Bimetallic Species Research Articles

Triel tris(aminoaryl)aluminum, gallium, and indium complexes and their homocoupling reactions mediated by NiBr2

Here, we present the synthesis, spectroscopic characterization, structural analysis, and studies on the bonding situation of group 13 tris(o-aminoaryl) complexes, [M(C6H4(o-NMe2))3] (1–3) and [M(C10H6(o-NMe2))3] (4–6) where M = Al, Ga, In. X-ray and DFT structural parameters, in conjunction with the inspection of the molecular electrostatic potential (MEP) of related triaryl, MAr3, models where Ar = C6H4, C10H6, suggest for 1–6 the presence of two partially polar covalent intramolecular M–N triel bonds. Interestingly, indium complexes 3 and 6 bind a third nitrogen atom with a Van der Waals type interaction. Stoichiometrical reactions of 1–3 with NiBr2 at 25 °C afforded the homocoupling product bi-o-dimethylaminophenyl (7) in up to 73 % isolated yield with 1 and 3 as the nucleophile. While 4–6 performed poorly under the same reaction conditions or at 100 °C providing either traces or at most 13 % of bi-o-dimethylaminonaphtyl (8) with 4 according to GC–MS. Hypothetical DFT bimetallic species [BrNi(μ-Br)M{C6H4(o-NMe2)}3] and [Ni(Br)2M{C10H6(o-NMe2}3] where M = Al (9, 12), Ga (10, 13), In (11, 14) are proposed reaction intermediates implied in the transmetalation/reductive elimination process that affords diaromatic amines 7 and 8.

Enhancement of higher alcohols selectivity in Fischer-Tropsch synthesis using Walnut and Almond shell derived biochars as Copper/Cobalt catalyst support

The production of higher alcohols from synthesis gas using biochar-supported copper-cobalt catalysts is investigated. Biochars were prepared via pyrolysis of Walnut shells and Almond shells and were subsequently activated through physical and chemical methods. A 15 wt% Copper and 5 wt% Cobalt was loaded on the activated biochars via the impregnation technique. The chemical and physical properties of the catalysts were studied using various methods. The catalytic performance of the catalysts was assessed in a fixed-bed microreactor at 20 bars, 320 °C, and, an H2/CO ratio of 2, and the results were compared with the γ-Alumina supported catalyst. Strong interaction between cobalt and copper particles and the formation of bimetallic CuCo2O4 species were observed. The catalysts' reducibility was enhanced by a factor of 1.42. The catalytic studies revealed a significant enhancement in the rate of carbon monoxide hydrogenation. The catalyst supported on low-cost Almond shell-derived biochar demonstrated the best performance. The total alcohol selectivity increased from 22.2 wt% to 34.2 wt%, and the C2+ alcohol selectivity rose from 78.3 wt% to 91.1 wt%, as compared to the industrial catalyst supported on alumina. However, the selectivity for C5+ liquid hydrocarbons decreased to 16.8 wt%. Notably, biochar-supported catalysts also exhibited good stability.

Accessing Ta/Cu Architectures via Metal‐Metal Salt Metatheses: Heterobimetallic C−H Bond Activation Affords μ‐Hydrides

AbstractWe employ a metal‐metal salt metathesis strategy to access low‐valent tantalum‐copper heterometallic architectures (Ta−μ2‐H2−Cu and Ta−μ3‐H2−Cu3) that emulate structural elements proposed for surface alloyed nanomaterials. Whereas cluster assembly with carbonylmetalates is well precedented, the use of the corresponding polyarene transition metal anions is underexplored, despite recognition of these highly reactive fragments as storable sources of atomic Mn−. Our application of this strategy provides structurally unique early‐late bimetallic species. These complexes incorporate bridging hydride ligands during their syntheses, the origin of which is elucidated via detailed isotopic labelling studies. Modification of ancillary ligand sterics and electronics alters the mechanism of bimetallic assembly; a trinuclear complex resulting from dinuclear C−H activation is demonstrated as an intermediate en route to formation of the bimetallic. Further validating the promise of this rational, bottom‐up approach, a unique tetranuclear species was synthesized, featuring a Ta centre bearing three Ta−Cu interactions.

