RESUMEN

Nanorotor R1 (420 kHz) was assembled from five components utilizing three orthogonal interactions. Post-modification at the distal position generated the advanced six component rotor R2 (45 kHz). The decrease in R2 speed leads to the inhibition of a three-component reaction by reducing catalyst release.

RESUMEN

Photochemical valence bond isomerization of a crystalline Dewar benzene (DB) diacid monoanion salt with an acetophenone-linked piperazinium cation that serves as an intramolecular triplet energy sensitizer (DB-AcPh-Pz) exhibits a quantum chain reaction with as many as 450 product molecules per photon absorbed (Φ ≈ 450). By contrast, isomorphous crystals of the DB diacid monosalt of an ethylbenzene-linked piperazinium (DB-EtPh-Pz) lacking a triplet sensitizer showed a less impressive quantum yield of ca. Φ ≈ 22. To establish the critical importance of a triplet excited state carrier in the adiabatic photochemical reaction we prepared mixed crystals with DB-AcPh-Pz as a dilute triplet sensitizer guest in crystals of DB-EtPh-Pz. As expected from their high structural similarities, solid solutions were easily formed with the triplet sensitizer salt in the range of 0.1 to 10%. Experiments carried out under conditions where light is absorbed by the triplet sensitizer-linked DB-AcPh-Pz can be used to initiate a triplet state adiabatic reaction from 3DB-AcPh-Pz to 3HB*-AcPh-Pz, which can serve as a chain carrier and transfer energy to an unreacted DB-EtPh-Pz where exciton delocalization in the crystalline solid solution can help carry out an efficient energy transfer and enable a quantum chain employing the photoproduct as a triplet chain carrier. Excitation of mixed crystals with as little as 0.1% triplet sensitizer resulted in an extraordinarily high quantum yield Φ ≈ 517.

RESUMEN

When the slider-on-deck [Cu3(1)(2)]3+ and guest G were treated with palladium(II) ions, the biped 2 was released from [Cu3(1)(2)]3+ generating the nanocage [Pd2(2)4(G)]4+ with guest G being encapsulated (NetState-II). This transformation that was reversed by the addition of DMAP enabled modulation of both the overall fluorescence and the activity of copper(I) catalyzing an aza Hopf cyclization.

RESUMEN

To increase information density and security in communication, Nature at times encodes signals in the time domain, for instance, Ca2+ ion signals. Double encoding in the time domain operates beyond this level of security because the data are encoded in two time-dependent output signals showing distinct periods, frequencies, and full duration half-maxima. To illustrate such a protocol, a three-component ensemble consisting of a double ion-selective luminophore with two distinct receptor sites, hexacyclen, and diaza-18-crown-6 ether is demonstrated to act as a logic AND gate with Ag+ and Ca2+ ions as inputs. The gate shows an unprecedented 2-fold time-encoded fluorescence output at 590 and 488 nm based on metal ion pulses with distinct periods when trichloroacetic acid is applied as chemical fuel.

RESUMEN

Quantum chain reactions are characterized by the formation of several photoproducts per photon absorbed (ΦQC > 1) and constitute a promising signal amplification mechanism. The triplet-sensitized isomerization of Dewar benzene is known to undergo quantum chain reactions characterized by an adiabatic valence-bond isomerization to the excited state of Hückel benzene, which is able to transfer its triplet energy to a new ground state Dewar benzene that reacts to continue the chain. Given that diffusion-mediated energy transfer is the chain-limiting event in solution, we demonstrate here that reactions in crystals are significantly more efficient by taking advantage of energy transfer by a presumed exciton delocalization mechanism. Using Dewar benzenes with covalently attached, high energy triplet sensitizers we have demonstrated the efficiency of the solid state by the amplification of a quantum yield of ca. ΦQC ≈ 76 in acetonitrile solution to as much as ca. ΦQC ≈ 100-120 in submicron size specimens prepared by the re-precipitation method, and up to ca. ΦQC ≈ 300 with microcrystalline powders suspended in water.

RESUMEN

A multicomponent pseudorotaxane quadrilateral was reversibly toggled between three distinct switching states. Switching in the forward conversion was achieved by addition of H+ and K+ ions, and switching in the reverse direction was performed by addition of 18-crown-6 and 1-aza-18-crown-6. In both the forward and backward ways, the inputs operated an AND gate with distinct catalytic outputs. While in the forward direction the logic AND operation starting from a heteroleptic five-component assembly turned "ON" an imine hydrolysis as output (AND-1), in the inverse direction a Michael addition was ignited as the output starting from a seven-component aggregate following the AND gate logic (AND-2).

