Cationic Counterparts Research Articles

Spectroscopy and dynamics of isolated anions: Versatile instrumentation for photodetachment and photoelectron spectroscopy.

Molecular anions are appealing targets for study because, compared with their neutral and cationic counterparts, they can be probed with conventional laboratory lasers without the need for multiphoton ionization schemes, and they provide spectroscopic details on the corresponding neutral molecules. Here, we describe a section of a modular instrument designed to perform high-throughput photoelectron and photodetachment spectroscopy of gas-phase anions, with future provision for time-resolved and isomer-selective spectroscopy. The instrument framework allows for the incorporation and adaptation of several ion sources, as demonstrated here with plasma (electric) discharge sources providing variable hard to soft ion generation conditions. The generated anions are separated according to their mass-to-charge ratio through time-of-flight mass spectrometry (m/zΔm/z = 500-600) and are focused into a set of perpendicular velocity-map imaging electrodes (ΔEE≈4%), where mass-selected anions are probed using laser light and the ejected electrons are velocity-map imaged. Instrument performance is demonstrated through the acquisition of photodetachment and photoelectron spectra for CH2CN-, showing sharp resonances in the vicinity of the detachment threshold assigned to rovibrational states of a dipole-bound anion and broader lifetime-limited spectral features at photon energies well above the threshold assigned to prompt autodetachment from a temporary anion resonance. Similar measurements could be performed on any molecular anions generated in the sources.

Direct Evidence of the Effect of Water Molecules Position in the Spectroscopy, Dynamics, and Lighting Performance of an Eco-Friendly Mn-Based Organic-Inorganic Metal Halide Material for High-Performance LEDs and Solvent Vapor Sensing.

Luminescent Mn(II)-based organic-inorganic hybrid halides have drawn attention as potential materials for sensing and photonics applications. Here, the synthesis and characterization of methylammonium (MA) manganese bromide ((MA)nBrxMn(H2O)2, (n = 1, 4 and x = 3, 6)) with different stoichiometries of the organic cation and inorganic counterpart, are reported. While the Mn2+ centers have an octahedral conformation, the two coordinating water molecules are found either in cis (1) or in trans (2) positions. The photophysical behavior of 1 reflects the luminescence of Mn2+ in an octahedral environment. Although Mn2+ in 2 also has octahedral coordination, at room temperature dual emission bands at ≈530 and ≈660nm are observed, explained in terms of emission from Mn2+in tetragonally compressed octahedra and self-trapped excitons (STEs), respectively. Above the room temperature, 2 shows quasi-tetrahedral behavior with intense green emission, while at temperatures below 140K, another STE band emerges at 570nm. Time-resolved experiments (77-360K) provide a clear picture of the excited dynamics. 2 shows rising components due to STEs formation equilibrated at room temperature with their precursors. Finally, the potential of these materials for the fabrication of color-tunable down-converted light-emitting diode (LED) and for detecting polar solvent vapors is shown.

Homoleptic Rare-Earth-Metal Sandwiches with Dibenzo[a,e]cyclooctatetraene Dianions.

A family of rare-earth complexes [RE(III) = Y, La, Gd, Tb, Dy, and Er] with doubly reduced dibenzo[a,e]cyclooctatetraene (DBCOT) has been synthesized and structurally characterized. X-ray diffraction analysis confirms that all products of the [RE(DBCOT)(THF)4][RE(DBCOT)2] composition consist of the anionic sandwich [RE(DBCOT)2]- and the cationic counterpart [RE(DBCOT)(THF)4]+. Within the sandwich, two elongated π decks are slightly bent toward the metal center (avg. 7.3°) with a rotation angle of 35.9-37.6°. The RE(III) ion is entrapped between the central eight-membered rings of DBCOT2- in a η8 fashion. The trends in the RE-COT bond lengths are consistent with the variations of the ionic radii of RE(III) centers. The 1H NMR spectra of the diamagnetic Y(III) and La(III) analogues illustrate the distinct solution behavior for the cationic and anionic parts in this series. Magnetic measurements for the Dy analogue reveal single-molecule magnetism, which was rationalized by considering the effect of crystal-field splitting for both building units analyzed by electronic structure calculations.

