation process (ACS Appl. Mater. Interfaces 2020, 12, 27, 30695). Here, I will discuss a comprehensive analysis of gQD structural properties from the inside of the nanocrystal to its surface and demonstrate correlations between specific structural features and both causal synthetic parameters and resulting performance metrics. Two synthetic methods—successive-ionic-layer-adsorption-and-reaction and high-temperature continuous-injection—will be compared. Investigated structural features will include interfacial alloying, stacking-fault density and surface-ligand identity, while correlated functionalities will address quantum yield, single-gQD photoluminescence under thermal/photo-stress, charging behavior and quantum-optical properties. I will show several unexpected conclusions, including the surprising finding that while interfacial alloying is the strongest indicator of gQD stability under stress, the parameter is not the determining factor for Auger suppression. Furthermore, quantum yield is strongly influenced by surface chemistry and can approach unity even in the case of a gQD comprising a thick shell with a high defect density with proper choice of excitation wavelength. Interestingly, we find a strong correlation between the existence of zinc-blende stacking faults and whether the gQD exhibits charged-state or purely excitonic emission, and the interplay between charged emission and excitonic emission can be precisely tuned by “mixing” shell-growth methods (Small Sci. 2023,3, 2300092).

Acidic pathway in formation of SiO2–AlO2–PO2 geopolymeric ceramic: Investigation of structural evolution and electrical behaviour

The investigation into the acidic pathway in geopolymer formation has been overlooked compared to the alkaline pathway. This study seeks to fill the gap by exploring the development mechanism and electrical properties of this type of geopolymer. The microstructural properties of geopolymer ceramics were assessed through the deconvolution of attenuated total reflectance-Fourier-transform infrared spectra (ATR-FTIR), powder X-ray diffraction (PXRD), scanning electron microscopy with energy dispersive spectroscopy (SEM/EDS), simultaneous thermogravimetric analysis and differential thermal analysis (TGA/DTA). Furthermore, the electrical properties of the prepared ceramics were monitored using solid-state impedance spectroscopy (ss-IS). Maintaining an Al to P molar ratio of 1:1, various post-treatment temperatures (60 °C, 105 °C, 300 °C, 1200 °C) were employed to observe their effects on the (micro)structural properties of the samples under investigation. This ratio ensures the formation of an amorphous structure of SiO2·Al2O3·P2O5·nH2O. Additionally, the emergence of new crystalline aluminium and phosphate phases was observed.

Rapid-scan broadband frequency-domain terahertz spectroscopy via dynamic optical phase lock

Frequency-domain terahertz (THz) spectroscopy using photomixing devices has unique advantages such as high dynamic range and high spectral resolution. Thus, many applications for solid-state and gas-phase spectroscopy have been proposed. In this study, we developed a feedback controlled technique to dynamically compensate for the optical phase accompanied by frequency sweep, enabling both fast and high-resolution data acquisition across a wide frequency region. From gas-phase THz spectroscopy measurements of dilute acetonitrile gas in a wide frequency range up to 1.1 THz, fine structures with linewidths less than 10 MHz were clearly resolved, while the data acquisition rate was improved by two orders compared to the previously reported value.

Well-defined nanomagnetic nitrilotriacetic acid complex of Cu(ii) supported on silica-coated nanosized magnetite: a new highly efficient and magnetically separable catalyst for C-N bond formation.

A nitrilotriacetic acid (NTA) complex of Cu(ii) supported on silica-coated nanosized magnetite Fe3O4@SiO2-Pr-DEA-[NTA-Cu(ii)]2 was prepared as a new well-defined magnetically separable nanomaterial and fully characterized via IR, XRD, FESEM, TEM, TGA, DLS, BET, VSM, solid-state UV-vis spectroscopy, EDX, ICP-OES, and FESEM-EDX map analyses. Thereafter, it was successfully applied as a new easily magnetically separable and reusable heterogeneous nanocatalyst for the Buchwald-Hartwig C-N bond formation reaction in DMF at 110 °C. Using this method, various kinds of nitrogen heterocycles, such as imidazoles, 2-methyl-1H-imidazole, benzimidazole, indole, and 10H-phenothiazine as well as aliphatic secondary amines such as piperidine, piperazine, morpholine, dimethylamine, and diethylamine, were reacted with aryl halide compounds, and the desired products were obtained with good to excellent yields. In all cases, the applied catalyst could be recovered easily and rapidly using an external magnet and reused 7 times without significant loss of catalytic activity.

