Synthesis, Characterization, and Structural Analysis of AM[Al(NONDipp)(H)(SiH2Ph)] (AM = Li, Na, K, Rb, Cs) Compounds, Made Via Oxidative Addition of Phenylsilane to Alkali Metal Aluminyls.

We report the oxidative addition of phenylsilane to the complete series of alkali metal (AM) aluminyls [AM{Al(NONDipp)}]2 (AM = Li, Na, K, Rb, and Cs). Crystalline products (1-AM) have been isolated as ether or THF adducts, [AM(L)n][Al(NONDipp)(H)(SiH2Ph)] (AM = Li, Na, K, Rb, L = Et2O, n = 1; AM = Cs, L = THF, n = 2). Further to this series, the novel rubidium rubidiate, [{Rb(THF)4}2(Rb{Al(NONDipp)(H)(SiH2Ph)}2)]+ [Rb{Al(NONDipp)(H)(SiH2Ph)}2]-, was isolated during an attempted recrystallization of Rb[Al(NONDipp)(H)(SiH2Ph)] from a hexane/THF mixture. Structural and spectroscopic characterizations of the series 1-AM confirm the presence of µ-hydrides that bridge the aluminum and alkali metals (AM), with multiple stabilizing AM···π(arene) interactions to either the Dipp- or Ph-substituents. These products form a complete series of soluble, alkali metal (hydrido) aluminates that present a platform for further reactivity studies.

Ru(II)/amino acid complexes inhibit the progression of breast cancer cells through multiple mechanism-induced apoptosis.

For some cancer subtypes, such as triple-negative breast cancer, there are no specific therapies, which leads to a poor prognosis associated with invasion and metastases. Ruthenium complexes have been developed to act in all steps of tumor growth and its progression. In this study, we investigated the effects of Ruthenium (II) complexes coupled to the amino acids methionine (RuMet) and tryptophan (RuTrp) on the induction of cell death, clonogenic survival ability, inhibition of angiogenesis, and migration of MDA-MB-231 cells (human triple-negative breast cancer). The study also demonstrated that the RuMet and RuTrp complexes induce cell cycle blockage and apoptosis of MDA-MB-231 cells, as evidenced by an increase in the number of Annexin V-positive cells, p53 phosphorylation, caspase 3 activation, and poly(ADP-ribose) polymerase cleavage. Moreover, morphological changes and loss of mitochondrial membrane potential were detected. The RuMet and RuTrp complexes induced DNA damage probably due to reactive oxygen species production related to mitochondrial membrane depolarization. Therefore, the RuMet and RuTrp complexes acted directly on breast tumor cells, leading to cell death and inhibiting their metastatic potential; this reveals the potential therapeutic action of these drugs.

Investigating Rubidium Density and Temperature Distributions in a High-Throughput 129Xe-Rb Spin-Exchange Optical Pumping Polarizer.

Accurate knowledge of the rubidium (Rb) vapor density, [Rb], is necessary to correctly model the spin dynamics of 129Xe-Rb spin-exchange optical pumping (SEOP). Here we present a systematic evaluation of [Rb] within a high-throughput 129Xe-Rb hyperpolarizer during continuous-flow SEOP. Near-infrared (52S1/2→52P1/2 (D1)/52P3/2 (D2)) and violet (52S1/2→62P1/2/62P3/2) atomic absorption spectroscopy was used to measure [Rb] within 3.5 L cylindrical SEOP cells containing different spatial distributions and amounts of Rb metal. We were able to quantify deviation from the Beer-Lambert law at high optical depth for D2 and 62P3/2 absorption by comparison with measurements of the D1 and 62P1/2 absorption lines, respectively. D2 absorption deviates from the Beer-Lambert law at [Rb]D2>4×1017 m−3 whilst 52S1/2→62P3/2 absorption deviates from the Beer-Lambert law at [Rb]6P3/2>(4.16±0.01)×1019 m−3. The measured [Rb] was used to estimate a 129Xe-Rb spin exchange cross section of γ'=(1.2±0.1)×10−21 m3 s−1, consistent with spin-exchange cross sections from the literature. Significant [Rb] heterogeneity was observed in a SEOP cell containing 1 g of Rb localized at the back of the cell. While [Rb] homogeneity was improved for a greater surface area of the Rb source distribution in the cell, or by using a Rb presaturator, the measured [Rb] was consistently lower than that predicted by saturation Rb vapor density curves. Efforts to optimize [Rb] and thermal management within spin polarizer systems are necessary to maximize potential future enhancements of this technology.