Accessing Ta/Cu Architectures via Metal-Metal Salt Metatheses: Heterobimetallic C-H Bond Activation Affords μ-Hydrides.

We employ a metal-metal salt metathesis strategy to access low-valent tantalum-copper heterometallic architectures (Ta-μ2 -H2 -Cu and Ta-μ3 -H2 -Cu3 ) that emulate structural elements proposed for surface alloyed nanomaterials. Whereas cluster assembly with carbonylmetalates is well precedented, the use of the corresponding polyarene transition metal anions is underexplored, despite recognition of these highly reactive fragments as storable sources of atomic Mn- . Our application of this strategy provides structurally unique early-late bimetallic species. These complexes incorporate bridging hydride ligands during their syntheses, the origin of which is elucidated via detailed isotopic labelling studies. Modification of ancillary ligand sterics and electronics alters the mechanism of bimetallic assembly; a trinuclear complex resulting from dinuclear C-H activation is demonstrated as an intermediate en route to formation of the bimetallic. Further validating the promise of this rational, bottom-up approach, a unique tetranuclear species was synthesized, featuring a Ta centre bearing three Ta-Cu interactions.

Atomic regulation to improve the sensing-performance of CoPc and NiPc monolayer toward chloromethane molecule: Insights from DFT calculations

The development of a high-performance gas sensor for efficient detection of harmful chloromethane (CH3Cl) is of great importance to environmental monitoring and human health. Herein, the density functional theory (DFT) method was employed to compare the adsorption behaviors and electronic properties of CH3Cl on two-dimensional monometal modified phthalocyanines (CoPc, NiPc) and metal dimer modified phthalocyanines (CoTMPc and NiTMPc, TM = Ti∼Zn) surfaces. The studied results indicate that the CoPc and NiPc monolayers are not suitable as gas-sensitive materials for the detection of CH3Cl molecule due to their weak adsorption ability and low sensitivity. However, the adsorption strength and electronic properties of single-layer CoTMPc and NiTMPc towards CH3Cl can be effectively regulated through the synergistic effect of bimetallic species. Among them, the CoVPc, Co2Pc, NiVPc and NiZnPc monolayers exhibit moderate affinity for CH3Cl molecule, with the adsorption energies of −0.84 eV, −0.62 eV, −0.89 eV and −0.54 eV, respectively. The microscopic interaction mechanisms between CH3Cl molecule and bimetallic phthalocyanine monolayers are revealed through the analyses of total charge density, charge density difference and density of states. Furthermore, significant changes in bandgap are observed for Co2Pc and NiZnPc upon CH3Cl adsorption, while CoVPc and NiVPc monolayers exhibit noticeable variations in magnetic moments, indicating their high sensitivity towards CH3Cl. Considering the balance of adsorption strength, sensitivity and recovery time, the CoVPc, Co2Pc, NiVPc and NiZnPc monolayers are regarded as a great potential as gas-sensitive materials for recyclable CH3Cl gas sensors.

Acetoxy Group-Directed Regioselective C2 Alkenylation of Indoles via Pd-Ag Bimetallic Catalysis.

Regioselective C-H functionalizations of indoles reported to date with directing groups at C3 mainly rely on functional groups that are linked to the indole via C-C bonds. However, groups that are linked to the indole core by C-X linkages are also attractive due to the possibility of further modifications of the C-X bond. Herein, we report a 3-acetoxy directing group for the regioselective C2 alkenylation of indoles via a C-H activation-based, cross-dehydrogenative, oxidative Heck-type reaction. The reaction is catalyzed by Pd(II) and Ag(I) with stoichiometric Cu(II) as the oxidant and provides the 2-alkenylated indoles in yields of 52-84%. The reaction conditions are compatible with several functional groups at different positions as well as different N-protecting groups or free NH groups on the indole core. With respect to the alkene coupling partners, the reactions are successful with acrylates, vinyl sulfates, and phosphates. Specifically designed experiments, as well as density functional theory (DFT) computational studies, reveal that a heterodinuclear [Pd(μ-OAc)3Ag] bimetallic species is the actual catalyst responsible for the C-H alkenylation. A mechanistic path involving this catalytic species was also found to be favorable over other possible pathways for explaining the observed regioselectivity through DFT studies.