A rapid access to activity-based and mitochondria targeting rhodol-like chromenoxanthene dyes for selective bioimaging

Chromenoxanthenes are colorful dyes which do not suffer from any fluorescence turn-off induced by spirocyclic forms as usually observed for conventional rhodamine and fluorescein xanthene analogues. In that way, wide variety of applications in particular in bioimaging can be foreseen for those underexplored fluorophores. Herein, a one-pot synthesis of rhodol-like chromenoxanthene dyes is reported, which are further modified at the periphery of the core structure to tune the optical properties. Resulting neutral derivatives are bright fluorophores in the orange-red spectral window, while cationic counterparts are almost non-emissive. These optical properties are fully characterized and are also rationalized via first-principles calculations. In particular, the occurrence of twisted intramolecular charge transfers is shown to account for the dark-state quenching occurring in the charged compounds. This feature is harvested in the construction of an activity-based fluorescent probe for mitochondria imaging. Excellent organelle localization is achieved, while the emission signal is proportional to the hydrogen peroxide concentration in the mitochondria. Furthermore, the absence of cytotoxicity bestows rhodol-like chromenoxanthene dyes a bright future in cellular imaging applications.

Fluoroquinolone-Based Organic Salts (GUMBOS) with Antibacterial Potential.

Antimicrobial resistance is a silent pandemic considered a public health concern worldwide. Strategic therapies are needed to replace antibacterials that are now ineffective. One approach entails the use of well-known antibacterials along with adjuvants that possess non-antibiotic properties but can extend the lifespan and enhance the effectiveness of the treatment, while also improving the suppression of resistance. In this regard, a group of uniform materials based on organic salts (GUMBOS) presents an alternative to this problem allowing the combination of antibacterials with adjuvants. Fluoroquinolones are a family of antibacterials used to treat respiratory and urinary tract infections with broad-spectrum activity. Ciprofloxacin and moxifloxacin-based GUMBOS were synthesized via anion exchange reactions with lithium and sodium salts. Structural characterization, thermal stability and octanol/water partition ratios were evaluated. The antibacterial profiles of most GUMBOS were comparable to their cationic counterparts when tested against Gram-positive S. aureus and Gram-negative E. coli, except for deoxycholate anion, which demonstrated the least effective antibacterial activity. Additionally, some GUMBOS were less cytotoxic to L929 fibroblast cells and non-hemolytic to red blood cells. Therefore, these agents exhibit promise as an alternative approach to combining drugs for treating infections caused by resistant bacteria.

Rational Design for Selective Oxygen Evolution Reaction over CoFeOxHy at High Current Density in the Presence of Chloride Ion