Solid-state NMR assignment of α-synuclein polymorph prepared from helical intermediate

Synucleinopathies are neurodegenerative diseases characterized by the accumulation of α-synuclein protein aggregates in the neurons and glial cells. Both ex vivo and in vitro α-synuclein fibrils tend to show polymorphism. Polymorphism results in structure variations among fibrils originating from a single polypeptide/protein. The polymorphs usually have different biophysical, biochemical and pathogenic properties. The various pathologies of a single disease might be associated with distinct polymorphs. Similarly, in the case of different synucleinopathies, each condition might be associated with a different polymorph. Fibril formation is a nucleation-dependent process involving the formation of transient and heterogeneous intermediates from monomers. Polymorphs are believed to arise from heterogeneous oligomer populations because of distinct selection mechanisms in different conditions. To test this hypothesis, we isolated and incubated different intermediates during in vitro fibrillization of α-synuclein to form different polymorphs. Here, we report 13C and 15N chemical shifts and the secondary structure of fibrils prepared from the helical intermediate using solid-state nuclear magnetic spectroscopy.

Synthesis, Crystal Structure, Fluorescence and Theoretical Calculations of Three Zn(II)/Cd(II) Complexes with Bis-dentate N,N-Quinoline Schiff Base.

Three d10 metal complexes, ZnL(OAc)2 (1), CdL(OAc)2 (2) and [CdL2(NO3)2]·CH3CN (3) were synthesized using the ligand (E)-N-(3-methoxy-4-methylphenyl)-1-(quinolin-2-yl)methanimine (L) and characterized by FT-IR spectra, NMR spectra, and CHN elemental analysis. Single-crystal X-ray diffraction analysis revealed that complexes 1 and 2 are isostructural, with the central metal adopting a hexacoordinate octahedral geometry, while complex 3 adopts a triangular dodecahedron geometry. Thermal gravimetric analysis showed that these complexes exhibit good thermal stability. Solid-state fluorescence spectroscopy measurements demonstrated that complexes 1-3 exhibit bright yellow-green fluorescence (λem = 564nm for 1; 524nm for 2; 542nm for 3), suggesting their potential as photoluminescent materials. Furthermore, DFT calculations, including frontier molecular orbitals, energy levels, and surface electrostatic potential, provided insights into the structural and electronic spectral properties of complexes 1-3.

Structure of vanadia-titania catalysts doped with alkali metals according to solid-state NMR, ESR spectroscopies and DFT

In this work, V/M/TiO2 catalysts (M = Li, Na, K, Rb and Cs) were investigated with Solid-state nuclear magnetic resonance (SSNMR), electron paramagnetic resonance (ESR) and first-principles calculations. The total vanadium content corresponds to half monolayer (4 V atoms·nm−2 of TiO2 support surface), with V/M atomic ratio being 4/0.6. Static 51V and MAS 1H, 7Li, 51V, 23Na, 133Cs NMR spectra were acquired. Surface moieties of vanadium oxide on (001) anatase surface were modeled using density functional theory (DFT); their 51V NMR parameters were calculated with the Gauge-Including Projected Augmented Wave (GIPAW) method and compared to experimental data obtained with 51V SSNMR spectroscopy. It was found that mainly strongly bound vanadium sites (V3) are formed on anatase samples, located on TiO2 terminal oxygen atoms. Weakly bound vanadium sites (V1, V2) are formed on bridged anatase oxygen atoms. Supported alkali metals (Li, Na, K, Rb and Cs) on TiO2 were found to interact with protons located on the terminal and bridged TiO2 oxygen atoms. The relative ratio of weakly bound vanadium sites (V1, V2) increased on alkali-containing samples. Calculations performed showed lithium cation to prefer V-O-Ti or V-O-V bonds over VO, unsystematically deshielding vanadium nuclei. The presence of V3+ is likely to cause a loss of intensity in 51V NMR spectra.