Synthesis of Vinyl Acetate Monomer Over PdCu Alloys: The Role of Surface Oxygenation in the Reaction Path

AbstractThis work uses sol–gel and sonochemical methods to prepare bimetallic PdCu catalysts supported on modified ZrO2 with Ti and Al. The catalysts are tested for vinyl acetate synthesis from ethylene, acetic acid, and oxygen, varying the reaction temperature for two catalysts prepared, which show higher activity. Catalysts characterization results show bimetallic species and distort alloys with a dispersed distribution of active metal onto the support. The in situ reaction by DRIFT‐MS identifies the surface formation of main intermediates like palladium acetate monomers and mono and bidentate intermediates, associated to vinyl acetate formation, like vinyl hydrogenated species over PdCu. Finally, this behavior will be attributed to the bimetallic distortions of PdCu samples, provided by interaction effects between PdCu and supports, indicating a more exposition of PdCu species suitable for the reaction, according to high‐resolution transmission microscopy electron microscopy results for PdCu/ZrTi sample. Thus, this sample exhibits a minimal formation of sub‐products and catalytic stability for 18 hh. These results evidence the participation of hydroxyls and oxygen vacancies of the catalyst in the catalytic reaction measured in situ, monitoring the products formed at the reactor outlet. Finally, it is proposed a reaction pathway as a function of reaction conditions.

Tuning the activity of cobalt 2-hydroxyphosphonoacetates-derived electrocatalysts for water splitting and oxygen reduction: Insights into the local order by pair distribution function analysis

Pyrophosphate- or phosphide-based iron/cobalt electrocatalysts were prepared from the metal (R,S)−2-hydroxyphosphonoacetates to evaluate the effects of metal composition, N-doping and P-enrichment on the electrocatalytic activity. Rietveld and Pair Distribution Function analysis were used to determine phase composition. Irrespectively of the amorphous or crystalline nature, all pyrolyzed solids transformed under OER operation into biphasic Fe/CoO(OH), composed of discrete clusters (size ≤ 20 Å). Carbon paper-supported Fe0.2Co0.8O(OH) electrocatalysts displayed the best OER performances (overpotentials of 270–279 mV at 10 mA·cm−2), attributable to the formation of highly active bimetallic intermediate species. For HER, increased concentration of o-CoP in phosphide-based electrocatalysts resulted in improved performance, up to an overpotential of 140 mV. Employed as anode in alkaline water splitting, amorphous Fe-doped cobalt pyrophosphate and phosphide-derived electrocatalysts showed a cell voltage of 1.58 V at 10 mA·cm−2, with comparable stability to that of RuO2 and requiring lower voltage demand at high current densities.

Size-Dependent Structures and Catalytic Properties of Supported Bimetallic PtSn Catalysts for Propane Dehydrogenation Reaction

Heterogeneous bimetallic catalysts are widely used in industrial processes, and the structural features of the bimetallic catalysts have profound impacts on their properties in numerous catalytic processes. Bimetallic nanoclusters with particle sizes ≤1 nm have shown better performances in various catalytic reactions in comparison to conventional bimetallic nanoparticles with sizes above 1 nm. Despite the progress made in recent years in the synthesis and catalytic studies of bimetallic nanoclusters, achieving a fundamental understanding of the structure–reactivity relationships at the molecular and atomic levels remains challenging because of the complexity of the bimetallic catalysts with particle sizes ≤1 nm. In this work, we have studied the structural features of supported bimetallic PtSn species with different sizes (∼0.6 to ∼1.6 nm), which is shown to be associated with the size-dependent formation process of bimetallic PtSn species according to theoretical modeling and experimental studies. Furthermore, the catalytic consequences of their size-dependent structural features are reflected in the dehydrogenation of propane to propylene, in which the subnanometer PtSn clusters are more active than the PtSn alloy nanoparticles.

Anti-Cancer and Radio-Sensitizing Properties of New Bimetallic (N-Heterocyclic Carbene)-Amine-Pt(II) Complexes.