Seawater electrolysis is expected to play an important role in the circular economy by reducing the hydrogen production cost due to the simplified process lines[1] and by saving scarce sources of safe and fresh water.[2] Seawater impurities especially chloride ions can cause the corrosion of the catalyst and be oxidized at high potential, competing with the oxygen evolution reaction (OER). Produced chlorine and hypochlorite are toxic to humans and the environment,[3] thus selective OER is desirable. Furthermore, impurity cations, such as Ca and Mg, may form hydroxide precipitates in a highly alkaline condition which is commonly used in the commercial electrolyzer. Therefore, selective OER in non-extreme pH (pH < 10) is highly desired, which requires additional challenges on the electrocatalyst and the electrolyte. In this study, we have effectively utilized the thermodynamic potential gap between chloride oxidation reaction (COR) and OER, and engineering of non-noble metal hydroxide electrocatalysts and buffer electrolyte successfully achieved the selective OER in the presence of chloride ion at commercially relevant operation conditions in non-extreme pH within the thermodynamic window.Firstly, the stability of non-noble metal materials in 1.0 mol kg− 1 potassium borate (K-borate, pH 9.2) buffer solution with 0.5 mol kg− 1 KCl was investigated. Ni foam and Ni hydroxide, which are commonly used in water splitting at extreme pH levels, were unstable, and Co, Fe, and Ti-based materials were found to be the candidates for seawater splitting. Among various combinations of these elements, the CoFeOxHy/TF (Ti felt) electrode showed better performance than CoOxHy/TF and FeOxHy/TF electrodes. The CoFeOxHy electrode possessed a three-hold larger double layer capacitance (C dl) which is the electrochemically active surface area than its counterparts. Our kinetic study revealed that Tafel slopes and apparent activation energies of CoFeOxHy resembled the control CoOxHy and FeOxHy electrodes, indicating that the performance difference was originated from the enlarged surface area caused by mixed Co and Fe.In addition to the development of electrocatalysts, electrolyte engineering plays a key role. By employing the CoFeOxHy/TF electrode, the OER performance was investigated in varied molality and counter cation borate electrolytes at pH 9.2. The molarity of K-borate above 1.0 mol kg− 1 was found to be essential to minimize the concentration overpotential, which helps to maintain the electrode potential below the thermodynamic window of COR. The OER performance was insensitive to cation identity except for the Na cation counterpart having a low solubility product. Furthermore, Cl−-containing electrolyte had a higher conductivity than that without Cl−, which can be an advantage to decrease the ohmic resistance in two electrode configurations for future application.The influence of the potential window on the stability and selectivity was investigated by using the developed electrode and 1.0 mol kg−1 K-borate (pH 9.2) with 0.5 mol kg−1 KCl. Below the redox potential of ClO− formation at 1.72 VRHE (V vs. Reversible hydrogen electrode), current density-potential relationships were insensitive to the Cl−. At 1.72 VRHE in the presence of Cl−, the faradaic efficiency (FE) of O2 (FEO2) reached 98±1%, whereas the FE of hypochlorite (FEHC) was merely 1±1%. Above this threshold potential, under chronopotentiometry (CP) testing at 50 mA cm−2 corresponding to approximately 1.82 VRHE, FEO2 decreased to 93±2% and FEHC increased to 7±2%. Critically, the potential of 1.82 VRHE was larger than 1.78 VRHE observed without Cl−, likely due to the blockage of the OER active site by Cl− or related species. Finally, aiming for the practical application, the OER performance over CoFeOxHy was examined at 353 K. The FEO2 reached 99±2% at 500 mA cm− 2 and 1.67 VRHE (Figure 1). Our calculations on thermodynamics revealed that the redox potential of OER decreases to 1.18 VRHE while that of ClO− formation reaction is 1.71 VRHE at 353 K, leaving a potential gap of 530 mV. High selectivity toward the OER was attributed to the consequence of fine engineering of electrocatalysts and electrolytes that successfully maintained the potential below the 1.71 VRHE where the OER is thermodynamically dominant. In addition, the electrode was stable for multiple on-off accelerated stability testing for 10 h at 500 mA cm− 2 and 353 K.Reference[1] S. Dresp, F. Dionigi, M. Klingenhof, P. Strasser, ACS Energy Lett. 2019, 4, 933–942.[2] C. J. Vörösmarty, P. B. McIntyre, M. O. Gessner, D. Dudgeon, A. Prusevich, P. Green, S. Glidden, S. E. Bunn, C. A. Sullivan, C. R. Liermann, Nature 2010, 467, 555–561.[3] J. G. Vos, M. T. M. Koper, J. Electroanal. Chem. 2018, 819, 260–268. Figure 1

Computational study of the adamantane cation: simulations of spectroscopy, fragmentation dynamics, and internal conversion

Diamondoids, of which adamantane (C_{10}H_{16}) is the simplest representative, constitute an intriguing class of carbon based nanomaterials with interesting chemical, mechanical and opto-electronic properties. While neutral diamondoids have been extensively studied for decades, their cationic counterparts were a subject of recent experimental investigations motivated by their potential role in astrochemistry. Here, we perform a computational study of the adamantane cation (C_{10}H_{16}^+) complementing the recent experimental findings. Specifically, we extend earlier theoretical work on vibrationally resolved electronic spectroscopy by accounting for the higher lying electronically excited states of the cation in the absorption and photoelectron spectra. We also perform adiabatic and nonadiabatic (surface hopping) molecular dynamics simulations to study (fast) fragmentation processes and electronic relaxation of C_{10}H_{16}^+. Our simulations reveal that after excitation with near-infrared–ultraviolet photons, the adamantane cation undergoes an ultrafast internal conversion to the ground (doublet) state (on a time scale of 10–100 fs depending on initial excitation energy) which can be followed by a fast fragmentation, predominantly H loss. The yield of the ultrafast hydrogen dissociation as a function of excitation energy is reported.

Does the Sign of Charge Affect the Surface Affinity of Simple Ions?