Tetraphenylethene-based mononuclear aggregation-induced emission (AIE)-active mechanofluorochromism gold(I) complexes with different auxiliary ligands

In this study, a series of tetraphenylethene-containing gold(I) complexes with different auxiliary ligands have been synthesized. These complexes were characterized using a variety of techniques including nuclear magnetic resonance spectroscopy, mass spectrometry, and single crystal X-ray diffraction. Their aggregation-induced emission (AIE) behaviors were investigated through ultraviolet/visible and photoluminescence spectrum analyses, and dynamic light scattering measurements. Meanwhile, their mechanofluorochromic properties were also studied via solid-state photoluminescence spectroscopy. Intriguingly, all these mononuclear gold(I) molecules functionalized by tetraphenylethene group demonstrated AIE phenomena. Furthermore, five gold(I) complexes possessing diverse auxiliary ligands exhibited distinct fluorescence changes in response to mechanical grinding. For luminogens 2–5, their solids showed reversible mechanofluorochromic behaviors triggered by the mutual transformation of crystalline and amorphous states, while for luminogen 1, blue-green-cyan three-color solid fluorescence conversion was realized by sequential mechanical grinding and solvent fumigation. Based on this stimuli-responsive tricolored fluorescence feature of 1, an information encryption system was successfully constructed.

Small electron polarons bound to interstitial tantalum defects in lithium tantalate

The absorption features of optically generated, short-lived small bound electron polarons are inspected in congruent lithium tantalate, LiTaO3 (LT), in order to address the question whether it is possible to localize electrons at interstitial Ta V :V Li defect pairs by strong, short-range electron–phonon coupling. Solid-state photoabsorption spectroscopy under light exposure and density functional theory are used for an experimental and theoretical access to the spectral features of small bound polaron states and to calculate the binding energies of the small bound Ta Li4+ (antisite) and Ta V4+ :V Li (interstitial site) electron polarons. As a result, two energetically well separated ( ΔE≈0.5 eV) absorption features with a distinct dependence on the probe light polarization and peaking at 1.6 eV and 2.1 eV are discovered. We contrast our results to the interpretation of a single small bound Ta Li4+ electron state with strong anisotropy of the lattice distortion and discuss the optical generation of interstitial Ta V4+ :V Li small polarons in the framework of optical gating of Ta V4+ :Ta Ta4+ bipolarons. We can conclude that the appearance of carrier localization at Ta V :V Li must be considered as additional intermediate state for the 3D hopping transport mechanisms at room temperature in addition to Ta Li , as well, and, thus, impacts a variety of optical, photoelectrical and electrical applications of LT in nonlinear photonics. Furthermore, it is envisaged that LT represents a promising model system for the further examination of the small-polaron based photogalvanic effect in polar oxides with the unique feature of two, energetically well separated small polaron states.

Methoxylated bis(pentafluorophenyl)boron‐β‐diketonates: Synthesis, Optical Properties and Hydrolytic Stability

AbstractA series of methoxylated bis(pentafluorophenyl)boron‐β‐diketonates (dkB(C6F5)2) with intense emission has been synthesized and characterized by a variety of physicochemical methods. The photophysical properties of the synthesized compounds were thoroughly investigated by electronic absorption, steady‐state, and time‐resolved fluorescence spectroscopy in both solution and solid state. The studied compounds exhibit solvatochromic behavior attributed to the intramolecular charge transfer (ICT) nature of the first excited state. The formation of exciplexes between DBMB(C6F5)2 and benzene derivatives was also studied. Notably, the studied compounds display a complex luminescence profile in the solid state, featuring fluorescence, delayed fluorescence and phosphorescence emission. Furthermore, the hydrolytical stability of the complexes was assessed, demonstrating excellent resistance to hydrolysis. Estimated rate constants, determined at 60 °C, are significantly lower (90‐2000 times) than those observed for the well‐studied dibenzoylmethanatoboron difluoride (DBMBF2). The incorporation of pentafluorophenyl substituents at the boron atom enables the synthesis of highly fluorescent and hydrolytically stable boron chelate complexes, suitable for sensing and bioimaging applications in water‐containing environments.