Development of porous material via chitosan-based Pickering medium internal phase emulsion for efficient adsorption of Rb+, Cs+ and Sr2.

The radioactive Rb+, Cs+ and Sr2+ have serious threat for the aquatic life and human health, its removal has been granted increasing concern. Hence the adsorbent with excellent adsorption performance and favourable reusability is strongly demanded. This work prepared a novel porous polymer of chitosan-g-polyacrylamide (CTS-g-PAM) by grafting the acrylamide (AM) onto the chitosan (CTS) with sufficient pore structure via an eco-friendly surfactant-free (corn oil)-in-water Pickering medium internal phase emulsion (O/W Pickering MIPE), solely stabilized by CTS. Interestingly, its pore structure could be tuned by varying the emulsion character via changing the molecular weight and concentration of CTS, as well as the pH values. Due to the abundant -COO- and -NH2 functional groups in the porous material of CTS-g-PAM, the high adsorption capacities of 195.43, 237.44 and 185.63 mg/g for Rb+, Cs+ and Sr2+ could be reached within 40, 30 and 20 min, respectively. Moreover, the CTS-g-PAM had excellent regeneration ability and reusability. Herein, we provided a feasible and low-cost pathway for preparation of the porous adsorbent with tunable porous structure for adsorption and separation application.

C-H Activation by RuCo3O4 Oxo Cubanes: Effects of Oxyl Radical Character and Metal-Metal Cooperativity.

High-valent multimetallic-oxo/oxyl species have been implicated as intermediates in oxidative catalysis involving proton-coupled electron transfer (PCET) reactions, but the reactive nature of these oxo species has hindered the development of an in-depth understanding of their mechanisms and multimetallic character. The mechanism of C-H oxidation by previously reported RuCo3O4 cubane complexes bearing a terminal RuV-oxo ligand, with significant oxyl radical character, was investigated. The rate-determining step involves H atom abstraction (HAA) from an organic substrate to generate a Ru-OH species and a carbon-centered radical. Radical intermediates are subsequently trapped by another equivalent of the terminal oxo to afford isolable radical-trapped cubane complexes. Density functional theory (DFT) reveals a barrierless radical combination step that is more favorable than an oxygen-rebound mechanism by 12.3 kcal mol-1. This HAA reactivity to generate organic products is influenced by steric congestion and the C-H bond dissociation energy of the substrate. Tuning the electronic properties of the cubane (i.e., spin density localized on terminal oxo, basicity, and redox potential) by varying the donor ability of ligands at the Co sites modulates C-H activations by the RuV-oxo fragment and enables construction of structure-activity relationships. These results reveal a mechanistic pathway for C-H activation by high-valent metal-oxo species with oxyl radical character and provide insights into cooperative effects of multimetallic centers in tuning PCET reactivity.

Surprising Condensation Reactions of the Azadithiolate Cofactor.

Azadithiolate, a cofactor found in all [FeFe]-hydrogenases, is shown to undergo acid-catalyzed rearrangement. Fe2 [(SCH2 )2 NH](CO)6 self-condenses to give Fe6 [(SCH2 )3 N]2 (CO)17 . The reaction, which is driven by loss of NH4+ , illustrates the exchange of the amine group. X-ray crystallography reveals that three Fe2 (SR)2 (CO)x butterfly subunits interconnected by the aminotrithiolate [N(CH2 S)3 ]3- . Mechanistic studies reveal that Fe2 [(SCH2 )2 NR](CO)6 participate in a range of amine exchange reactions, enabling new methodologies for modifying the adt cofactor. Ru2 [(SCH2 )2 NH](CO)6 also rearranges, but proceeds further to give derivatives with Ru-alkyl bonds Ru6 [(SCH2 )3 N][(SCH2 )2 NCH2 ]S(CO)17 and [Ru2 [(SCH2 )2 NCH2 ](CO)5 ]2 S.

Investigation of the Effects and Mechanisms of Anticancer Action of a Ru(II)-Arene Iminophosphorane Compound in Triple Negative Breast Cancer Cells.