Asunto(s)

RESUMEN

Treatment of a crown-ether receptor and a silver(I)-loaded cyclam derivative (NetState-I) with a fuel acid reversibly afforded the protonated cyclam and the silver(I)-loaded crown ether (NetState-II). While NetState-I was catalytically OFF, a base-catalysed Michael addition and a silver(I)-catalysed oxime cyclisation reaction was pulsed under dissipative conditions in NetState-II.

RESUMEN

In State-I, a mixture comprising a DABCO-bridged tris(zinc-porphyrin) double decker and a free biped (=slider), catalysis was OFF. Acid addition (TFA or Di-Stefano fuel acid) to State-I liberated DABCO-H+ while generating a highly dynamic slider-on-deck device (State-II). The released DABCO-H+ acted as a base organocatalyst for a Knoevenagel reaction (catalysis ON). The system was reversed to State-I (catalysis OFF) by reducing the acidity in the system (by adding DBU or via the fuel-derived base).

RESUMEN

Reversible switching between the closed cyclic dimeric assembly [Cu2 (1)2 ]2+ (OFF state) and the extended dimeric homoleptic complex [FeCu2 (1)2 ]4+ (ON State) by addition/removal of Fe2+ triggered catalysis of a double-click reaction and high yield preparation of [2]rotaxanes. Mechanistic and computational studies provide valuable general insight for double-click strategies by revealing cooperative effects in the second cycloaddition step due to a distance-tolerant preorganization of the first-click product by the two copper(I)-loaded phenanthroline subunits of [FeCu2 (1)2 ]4+ .

RESUMEN

The three-component nanorotor [Cu2(S)(R)]2+ (k298 = 46.0 kHz) that is a catalyst for a CuAAC reaction binds the click product at each of its copper centers thereby creating a new platform and a dynamic slider-on-deck system. Due to this sliding motion (k298 = 65.0 kHz) the zinc-porphyrin bound N-methylpyrrolidine is efficiently released into solution and catalyzes a follow-up Michael addition.

RESUMEN

A 3-fold completive self-sorted library of dynamic motifs was integrated into the design of the pseudorotaxane-based rotor [Zn(2·H+)(3)(4)]2+ operating at k298 = 15.4 kHz. The rotational motion in the five-component device is based on association/dissociation of the pyridyl head of the pseudorotaxane rotator arm between two zinc(II) porphyrin stations. Addition of TFA or 2-cyano-2-phenylpropanoic acid as a chemical fuel to a zinc release system and the loose rotor components 2-4 enabled the liberated zinc(II) ions and protons to act in unison, setting up the rotor through the formation of a heteroleptic zinc complex and a pseudorotaxane linkage. With chemical fuel, the dissipative system was reproducibly pulsed three times without a problem. Due to the double role of the fuel acid, two kinetically distinct processes played a role in both the out-of-equilibrium assembly and disassembly of the rotor, highlighting the complex issues in multitasking of chemical fuels.

RESUMEN

Reactive (ReaxFF) molecular dynamic simulations were performed to elucidate the nature of interaction between hematite and carboxymethyl cellulose (CMC) considering effect of moisture and temperature. Simulations showed that the presence of moisture prohibited CMC to interact directly with hematite surface. However, the moisture helps to disperse CMC along the hematite surface thus maximizing the interaction. In dry condition, it was found that the negatively charged oxygen present in the functional groups and in CMC backbone (-CH2OCH2-) take part to form chemical bond with the positively charged surface Fe. The bonding interaction with polymer back bone is a new finding from this simulation. The binding energy estimated as -56.2 kcal/mol clearly indicates chemisorption with bond length ∼2.00 Å. Upon heating up the complex in presence of atmospheric oxygen it was observed that CMC decomposed at high temperature rather than desorbed from the surface. This study clearly shows that CMC is a suitable binder for iron ore pelletization and will pave the way for more rationale design of organic binders.

Asunto(s)

RESUMEN

Two dynamic slider-on-deck assemblies, i.e. a two-component threefold degenerate (k298 = 34.9 kHz) and a catenated three-component ninefold degenerate (k298 = 27.9 kHz) system, were quantitatively interconverted. Inspection of their computed structures revealed an allosteric effect on the sliding rates due to the spatial interaction between the components.

RESUMEN

A multi-device network mainly consisting of two two-component nanosliders was formed by self-sorting of six components. Addition/removal of zinc(ii) ions reversibly reorganized the network by chemical signaling involving the translocation of copper(i) from a relay station followed by the selective disassembly/assembly of one of both multi-component devices. The thus liberated machine parts served to erect a three-component nanoslider alongside the other unchanged two-component nanoslider.