Bioactive NHC-transition metal complexes have shown promise as anti-cancer agents, but their potential use as radiosensitizers has been neglected so far. We disclose here a new series of bimetallic platinum(II) complexes displaying NHC-type bridging ligands, (bis-NHC)[trans-Pt(RNH2)I2]2, that have been synthesized via a simple, two-step procedure. They display cytotoxicity in the micromolar range on cancerous cell lines, accumulate in cells, and bind to genomic DNA, by inducing DNA damages. Notably, these bimetallic complexes demonstrate significant radiosensitizing effects on both ovarian cells A2780 and nonsmall lung carcinoma cells H1299. Further investigations revealed that bimetallic species make irradiation-induced DNA damages more persistent by inhibiting repair mechanisms. Indeed, a higher and persistent accumulation of both γ-H2AX and 53BP1 foci post-irradiation was detected, in the presence of the NHC-Pt complexes. Overall, we provide the first in vitro evidence for the radiosensitizing properties of NHC-platinum complexes, which suggests their potential use in combined chemo-radio therapy protocols.

Umfassende Studie der Gesteigerten Reaktivität von Turbo‐Grignard‐Reagenzien**

AbstractSeit ihrer Einführung im Jahr 2004 revolutionierten Knochel's sogenannte Turbo‐Grignard‐Reagenzien die Anwendung der Grignard‐Reagenzien. Durch die einfache Zugabe von LiCl zu einem Magnesium‐Alkyl kann eine außerorderliche Steigerung der Reaktivität beobachtet werden. Die genaue Zusammensetzung der reaktiven Spezies blieb jedoch lange Zeit ein Rätsel, obwohl das reaktive Gemisch nicht nur in der Synthese breite Anwendung fand, sondern auch in anderen Bereichen wie der Materialwissenschaft Einzug hielt. Um dieses Rätsel zu lösen, kombinierten wir Einkristall‐Röntgendiffraktometrie mit NMR‐Spektroskopie in Lösung und vollendeten unsere Untersuchungen mit quantenchemischen Berechnungen. Durch die breite Vielfalt unserer Methoden, gelang uns ein Einblick in und eine erstmalige Erklärung für die außergewöhnliche Reaktivität dieses äußerst praktikablen Reagenzes, indem wir die Struktur der ersten bimetallischen Spezies [t‐Bu2Mg ⋅ LiCl ⋅ 4 THF] mit zwei tert‐Butylanionen am Magnesium‐zentrum und eingebautem Lithiumchlorid aufklärten.

Comprehensive Study of the Enhanced Reactivity of Turbo-Grignard Reagents.

Since its introduction in 2004, Knochel's so called Turbo-Grignard reagents revolutionized the usage of Grignard reagents. Through the simple addition of LiCl to a magnesium alkyl an outstanding increase in reactivity can be achieved. Though the exact composition of the reactive species remained mysterious, the reactive mixture itself is readily used not only in synthesis but also found its way into more distant fields like material science. To unravel this mystery, we combined single-crystal X-ray diffraction with in-solution NMR-spectroscopy and closed our investigations with quantum chemical calculations. Using such a variety of methods, we have gained insight into and an explanation for the extraordinary reactivity of this extremely convenient reagent by determining the structure of the first bimetallic reactive species [t-Bu2 Mg ⋅ LiCl ⋅ 4 thf] with two tert-butyl anions at the magnesium center and incorporated lithium chloride.

Exploration of Solid-State vs Solution-State Structure in Contact Ion Pair Systems: Synthesis, Characterization, and Solution-State Dynamics of Zinc Diphenyl Phosphate, [Zn{O2P(OPh)2}2], Donor-Base-Supported Complexes.