Triple negative breast cancer (TNBC) is one of the breast cancers with poorer prognosis and survival rates. TNBC has a disproportionally high incidence and mortality in women of African descent. We report on the evaluation of Ru-IM (1), a water-soluble organometallic ruthenium compound, in TNBC cell lines derived from patients of European (MDA-MB-231) and African (HCC-1806) ancestry (including IC50 values, cellular and organelle uptake, cell death pathways, cell cycle, effects on migration, invasion, and angiogenesis, a preliminary proteomic analysis, and an NCI 60 cell-line panel screen). 1 was previously found highly efficacious in MDA-MB-231 cells and xenografts, with little systemic toxicity and preferential accumulation in the tumor. We observe a similar profile for this compound in the two cell lines studied, which includes high cytotoxicity, apoptotic behavior and potential antimetastatic and antiangiogenic properties. Cytokine M-CSF, involved in the PI3/AKT pathway, shows protein expression inhibition with exposure to 1. We also demonstrate a p53 independent mechanism of action.

Sodium cationization can disrupt the intramolecular hydrogen bond that mediates the sunscreen activity of oxybenzone.

A key decay pathway by which organic sunscreen molecules dissipate harmful UV energy involves excited-state hydrogen atom transfer between proximal enol and keto functional groups. Structural modifications of this molecular architecture have the potential to block ultrafast decay processes, and hence promote direct excited-state molecular dissociation, profoundly affecting the efficiency of an organic sunscreen. Herein, we investigate the binding of alkali metal cations to a prototype organic sunscreen molecule, oxybenzone, using IR characterization. Mass-selective IR action spectroscopy was conducted at the free electron laser for infrared experiments, FELIX (600-1800 cm-1), on complexes of Na+, K+ and Rb+ bound to oxybenzone. The IR spectra reveal that K+ and Rb+ adopt binding positions away from the key OH intermolecular hydrogen bond, while the smaller Na+ cation binds directly between the keto and enol oxygens, thus breaking the intramolecular hydrogen bond. UV laser photodissociation spectroscopy was also performed on the series of complexes, with the Na+ complex displaying a distinctive electronic spectrum compared to those of K+ and Rb+, in line with the IR spectroscopy results. TD-DFT calculations reveal that the origin of the changes in the electronic spectra can be linked to rupture of the intramolecular bond in the sodium cationized complex. The implications of our results for the performance of sunscreens in mixtures and environments with high concentrations of metal cations are discussed.

A density functional theory study on the interaction of toluene with transition metal decorated carbon nanotubes: a promising platform for early detection of lung cancer from human breath.

In this study, single-wall carbon nanotubes (SWCNTs) decorated by platinum-group transition metals (Pt, Pd, Rh, or Ru) were introduced as promising nanosensors for the detection of toluene, an important biomarker in the exhaled breath of the lung cancer patients. First-principle calculations based on density functional theory (DFT) was employed to scrutinize the impact of an individual toluene gas molecule on the structural, electronic, and magnetic properties of pristine and metal decorated SWCNTs. It was discovered that toluene is physisorbed on the pristine SWCNT through the interaction of the π orbitals of the carbon atoms in the toluene and the nanotube. Decoration of the SWCNT with metal atoms enhanced the adsorption energies significantly by means of strong overlapping between d orbital of the metal atoms and p orbital of C atoms in the benzene ring of toluene. Investigations showed that toluene is strongly chemisorbed on Rh- and Ru-SWCNT systems via strong covalent bonds with the superior response (-96.98% and -99.98%, respectively), and moderately chemisorbed on Pt-SWCNTs (-27.3%) and Pd-SWCNTs (61.60%). Our findings propose metal decorated SWCNT molecular sensors are attractive candidates for the detection of toluene and other lung cancer biomarkers in the exhaled breath of the lung cancer patients.

Light-activated gold nanorod vesicles with NIR-II fluorescence and photoacoustic imaging performances for cancer theranostics.