The role the charge sign of simple ions plays in determining their surface affinity in aqueous solutions is investigated by computer simulation methods. For this purpose, the free surface of aqueous solutions of fictitious salts is simulated at finite concentration both with nonpolarizable point-charge and polarizable Gaussian-charge potential models. The salts consist of monovalent cations and anions that are, apart from the sign of their charge, identical to each other. In particular, we consider the small Na+ and the large I- ions together with their charge-inverted counterparts. In an attempt to avoid the interference even between the behavior of cations and anions, we also simulate systems containing only one of the above ions, and determine the free energy profile of these ions across the liquid-vapor interface of water at infinite dilution by potential of mean force (PMF) calculations. The obtained results reveal that, in the case of small ions, the anion is hydrated considerably stronger than the cation due to the close approach of water H atoms, bearing a positive fractional charge. As a consequence, the surface affinity of a small anion is even smaller than that of its cationic counterpart. However, considering that small ions are effectively repelled from the water surface, the importance of this difference is negligible. Further, a change in the hydration energy trends of the two oppositely charged ions is observed with their increasing size. This change is largely attributed to the fact that, with increasing ion size, the factor of 2 in the magnitude of the fractional charge of the closely approaching water atoms (i.e., O around cations and H around anions) outweighs the closer approach of the H than the O atom in the hydration energy. Thus, for large ions, being already surface active themselves, the surface affinity of the anion is larger than that of its positively charged counterpart. Further, such a difference is seen even in the case when the sign of the surface potential favors the adsorption of cations.

Luminescent Zirconocene Complexes with Pendant Phosphine Chalcogenide Donor Groups

Neutral zirconocene complexes of the type [(η5-C5Me5){η5-C5H4CMe2P(═E)Ph2}ZrCl2] (E = not present, O, S, or Se) with a cyclopentadienyl-attached phosphine and related phosphine oxide, sulfide, or selenide moiety were prepared and converted to their cationic counterparts by chloride abstraction with K[B(C6F5)4] to give compounds of the general formula [(η5-C5Me5){η5-C5H4CMe2P(═E)Ph2-κE}ZrCl]+[B(C6F5)4]−. Alternatively, the chloride abstraction was accomplished by the reaction with ZnCl2 to give the same cationic species with a [Zn2Cl6]2– counteranion. The ionic complexes, unlike the neutral counterparts, exhibited strongly enhanced luminescence properties originating in triplet ligand-to-metal (3LMCT) excited states. Luminescence quantum yields up to 0.95 were determined in the solid state with luminescence lifetimes up to 50.6 μs. In addition to structural characterization of the prepared complexes by X-ray diffraction methods, their electrochemistry was investigated by cyclic voltammetry, and their photophysical properties were studied with quantum-chemical calculations.

Stabilization of calcareous subgrade soils with polyelectrolytes: mechanisms and mechanical properties

ABSTRACT Organic polyelectrolytes, i.e. anionic poly(sodium 4-styrenesulphonate) (PSS), cationic poly(diallyldimethylammonium chloride) (PDADMAC) and their polyelectrolyte complexes (PECs) were evaluated for stabilisation of calcareous sandy subgrade soil. This paper investigated the effects of polymer type, surface charge type of PEC, concentrations of PEC solutions and dosages of polymer solutions added to the soil on improvement of soil mechanical properties. We found that anionic polymers, for both PECs and individual polyelectrolytes, were superior to their cationic counterparts in improving soil strength. Besides, the constituent polyelectrolytes, PSS and PDADMAC, worked better than their PECs for the specific soil investigated. The strength of polymer-treated soils was also found to increase with the increase in dosages of the polymer solutions as well as curing periods. Furthermore, polymer-treated soil specimens exhibited significant toughness improvement, which was higher than cement-treated samples. Scanning electron microscopy images revealed the abundance of long palygorskite fibres covering the surfaces of larger calcite and dolomite particles and linking surrounding aggregates after adding polymers. This observation suggests the interconnection of palygorskite fibres and their linking networks between and among coarse aggregates as the likely mechanism of polymer stabilisation of the soil studied.

A vibrational action spectroscopic study of the Renner-Teller- and spin-orbit-affected cyanoacetylene radical cation HC3N.