Dinitrogen-bridged ruthenium(II) complexes featuring dithiocarbamate ligands

In quest of low molecular weight metal-thiolate complexes as model complexes for nitrogenase, four binuclear ruthenium(II) dinitrogen-bridged complexes featuring dithiocarbamate ligands, [{(Me3tacn)Ru(κ2-S2CNR2)}2(µ-N2)][PF6]2 (Me3tacn = 1,4,7-trimethyl-1,4,7-triazacyclononane; 1, R = Me; 2, R = Et; 3, R = nPr; 4, R = iPr), were synthesized by reduction of [(Me3tacn)RuIII(κ2-S2CNR2)Cl]PF6 with zinc powder in a nitrogen atmosphere. A 16-electron mononuclear ruthenium(II) species [(Me3tacn)Ru(κ2-S2CNnPr2)]PF6 (3′) was isolated during preparation of 3, which may help elucidate the formation of complexes 1-4. Molecular structures of complexes 1, 2, 4 and 3′ were established by single crystal X-ray diffraction analysis. Moreover, complexes 1-4 were characterized by infrared, 1H NMR, UV–vis, fluorescence, Raman (solid state and solution state) spectroscopies and mass spectrometry, and their electrochemical properties were also investigated. Density functional theory (DFT) calculation was performed on complex 2 to study its Lewis structure and explain the UV–vis absorption spectra. Structural and DFT analyses demonstrate that N2 activation is accompanied by electron redistribution of the dithiocarbamate ligands.

Spectroscopic Evidence for Doubly Hydrogen-Bonded Cationic Dimers in the Solid, Liquid, and Gaseous Phases of Carboxyl-Functionalized Ionic Liquids.

Intermolecular interactions determine whether matter sticks together, gases condense into liquids, or liquids freeze into solids. The most prominent example is hydrogen bonding in water, responsible for the anomalous properties in the liquid phase and polymorphism in ice. The physical properties are also exceptional for ionic liquids (ILs), wherein a delicate balance of Coulomb interactions, hydrogen bonds, and dispersion interactions results in a broad liquid range and the vaporization of ILs as ion pairs. In this study, we show that strong, local, and directional hydrogen bonds govern the structures and arrangements in the solid, liquid, and gaseous phases of carboxyl-functionalized ILs. For that purpose, we explored the H-bonded motifs by X-ray diffraction and attenuated total reflection (ATR) infrared (IR) spectroscopy in the solid state, by ATR and transmission IR spectroscopy in the liquid phase, and by cryogenic ion vibrational predissociation spectroscopy (CIVPS) in the gaseous phase at low temperature. The analysis of the CO stretching bands reveals doubly hydrogen-bonded cationic dimers (c═c), resembling the archetype H-bond motif known for carboxylic acids. The like-charge doubly hydrogen-bonded ion pairs are present in the crystal structure of the IL, survive phase transition into the liquid state, and are still present in the gaseous phase even in (2,1) complexes wherein one counterion is removed and repulsive Coulomb interaction increased. The interpretation of the vibrational spectra is supported by quantum chemical methods. These observations have implications for the fundamental nature of the hydrogen bond between ions of like charge.

Structural Insights into Seeding Mechanisms of hIAPP Fibril Formation.

The deposition of islet amyloid polypeptide (hIAPP) fibrils is a hallmark of β-cell death in type II diabetes. In this study, we employ state-of-the-art MAS solid-state spectroscopy to investigate the previously elusive N-terminal region of hIAPP fibrils, uncovering both rigidity and heterogeneity. Comparative analysis between wild-type hIAPP and a disulfide-deficient variant (hIAPPC2S,C7S) unveils shared fibril core structures yet strikingly distinct dynamics in the N-terminus. Specifically, the variant fibrils exhibit extended β-strand conformations, facilitating surface nucleation. Moreover, our findings illuminate the pivotal roles of specific residues in modulating secondary nucleation rates. These results deepen our understanding of hIAPP fibril assembly and provide critical insights into the molecular mechanisms underpinning type II diabetes, holding promise for future therapeutic strategies.