A family of zinc phosphate complexes supported by nitrogen donor-base ligands have been synthesized, and their molecular structures were identified in both the solid (X-ray crystallography) and solution state (DOSY NMR spectroscopy). [Zn{O2P(OPh)2}2]∞ (1), formed from the reaction of Zn[N(SiMe3)2]2 with HO(O)P(OPh)2 coordinates to donor-base ligands, i.e., pyridine (Py), 4-methylpyridine (4-MePy), 2,2-bipyridine (bipy), tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA), and 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3-TAC), to produce polymeric 1D structures, [(Py)2Zn{O2P(OPh)2}2]∞ (2) and [(4-MePy)2Zn{O2P(OPh)2}2]∞ (3), the bimetalic systems, [(Bipy)Zn{O2P(OPh)2}2]2 (4), [(TMEDA)Zn{O2P(OPh)2}2]2 (5), and [(Me3-TAC)Zn{O2P(OPh)2}2]2 (7), as well as a mono-nuclear zinc bis-diphenylphosphate complex, [(PMDETA)Zn{O2P(OPh)2}2] (6). 1H NMR DOSY has been used to calculate averaged molecular weights of the species. Studies are consistent with the disassembly of polymeric 3 into the bimetallic species [(Me-Py)2·Zn2{O2P(OPh)2}4], where the Me-Py ligand is in rapid exchange with free Me-Py in solution. Further 1H DOSY NMR studies of 4 and 5 reveal that dissolution of the complex results in a monomer dimer equilibrium, i.e., [(Bipy)Zn{O2P(OPh)2}2]2 ⇆ 2[(Bipy)Zn{O2P(OPh)2}2] and [(TMEDA)Zn{O2P(OPh)2}2]2 ⇆ 2[(TMEDA)Zn{O2P(OPh)2}2], respectively, in which the equilibria lie toward formation of the monomer. As part of our studies, variable temperature 1H DOSY experiments (223 to 313 K) were performed upon 5 in d8-tol, which allowed us to approximate the enthalpy [ΔH = -43.2 kJ mol-1 (±3.79)], entropy [ΔS = 109 J mol-1 K-1 (±13.9)], and approximate Gibbs free energy [ΔG = 75.6 kJ mol-1 (±5.62) at 293 K)] of monomer-dimer equilibria. While complex 6 is shown to maintain its monomeric solid-state structure, 1H DOSY experiments of 7 at 298 K reveal two separate normalized diffusion coefficients consistent with the presence of the bimetallic species [(TAC)2-xZn2{O2P(OPh)2}4], (x = 1 or 0) and free TAC ligand.

Cobalt-Promoted Noble-Metal Catalysts for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis.

Ammonia borane (AB) has been regarded as a promising material for chemical hydrogen storage. However, the development of efficient, cost-effective, and stable catalysts for H2 generation from AB hydrolysis remains a bottleneck for realizing its practical application. Herein, a step-by-step reduction strategy has been developed to synthesize a series of bimetallic species with small sizes and high dispersions onto various metal oxide supports. Superior to other non-noble metal species, the introduction of Co species can remarkably and universally promote the catalytic activity of various noble metals (e.g., Pt, Rh, Ru, and Pd) in AB hydrolysis reactions. The optimized Pt0.1%Co3%/TiO2 catalyst exhibits a superhigh H2 generation rate from AB hydrolysis, showing a turnover frequency (TOF) value of 2250 molH2 molPt-1 min-1 at 298 K. Such a TOF value is about 10 and 15 times higher than that of the monometal Pt/TiO2 and commercial Pt/C catalysts, respectively. The density functional theory (DFT) calculation reveals that the synergy between Pt and CoO species can remarkably promote the chemisorption and dissociation of water molecules, accelerating the H2 evolution from AB hydrolysis. Significantly, the representative Pt0.25%Co3%/TiO2 catalyst exhibits excellent stability, achieving a record-high turnover number of up to 215,236 at room temperature. The excellent catalytic performance, superior stability, and low cost of the designed catalysts create new prospects for their practical application in chemical hydrogen storage.

C-H activation in bimetallic rhodium complexes to afford N-heterocyclic carbene pincer complexes.