Fluorescence (FL) and photoacoustic (PA) imaging in the second near infrared window (NIR-II FL and NIR-II PA) hold great promise for biomedical applications because of their non-invasive nature and excellent spatial resolution properties. Methods: We develop a NIR-II PA and NIR-II FL dual-mode imaging gold nanorod vesicles (AuNR Ves) by self-assembly of amphiphilic AuNR coated with light responsive polyprodrug of Ru-complex and PEG, and NIR-II cyanine dye (IR 1061). The AuNR Ves showed strong ligh absorption property and PA imaging performance in the NIR-II windows. Moreover, the NIR-II fluorescence signal of IR 1061 loaded in the AuNR Ve is quenched. Results: The AuNR Ves can release photosensitizer Ru-complex and IR 1061 sequentially triggered by NIR light irradiation, leading to a corresponding NIR-II PA signal decrease and NIR-II FL signal recovery. Meanwhile, Ru-complex can not only serve as a chemotherapeutic drug but also generate singlet oxygen (1O2) under NIR light irradiation. The release of Ru-complex and photodynamic therapy are guided by the responsive variation of NIR-II PA and NIR-II FL signals. Conclusions: The AuNR Ve possessing not only precisely control 1O2/drug release but also the intrinsic ability to monitor therapy process offers a new strategy for the development of smart theranostic nanoplatform.

Periodic Tendril Perversion and Helices in the AMoO2F3 (A = K, Rb, NH4, Tl) Family.

Although compounds of the formula AMoO2F3 (A = K, Rb, Cs, NH4, Tl) have been known for decades, crystal structures have only been reported for CsMoO2F3 and NH4MoO2F3. The three compounds (Rb/NH4/Tl)MoO2F3 are isostructural and crystallize in the centrosymmetric space group C2/c (No. 15). The compounds contain the MoO2F3- anionic chain, composed of corner-sharing MoO2F4 octahedra, with Mo6+ coordinated by two cis bridging fluoride anions that are trans to terminal oxide anions. The MoO2F3- chain has a very unusual and complex chain structure; a single chain contains alternating zigzag and helical sections. These helical regions alternate in chirality along the chain, and thus the chains exhibit periodic tendril perversion. To the best of the authors' knowledge, no other materials with a similar chain structure have been reported. On the other hand, KMoO2F3 is noncentrosymmetric and chiral, crystallizing in the enantiomorphic space group P212121 (No. 19). KMoO2F3 also contains the MoO2F3- anionic chain. However, the chain is helical, with only one enantiomer present, resulting in a chiral, noncentrosymmetric structure.

All-Inorganic Copper Halide as a Stable and Self-Absorption-Free X-ray Scintillator.

Lead halide perovskites have recently shown great potential as X-ray scintillators; however, the toxicity of the lead element seriously restricts their applications. Herein we report a new lead-free and self-absorption-free scintillator based on Rb2CuCl3 metal halide. The Rb2CuCl3 exhibits a near-unity photoluminescence quantum yield (99.4%) as well as a long photoluminescence lifetime (11.3 µs). Furthermore, Rb2CuCl3 demonstrates an appreciable light yield of 16 600 photons per megaelectronvolt and a large scintillation response with a linear range from 48.6 nGyair s-1 to 15.7 µGyair s-1. Notably, the detection limit is as low as 88.5 nGyair s-1, enabling a reduced radiation dose to the human body when a medical and security check is conducted. In addition, Rb2CuCl3 exhibits good stability against the atmosphere, continuous ultraviolet light, as well as X-ray irradiation. The combination of the decent scintillation performance, low toxicity and good stability suggests the Rb2CuCl3 could be a possible promising X-ray scintillator.

High Xe density, high photon flux, stopped-flow spin-exchange optical pumping: Simulations versus experiments.

Spin-exchange optical pumping (SEOP) can enhance the NMR sensitivity of noble gases by up to five orders of magnitude at Tesla-strength magnetic fields. SEOP-generated hyperpolarised (HP) 129Xe is a promising contrast agent for lung imaging but an ongoing barrier to widespread clinical usage has been economical production of sufficient quantities with high 129Xe polarisation. Here, the 'standard model' of SEOP, which was previously used in the optimisation of continuous-flow 129Xe polarisers, is modified for validation against two Xe-rich stopped-flow SEOP datasets. We use this model to examine ways to increase HP Xe production efficiency in stopped-flow 129Xe polarisers and provide further insight into the underlying physics of Xe-rich stopped-flow SEOP at high laser fluxes.

Synthesis, crystal structure and leishmanicidal activity of new trimethoprim Ru(III), Cu(II) and Pt(II) metal complexes.