RESUMEN

Remote control in an eight-component network commanded both the synthesis and shuttling of a [2]rotaxane via metal-ion translocation, the latter being easily monitored by distinct colorimetric and fluorimetric signals. Addition of zinc(II) ions to the red colored copper-ion relay station rapidly liberated copper(I) ions and afforded the corresponding zinc complex that was visualized by a bright sky blue fluorescence at 460 nm. In a mixture of all eight components of the network, the liberated copper(I) ions were translocated to a macrocycle that catalyzed formation of a rotaxane by a double-click reaction of acetylenic and diazide compounds. The shuttling frequency in the copper-loaded [2]rotaxane was determined to k 298=30 kHz (ΔH ≠=62.3±0.6 kJ mol-1, ΔS ≠=50.1±5.1 J mol-1 K-1, ΔG ≠ 298=47.4 kJ mol-1). Removal of zinc(II) ions from the mixture reversed the system back generating the metal-free rotaxane. Further alternate addition and removal of Zn2+ reversibly controlled the shuttling mode of the rotaxane in this eight-component network where the ion translocation status was monitored by the naked eye.

RESUMEN

The present paper adds the time domain to chemical ion translocation and (supra)molecular logic. When the self-sorted system of [Zn(1)]2+ + [Li(2)]+ + 3 (composed of hexacyclen 1, nanoswitch 2, luminophore 3) was treated with 2-cyano-2-phenylpropanoic acid (4) as a chemical fuel, protonation of 1 entailed a cascade translocation of first Zn2+, then Li+, resulting in the system [H(1)]+ + [Zn(2)]2+ + [Li(3)]+ that slowly reversed back to the initial state. The kinetic evolution of the lithium pulses was followed by changes in color and luminescence using the lithium-sensitive probe 3. The utility of fueling in combination with lithium pulses was exemplified among others by generating time-encoded SOS morse signals and implementing the time domain in two distinct AND gates.

RESUMEN

The quantitative double self-sorting between the three-component rectangle [Cu4(1)2(2)2]4+ and the four-component sandwich complex [Cu2(1)(2)(4)]2+ is triggered by inclusion and release of DABCO (4). The fully reversible and clean switching between two multicomponent supramolecular architectures can be monitored by fluorescence changes at the zinc porphyrin sites. The structural changes are accompanied by a huge spatial contraction/expansion of the zinc porphyrin-zinc porphyrin distances that change from 31.2/38.8 Å to 6.6 Å and back. The supramolecular interconversion was used for the highly selective detection of DABCO in a mixture of other similar compounds.

RESUMEN

Framework 1, a freely rotating turnstile, is transformed by sequential metal ion addition into the coordination-based double-minimum rotors [M2(1)]2n+ that operate at 8 kHz (M = Zn2+; n = 2) and 30 kHz (M = Cu+; n = 1). In a network with the fluorescent receptor 2, the metal ion exchange at [M2(1)]2n+ and thus indirectly the rotor speed is reported by distinct fluorescence changes at 2.

RESUMEN

The silver(I) catch-release system composed of nanoswitch 1 and the anthracene-appended crown ether 2 is infallibly driven by chemical triggers and ion transfer. Any state of the silver(I) translocation is self-reported by a ratiometric emission signature at 472 and 554 nm. In the self-sorted networked state I, the silver(I) ions are tightly shielded inside nanoswitch [Ag(1)]+ ("catch") so that their catalytic activity is zero while emission at 554 nm is maximum. Addition of zinc(II) releases silver(I) from [Ag(1)]+ and generates the catalytically active and fluorescent complex [Ag(2)]+. In this networked state II ("release") both catalytic activity and emission at 472 nm are maximum. Removal of the original trigger regenerates networked state I. ON/OFF control and recycling of catalyst was demonstrated over three in situ cycles.

Asunto(s)

RESUMEN

Three-component nanorotor R1 ( k298 = 80 kHz) and two-component slider-on-deck DS2 ( k298 = 440 kHz) were prepared from rotator S1 and stator [Cu3(1)]3+ and from S2 and deck D, respectively. Mixing of R1 with DS2 leads to clean metathesis, furnishing the slower nanodevices R2 ( k298 = 29.6 kHz) and DS1 ( k298 = 32.2 kHz). Exchange of the piston rods S1 and S2 is completed within 22 min (uncatalyzed) or 3 min (catalyzed) at 298 K.