Crystal structures, Hirshfeld surface analysis, thermogravimetric, and spectroscopic properties of three Zn(Ⅱ) complexes bridged by 4,4′-bipy with organic sulfonate anions as counterions

Three Zn(Ⅱ) sulfonate compounds: {[Zn3(Ac)4(4,4′-bipy)4]·2(3-pySO3)·H2O}n (1), {[Zn(4,4′-bipy)(H2O)4]·2(Me-phSO3)}n (2), and {[Zn(4,4′-bipy)(H2O)4]·2(NH2-phSO3)}n (3), were synthesized through solvent diffusion method at room temperature (3-pySO3H = Pyridine-3-Sulfonic acid; Me-phSO3H = P-Toluene Sulfonic acid; NH2-phSO3H = Sulfanilic acid). Single-crystal X-ray diffractions reveal that the crystal structure of compound 1 contains a 2D cationic layer with pseudo-square grid motifs formed by trinuclear Zn(II) units which connected by 4,4′-bipy ligands. Water molecule forms hydrogen bonds with free 3-PySO3− anions which are located in the voids of the cationic grids. Compounds 2 and 3 show isostructural 1D [Zn(4,4′-bipy)(H2O)4]2+ chains with sulfonate anions connected to the chain via hydrogen bonding. The weak interactions in the structures of the three compounds have been assessed using Hirshfeld surface analyses and 2D fingerprint plots. The Hirshfeld surface shows that the most important contributions for the crystal packing are from H···H and H··O/O··H interactions, which indicate dominant van der Waals interactions. In addition, the compounds were investigated by powder X-ray diffraction (PXRD), elemental analyses, UV–vis, FT-IR, solid-state fluorescence spectroscopy, and thermal analyses (TG-DSC).

Molybdenum Complexes Derived from 2-Hydroxy-5-nitrobenzaldehyde and Benzhydrazide as Potential Oxidation Catalysts and Semiconductors.

This study aimed to synthesize molybdenum complexes coordinated with an aroyl hydrazone-type ligand (H2L), which was generated through the condensation of 2-hydroxy-5-nitrobenzaldehyde with benzhydrazide. The synthesis yielded two types of mononuclear complexes, specifically [MoO2(L)(MeOH)] and [MoO2(L)(H2O)], as well as a bipyridine-bridged dinuclear complex, [(MoO2(L))2(4,4'-bpy)]. Those entities were thoroughly characterized using a suite of analytical techniques, including attenuated total reflectance infrared spectroscopy (IR-ATR), elemental analysis (EA), thermogravimetric analysis (TGA), and single-crystal X-ray diffraction (SCXRD). Additionally, solid-state impedance spectroscopy (SS-IS) was employed to investigate the electrical properties of these complexes. The mononuclear complexes were tested as catalysts in the epoxidation of cyclooctene and the oxidation of linalool. Among these, the water-coordinated mononuclear complex, [MoO2(L)(H2O)], demonstrated superior electrical and catalytic properties. A novel contribution of this research lies in establishing a correlation between the electrical properties, structural features, and the catalytic efficiency of the complexes, marking this work as one of the pioneering studies in this area for molybdenum coordination complexes, to the best of our knowledge.

Cu(I) Coordination Compounds Conjugated to Au Nanorods for Future Applications in Drug Delivery: Insights in Molecular, Electronic and Cu Local Structure in Solid and Liquid Phase.

In the framework of the design, synthesis and testing of a library of copper complexes and nanostructured assemblies potentially endowed with antitumor and antiviral activity and useful for several applications, from drugs and related delivery systems to the development of biocidal nanomaterials, we present the detailed spectroscopic investigation of the molecular and electronic structure of copper-based coordination compounds and of a new conjugated system obtained by grafting Cu(I) complexes to gold nanorods. More in detail, the electronic and molecular structures of two Cu complexes and one AuNRs/Cu-complex adduct were investigated by X-ray photoelectron spectroscopy (XPS), synchrotron-induced XPS (SR-XPS) and near edge X-ray absorption spectroscopy (NEXAFS) in solid state, and the local structure around copper ion was assessed by X-ray absorption spectroscopy (XAS) both in solid state and water solution for the AuNRs/Cu-complex nanoparticles. The proposed multi-technique approach allowed to properly define the coordination geometry around the copper ion, as well as to ascertain the molecular structures of the coordination compounds, their stability and modifications upon interaction with gold nanoparticles, by comparing solid state and liquid phase data.