Leishmaniasis is a parasitic disease caused by protozoa of the genus Leishmania, which has very limited treatment options and affects poor and underdeveloped populations. The current treatment is plagued by many complications, such as high toxicity, high cost and resistance to parasites; therefore, novel therapeutic agents are urgently needed. Herein, the synthesis, characterization and in vitro leishmanicidal potential of new complexes with the general formula [RuCl3(TMP)(dppb)] (1), [PtCl(TMP)(PPh3)2]PF6 (2) and [Cu(CH3COO)2(TMP)2]·DMF (3) (dppb = 1,4-bis(diphenylphosphino)butane, PPH3 = triphenylphosphine and TMP = trimethoprim) were evaluated. The complexes were characterized by infrared, UV-vis, cyclic voltammetry, molar conductance measurements, elemental analysis and NMR experiments. Also, the geometry of (2) and (3) were determined by single crystal X-ray diffraction. Despite being less potent against promastigote L. amazonensis proliferation than amphotericin B reference drug (IC50 = 0.09 ± 0.02 µM), complex (2) (IC50 = 3.6 ± 1.5 µM) was several times less cytotoxic (CC50 = 17.8 µM, SI = 4.9) in comparison with amphotericin B (CC50 = 3.3 µM, SI = 36.6) and gentian violet control (CC50 = 0.8 µM). Additionally, complex (2) inhibited J774 macrophage infection and amastigote number by macrophages (IC50 = 6.6 and SI = 2.7). Outstandingly, complex (2) was shown to be a promising candidate for a new leishmanicidal therapeutic agent, considering its biological power combined with low toxicity.

Thermally induced structural metamorphosis of ZnO:Rb nanostructures for antibacterial impacts.

In this work, we report on the synthesis of pure and Rb doped ZnO (ZnO:Rb) nanoparticles by a simple combustion technique followed by thermal treatment in an open-air atmosphere. The prepared samples were characterized using UV-vis spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), photoluminescence, Raman spectroscopy and scanning electron microscopy. The wurtzite hexagonal phase structure of ZnO and a secondary phase of Rb2ZnO2 was observed after doping ZnO with Rb. FTIR and DSC confirmed the functional groups and the thermal stability of the ZnO samples. Field emission scanning electron microscope showed an irregular shaped agglomerated morphology for the ZnO:Rb samples. The chemical states of the undoped and Rb doped samples were identified using X-ray photoelectron spectroscopy for both pure and ZnO:Rb samples. In addition, ZnO:Rb samples exhibit good antimicrobial activities against Bacillus subtilis with a change in antibacterial behaviour as compared to pure ZnO structures indicating their multifunctional applications.

Rubidium analysis as a possible approach for discriminating between Korean and Chinese perilla seeds distributed in Korea.

The aim of this study was to discriminate between Korean and Chinese perilla seeds by using inorganic elemental analysis data combined with orthogonal partial least squares-discriminant analysis (OPLS-DA). Inorganic element content data were obtained from 29 Korean and 11 Chinese perilla seed samples distributed in Korea. Using energy dispersive X-ray fluorescence spectroscopy, 11 species of inorganic elements were detected in the perilla seed samples and eight of them were quantified. The Rb content was selected as the variable to best discriminate between Korean and Chinese perilla seeds using an S-plot generated from OPLS-DA. An accurate range for the Rb content was determined using inductively coupled plasma-optical emission spectroscopy. The Rb content is remarkably higher in Chinese perilla seeds (8.7-19.0 mg/kg) than in Korean perilla seeds (0.0-7.6 mg/kg), thereby suggesting that Rb analysis may be an appropriate approach to discriminate Chinese perilla seeds from Korean perilla seeds.

Intracellular Imaging of Glutathione with MnO2 Nanosheet@Ru(bpy)32+-UiO-66 Nanocomposites.

Fluorescent detection of glutathione (GSH) in the living system has attracted much attention, but current fluorescent probes are usually exposed to the exterior environment, leading to photobleaching and premature leakage and subsequently limiting the sensitivity and photostability. Herein, luminescent metal-organic frameworks [Ru(bpy)32+ encapsulated in UiO-66] coated with manganese dioxide nanosheets [MnO2 NS@Ru(bpy)32+-UiO-66] were prepared by an in situ growth method and further explored to construct a GSH-switched fluorescent sensing platform. Because of the splendid fluorescence quenching ability, special probe leakage blocking role and distinguished recognition of the MnO2 NS, and the improved fluorescence of Ru(bpy)32+ by UiO-66, a low background, highly sensitive and selective detection of GSH with a low limit of detection as 0.28 µM was realized. At the same time, the preparation of MnO2 NS@Ru(bpy)32+-UiO-66 nanocomposites is simple and less toxic, and there was no notable loss of cell survivability after being exposed to MnO2 NS@Ru(bpy)32+-UiO-66 below the concentrations of 120 µg mL-1 for 24 h. Consequently, the results coming from this effort suggest that the new sensing platform will have a great potential in the detection of GSH in living cells.