The pro-ligands 1,8-bis(di-R-phosphinomethyl)-2,3-dihydroperimidine (RH2Pm, R = phenyl, cyclohexyl) react with [RhCl(CE)(PPh3)2] (E = O, S) to afford the bimetallic complexes [RhCl(CE)(μ-RH2Pm)]2 (E = O, S). Upon heating, these species undergo double C-H activation to afford the N-heterocyclic carbene (NHC) pincer complexes [RhCl(RPm)]. Reduction of [RhCl(CO)(μ-PhH2Pm)]2 with KC8 results in the bimetallic rhodium(0) complex, [Rh(μ-CO)(PhH2Pm)]2, with a formal Rh-Rh bond and a hydrogen-bonding interaction between rhodium and the central methylene group (C-H⋯Rh = 2.802 Å). Upon treatment with tritylium, ferrocenium or triphenylcyclopropenium tetrafluoroborates this species undergoes double C-H activation to afford a mononuclear NHC pincer complex salt, [Rh(CO)(PhPm)]BF4. Treatment of [RhCl(CO)(PhH2Pm)]2 with lithium (trimethylsilyl)acetylide provides another bimetallic species, [Rh(CCSiMe3)(CO)(PhH2Pm)]2, however heating this species does not proceed cleanly to the monomeric NHC complex, [Rh(CCSiMe3)(CO)(PhPm)] which may however be obtained from [RhCl(RPm)] and LiCCSiMe3.

A family of edge-sharing bi-octahedral diruthenium(III,III) compounds containing Ru-Ru single bonds.

From paddlewheel starting reactants Ru2(R'CO2)4+, a family of edge-sharing bi-octahedral (ESBO) diruthenium(III,III) compounds has been prepared, formulated as Ru2(μ-O2CR')2(μ-OR)2(η-L)2 (1-10) [R' = CH3, R = CH3, L = acac (1), tfac (2); R' = CH3, R = CH2CH3, L = hfac (3); R' = CH2CH3, R = CH3, L = acac (4), tfac (5); R' = CH2CH3, R = CH2CH3, L = hfac (6); R' = CH2Cl, R = CH3, L = tfac (7); R' = CH2Cl, R = CH2CH3, L = hfac (8); R' = C6H5, R = CH3, L = tfac (9); and R' = H, R = CH3, L = acac (10); here, acac, tfac and hfac represent acetylacetone, trifluoroacetylacetone and hexafluoroacetylacetone, respectively]. Compounds 1-10 have a similar ESBO coordination geometry of the Ru(μ-O2CR')2(μ-OR)2Ru core with a Ru-Ru center chelated and bridged by two μ-O2CR' and two μ-OR in a trans manner, and each Ru center is also coordinated with a η2-L bidentate ligand. The Ru-Ru distances fall in the range of 2.4560(9)-2.4771(4) Å. The investigation of the electronic spectra and vibrational frequencies as well as theoretical studies with density functional theory (DFT) reveal that compounds 1-10 are ESBO bimetallic species of d5-d5 valence electron counts showing a σ2π2δ2δ*2π*2 electronic configuration. Varying -CH3 to -CF3 groups on the η2-L bidentate ligands coordinating to the Ru(μ-O2CR')2(μ-OR)2Ru core, and according to Raman spectrum measurements combined with theoretical calculations, the intense bands of compounds 1-10 appearing at ∼345 cm-1 in the small-wavenumber region can be assigned to the stretching of the Ru-Ru single bond.

Electrochemical Activation Applied to Perovskite Titanate Fibers to Yield Supported Alloy Nanoparticles for Electrocatalytic Application.

Active bi-metallic nanoparticles are of key importance in catalysis and renewable energy. Here, the in situ formation of bi-metallic nanoparticles is investigated by exsolution on 200nm diameter perovskite fibers. The B-site co-doped perovskite fibers display a high degree of exsolution, decorated with NiCo or Ni3 Fe bi-metallic nanoparticles with average diameter about 29 and 35nm, respectively. The perovskite fibers are utilized as cathode materials in pure CO2 electrolysis cells due to their redox stability in the CO/CO2 atmosphere. After in situ electrochemical switching, the nanoparticles exsolved from the perovskite fiber demonstrate an enhanced performance in pure CO2 electrolysis. At 900°C, the current density of solid oxide electrolysis cell (SOEC) with 200µm YSZ electrolyte supported NiFe doped perovskite fiber anode reaches 0.75Acm-2 at 1.6V superior to the NiCo doped perovskite fiber anode (about 1.5 times) in pure CO2 . According to DFT calculations (PBE-D3 level) the superior CO2 conversion on NiFe compared to NiCo bi-metallic species is related to an enhanced driving force for C-O cleavage under formation of CO chemisorbed on the nanoparticle and a reduced binding energy of CO required to release this product.