The linear radical cation of cyanoacetylene, HC3N+ (2Π), is not only of astrophysical interest, being the, so far undetected, cationic counterpart of the abundant cyanoaceteylene, but also of fundamental spectroscopic interest due to its strong spin-orbit and Renner-Teller interactions. Here, we present the first broadband vibrational action spectroscopic investigation of this ion through the infrared pre-dissociation (IRPD) method using a Ne tag. Experiments have been performed using the FELion cryogenic ion-trap instrument in combination with the FELIX free-electron lasers and a Laservision optical parametric oscillator/optical parametric amplifier system. The vibronic splitting patterns of the three interacting bending modes (ν5, ν6, ν7), ranging from 180to1600 cm-1, could be fully resolved revealing several bands that were previously unobserved. The associated Renner-Teller and intermode coupling constants have been determined by fitting an effective Hamiltonian to the experimental data, and the obtained spectroscopic constants are in reasonable agreement with previous photoelectron spectroscopy (PES) studies and ab initio calculations on the HC3N+ ion. The influence of the attached Ne atom on the infrared spectrum has been investigated by ab initio calculations at the RCCSD(T)-F12a level of theory, which strongly indicates that the discrepancies between the IRPD and PES data are a result of the effects of the Ne attachment.

Structural, physicochemical and anticancer study of Zn complexes with pyridyl-based thiazolyl-hydrazones

Thiazolyl-hydrazones (THs) exhibit a wide spectrum of biological activity that can be enhanced by complexation with various metal ions. Zn(II) complexes with α-pyridine-1,3-TH ligands may represent an alternative to the standard platinum-based chemotherapeutics. In addition, they show photoluminescence properties and thus can be regarded as multifunctional materials. In this study, we synthesized and characterized three neutral Zn(II) complexes (1–3) with pyridine-based TH ligands HLS1‒3 in order to investigate the influence of the ligands charge on the structure and intermolecular interactions in the solid state, and consequently photophysical properties. The deprotonation of the ligands mainly affects the relative energies of electronic levels in the complexes, compared to cationic counterparts, resulting in similar photoluminescence mechanisms and quantum yields with a small shift in emission energy. The influence of the substitution at the ligands’ periphery on the selected quantum molecular descriptors of the complexes is localized to the substitution site. Also, the substituents did not considerably influence the redox responses of the complexes. However, predominant spectral changes were observed in the course of the first reduction and oxidation processes which caused distinct spectral color changes indicating their possible functionality for electrochromic applications. In addition, complex 1 showed antiproliferative activity with GI50 values below 2 µM on all tested cancer cell lines.

Crystal Engineering of Cation-Radical Salts with Weakly Coordinating Carbadodecaborate Anions

An X-ray structural analysis revealed that the salts of N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), N-methylphenothiazine (MPTZ), and octamethylbiphenylene (OMB), with dodecamethyl- or hexabromo-substituted carbadodecaborate anions, comprise layers of the (partially) oxidized organic donors separated by sheets of the bulky counter-ions. The cationic layers comprise either well-separated TMPD+ or MPTZ+ cation radicals or π-stacks of partially oxidized OMB moieties consisting of more or less distinct (OMB)2+ units. Quantum mechanical calculations revealed that the formation of essentially isolated cation-radical or π-bonded associations in the salts with these weakly coordinating anions is correlated with the strength of the multicenter π-bonding between cation radicals. This pancake bonding is determined by the balance of the electrostatic repulsion between cationic counterparts and attractive dispersion and weakly covalent interactions.

Refining the thermochemical properties of CF, SiF, and their cations by combining photoelectron spectroscopy, quantum chemical calculations, and the Active Thermochemical Tables approach.

Fluorinated species have a pivotal role in semiconductor material chemistry and some of them have been detected beyond the Earth's atmosphere. Achieving good energy accuracy on fluorinated species using quantum chemical calculations has long been a challenge. In addition, obtaining direct experimental thermochemical quantities has also proved difficult. Here, we report the threshold photoelectron and photoion yield spectra of SiF and CF radicals generated with a fluorine reactor. The spectra were analysed with the support of ab initio calculations, resulting in new experimental values for the adiabatic ionisation energies of both CF (9.128 ± 0.006 eV) and SiF (7.379 ± 0.009 eV). Using these values, the underlying thermochemical network of Active Thermochemical Tables was updated, providing further refined enthalpies of formation and dissociation energies of CF, SiF, and their cationic counterparts.