Antifungal, anticancer, and docking studies of colchiceine complexes with monovalent metal cation salts.

Complexes of colchiceine with monovalent cation perchlorates and iodides have been obtained and characterized by spectroscopic methods. DFT and spectroscopic studies reveal that the dihedral angle ω1-1a-12-12a , crucial for colchicine biological mechanism of action, that is, binding to tubulins depends on the diameter of the complexed metal cation. Biological tests indicated no antifungal properties of colchicine (it was active only toward A.pullulans), in contrast to its derivative-(colchiceine). Complexation of colchiceine with metal cations improved significantly the antifungal potency, even below MIC <1 µg/ml. The colchiceine complexes were more potent than colchiceine, and some of them were even more potent than the fungicidal standard IPBC. The highest potency of colchiceine complexes was noted against A. pullulans (MIC = 0.5 µg/ml). In contrast to the findings concerning antifungal potency, the anticancer studies showed complexes of colchicine more active (~IC50  = 2 nM) than those of colchiceine (~IC50  = 6 µM). MDA-MB-231 breast cancer cell lines and human lung fibroblasts CCD39Lu were also tested.

Divergence of the quadrupole-strain susceptibility of the electronic nematic system YbRu2Ge2.

Ferroquadrupole order associated with local [Formula: see text] atomic orbitals of rare-earth ions is a realization of electronic nematic order. However, there are relatively few examples of intermetallic materials which exhibit continuous ferroquadrupole phase transitions, motivating the search for additional materials that fall into this category. Furthermore, it is not clear a priori whether experimental approaches based on transport measurements which have been successfully used to probe the nematic susceptibility in materials such as the Fe-based superconductors will be as effective in the case of [Formula: see text] intermetallic materials, for which the important electronic degrees of freedom are local rather than itinerant and are consequently less strongly coupled to the charge-carrying quasiparticles near the Fermi energy. In the present work, we demonstrate that the intermetallic compound [Formula: see text] exhibits a tetragonal-to-orthorhombic phase transition consistent with ferroquadrupole order of the Yb ions and go on to show that elastoresistivity measurements can indeed provide a clear window on the diverging nematic susceptibility in this system. This material provides an arena in which to study the causes and consequences of electronic nematicity.

Thermochemical Measurements of Alkali Cation Association to Hexatantalate.

Ion association is an important process in aqueous dissolution, precipitation, and crystallization of ionic inorganic, organic, and biological materials. Polyoxometalates (POMs) are good model compounds for understanding the complex relationships between lattice energy, ion-pairing in solution, and salt solubility. Here we perform calorimetric measurements to elucidate trends in cluster stability, lattice energy, and ion-pairing behavior studies of simple hexatantalate salts in neat water, parent hydroxide solutions, and molybdate melts, extending previous studies on the isostructural hexaniobates. High temperature calorimetry of alkali salts of hexatantalate reveals that the enthalpies of formation from oxides of the K, Rb, and Cs salts are more similar to each other than they are for their niobate analogues and that the tantalate cluster is energetically less stable than hexaniobate. Aqueous dissolution calorimetry reveals that the cesium salt of hexatantalate has a similar concentration dependence on its dissolution enthalpy to that of hexaniobate. However, unlike rubidium hexaniobate, rubidium hexatantalate also exhibits increased concentration dependence, indicating that hextantalate can undergo increased ion-pairing with alkali salts other than cesium, despite the dilute environments studied. Dissolution enthalpies of POM salts in the parent alkali hydroxides shows that protonation of clusters stabilizes lattices even more than the strongly associating heavy alkali cations do. Additionally, neither weak nor strong lattice ion associations necessarily correlates with respectively high or low aqueous solubility. These studies illuminate the importance of considering ion-pairing among the interrelated processes in the aqueous dissolution of ionic salts that can be extended to serving as a model of cation association to metal oxide surfaces.