Bimetallic Ruthenium Nitrosyl Complexes with Enhanced Two-Photon Absorption Properties for Nitric Oxide Delivery.

One monometallic and three bimetallic ruthenium nitrosyl (RuNO) complexes are presented and fully characterized in reference to a parent monometallic complex of formula [FTRu(bpy)(NO)]3+ , where FT is a fluorenyl-substituted terpyridine ligand, and bpy the 2,2'-bipyridine. These new complexes are built with the new ligands FFT, TFT, TFFT, and TF-CC-TF (where an alkyne C≡C group is inserted between two fluorenes). The crystal structures of the bis-RuNO2 and bis-RuNO complexes built from the TFT ligand are presented. The evolution of the spectroscopic features (intensities and energies) along the series, at one-photon absorption (OPA) correlates well with the TD-DFT computations. A spectacular effect is observed at two-photon absorption (TPA) with a large enhancement of the molecular cross-section (σTPA ), in the bimetallic species. In the best case, σTPA is equal to 1523±98 GM at 700 nm, in the therapeutic window of transparency of biological tissues. All compounds are capable of releasing NO⋅ under irradiation, which leads to promising applications in TPA-based drug delivery.

Metal‐Mediated Interactions in Homo‐ and Heterobimetallic Edifices with Lanthanides: A Study in Solution

AbstractWe report here on the coordination properties of a series of lanthanide cations (Ln=La, Nd, Eu, Tb, Er) with a tripodal homoditopic ligand L, which is bearing three diamido‐dihydroxamate arms anchored on a tertiary amine. The complexes of L with lanthanides were studied in a MeOH/H2O (80/20 by weight) solvent and a marked size‐discriminating effect depending on the intramolecular interactions was observed in the tripodal dinuclear lanthanide edifice. Positive cooperative effects favour the formation of the bimetallic LLn2 complexes compared with the monometallic analogues for the heavier lanthanide cations (Eu, Tb, Er), while the lighter ones (La, Nd) show a decrease of cooperative interactions in the corresponding bimetallic species. Moreover, increased levels of heterobimetallic complexes are detected for Ln(III) pairs containing a lighter Ln(III) ion and a heavier one. In contrast with the adjunctive ligand exchange reported for LFe2 and CDTA, the corresponding substitution reaction for LLn2 occurs according to a disjunctive mechanism. Our work thus highlights the importance of the balance between the rigidity of a tripodal structure and the flexibility of the side arms to accommodate two trivalent cations in a supramolecular ensemble.

Supramolecular architectures in novel diphenyl(aryl)tin(IV) chlorides

The diphenyl(aryl)tin(IV) chloride [2-{(CH2O)2CH)}C6H4]SnPh2Cl (1) was prepared reacting [2-{(CH2O)2CH)}C6H4]Li with Ph2SnCl2. Hydrolysis of 1 with p-toluenesulfonic acid as a proton source gave [2-(OCH)C6H4]SnPh2Cl (2), which in turn was reacted with 2-(aminomethyl)pyridine, benzidine, 1-aminopyrene, in the absence of a solvent or catalyst, to afford the mono- or bimetallic species [2-(2′-PyCH2NCH)C6H4]SnPh2Cl (3), ClSnPh2[2-C6H4(4-CHN-1,1′-C6H4C6H4-4′-NCH)-2′-C6H4]Ph2SnCl (4) and [2-(C16H12NCH)C6H4]SnPh2Cl (5) (Py = pyridyl, C16H12 = pyrene). The compounds were characterized by multinuclear NMR spectroscopy and mass spectrometry in solution and IR spectroscopy in solid state. The molecular structures for compounds 1–5 were established by single-crystal X-ray diffraction. For all compounds the metal center is pentacoordinated with a distorted trigonal bipyramidal geometry and a (C,E)C2SnX core (E = O, Nimine) as a result of intramolecular E→Sn interactions. The presence of CH···Cl and CH···π (Phcentroid, Pycentroid, Pyrenecentroid) intermolecular interaction led to the formation of supramolecular associations in solid state for all compounds, thus, ribbon-like polymer occurs in crystal of 1, 2D layers arise in the case of 2 and 4, and complex 3D architectures are found in 3 and 5.