Encapsulation of Gold-Based Anticancer Agents in Protease-Degradable Peptide Nanofilaments Enhances Their Potency.

We investigated the use of amphiphilic, protease-cleavable peptides as encapsulation moieties for hydrophobic metallodrugs, in order to enhance their bioavailability and consequent activity. Two hydrophobic, gold-containing anticancer agents varying in aromatic ligand distribution (Au(I)-N-heterocyclic carbene compounds 1 and 2) were investigated. These were encapsulated into amphiphilic decapeptides that form soluble filamentous structures with hydrophobic cores, varying supramolecular packing arrangements and surface charge. Peptide sequence strongly dictates the supramolecular packing within the aromatic core, which in turn dictates drug loading. Anionic peptide filaments can effectively load 1, and to a lesser extent 2, while their cationic counterparts could not, collectively demonstrating that loading efficiency is dictated by both aromatic and electrostatic (mis)matching between drug and peptide. Peptide nanofilaments were nontoxic to cancerous and noncancerous cells. By contrast, those loaded with 1 and 2 displayed enhanced cytotoxicity in comparison to 1 and 2 alone, when exposed to Caki-1 and MDA-MB-231 cancerous cell lines, while no cytotoxicity was observed in noncancerous lung fibroblasts, IMR-90. We propose that the enhanced in vitro activity results from the enhanced proteolytic activity in the vicinity of the cancer cells, thereby breaking the filaments into drug-bound peptide fragments that are taken up by these cells, resulting in enhanced cytotoxicity toward cancer cells.

Exploration of Dual Ionic Cross-Linked Alginate Hydrogels Via Cations of Varying Valences towards Wound Healing

This study explored the synergistic effects of simultaneously using calcium and gallium cations in the cross-linking of alginate, detailing its effects on the characteristics of alginate compared to its single cation counterparts. The primary goal is to determine if there are any synergistic effects associated with the utilisation of multiple multivalent cations in polymer cross-linking and whether or not it could therefore be used in pharmaceutical applications such as wound healing. Given the fact divalent and trivalent cations have never been utilised together for cross-linking, an explanation for the mode of binding that occurs between the alginate and the cations during the cross-linking process and how it may affect the future applications of the polymer has been investigated. The calcium gallium alginate polymers were able to retain the antibacterial effects of gallium within the confines of the polymer matrix, possessing superior rheological properties, 6 times that of pure calcium and pure gallium, coupled with an improved swelling capacity that is 4 times higher than that of gallium alginate.

Single-cell scanning photoelectrochemical microscopy using micro-optical-ring electrodes

Microelectrodes as analytical sensing tools have gained immense popularity in a wide range of applications, ranging from probe design advancement to single live cell imaging. Micro-optical-ring electrodes (MOREs) are micro-scale ring-electrodes with an optical fiber core, that enables the MORE to conduct an optical signal while performing electrochemistry. Herein, we present a user-friendly and cost-effective method to fabricate MOREs for scanning photoelectrochemical microscopy (SPECM) applications. MOREs were characterized by electrochemistry, numerical modelling, and scanning electron microscopy (SEM), ensuring reproducibility in terms of a well-defined geometry and functionality. In this study, the integration of MOREs into scanning probe microscopy enabled the spectro-electrochemical detection of N, N, N, N′- Tetramethyl-p-phenyl-enediamine (TMPD) and its oxidized radical cation counterpart. UV-VIS spectroscopy capabilities of MOREs were optimized through tip-to-substrate distance variations. To demonstrate the applicability of MOREs to electrochemical single live cell imaging, oxygen production was detected in living algae (Eremosphaera viridis) by local illumination and concurrent electrochemical measurements.

Synthesis of a low-valent Al4+ cluster cation salt.

Low-valent aluminium compounds are very reactive main-group species and have therefore been widely investigated. Since the isolation of a stable molecular Al(I) compound in 1991, [(AlCp*)4] (Cp* = [C5Me5]-), a variety of highly reactive neutral or anionic low-valent aluminium complexes have been developed. By contrast, their cationic counterparts have remained difficult to access. Here, we report the synthesis of [Al(AlCp*)3]+[Al(ORF)4]- (RF = C(CF3)3) through a simple metathesis reaction between [(AlCp*)4] and Li[Al(ORF)4]. Unexpectedly, the [Al(AlCp*)3]+ salt forms a dimer in the solid state and concentrated solutions. Addition of Lewis bases results in monomerization and coordination to the unique formal Al+ atom, giving [(L)xAl(AlCp*)3]+ salts where L is hexaphenylcarbodiphosphorane (x = 1), tetramethylethylenediamine (x = 1) or 4-dimethylaminopyridine (x = 3). The Al+-AlCp* bonds in the resulting [(L)xAl(AlCp*)3]+ cluster cations can be finely tuned between very strong (with no ligand L) to very weak and approaching isolated [Al(L)3]+ ions (when L is dimethylaminopyridine).

Synthesis, photophysical, electrochemical and computational investigation of dimethine and trimethine cyanine-based dyes

Three novel cyanine-based dyes (D1-D3) were obtained by the carboxylic indolium salt the condensation reaction with three different donors, N,N-dimethylaniline, carbazole and indole derivatives. The chemical structures of these dyes were confirmed and fully characterized by IR, NMR, and HRMS. The UV–vis, fluorescence spectra, and cyclic voltammetry were conducted to give a preliminary insight into their optoelectronic properties. Generally, all synthesized dyes exhibited well-defined absorption in the visible region with high absorptivity and low band gap, giving λEx. max (516–564 nm), ε (45279–141011 M−1cm−1) and E0-0 (2.11–2.21 eV). Distinctive stokes shifts were observed for all dyes, with the highest value for the dimethine cyanine containing carbazole donor, D2, (2752 cm−1). The solvatochromic study showed hypsochromic effects and increased Stokes shifts with increasing solvent polarity. The electrochemical study on the other hand revealed having HOMO and LUMO energy levels, <-5.46, and > -3.58 eV, respectively, indicating their suitability as sensitizers in dye sensitized solar cells. The impact of different donors on the geometrical, photophysical, charge transfer and reorganization energy on the designed dyes has been investigated using Density Functional Theory (DFT) and time-dependent (TD-DFT). The theoretical and experimental results are in good agreement. The results indicate that the D1-D3 dyes have a small energy gap (2.50–2.77 eV) and their cationic counterpart absorption in the visible (480–576 nm). The modification of the donor suggests that these dyes would be suitable for dye-sensitized solar cells (DSCCs).

Machine Learning Quantitative Structure-Property Relationships as a Function of Ionic Liquid Cations for the Gas-Ionic Liquid Partition Coefficient of Hydrocarbons.

Ionic liquids (ILs) are known for their unique characteristics as solvents and electrolytes. Therefore, new ILs are being developed and adapted as innovative chemical environments for different applications in which their properties need to be understood on a molecular level. Computational data-driven methods provide means for understanding of properties at molecular level, and quantitative structure–property relationships (QSPRs) provide the framework for this. This framework is commonly used to study the properties of molecules in ILs as an environment. The opposite situation where the property is considered as a function of the ionic liquid does not exist. The aim of the present study was to supplement this perspective with new knowledge and to develop QSPRs that would allow the understanding of molecular interactions in ionic liquids based on the structure of the cationic moiety. A wide range of applications in electrochemistry, separation and extraction chemistry depends on the partitioning of solutes between the ionic liquid and the surrounding environment that is characterized by the gas-ionic liquid partition coefficient. To model this property as a function of the structure of a cationic counterpart, a series of ionic liquids was selected with a common bis-(trifluoromethylsulfonyl)-imide anion, [Tf2N]−, for benzene, hexane and cyclohexane. MLR, SVR and GPR machine learning approaches were used to derive data-driven models and their performance was compared. The cross-validation coefficients of determination in the range 0.71–0.93 along with other performance statistics indicated a strong accuracy of models for all data series and machine learning methods. The analysis and interpretation of descriptors revealed that generally higher lipophilicity and dispersion interaction capability, and lower polarity in the cations induces a higher partition coefficient for benzene, hexane, cyclohexane and hydrocarbons in general. The applicability domain analysis of models concluded that there were no highly influential outliers and the models are applicable to a wide selection of cation families with variable size, polarity and aliphatic or aromatic nature.