We have synthesized a novel class of dendrimers, consisting of a polysulfurated pyrene core with appended poly(thiophenylene) dendrons (PyG0, PyG1, and PyG2, see Scheme 1), which exhibit remarkable ...photophysical and redox properties. In dichloromethane or cyclohexane solution they show a strong, dendron‐localized absorption band with a maximum at around 260 nm and a band in the visible region with a maximum at 435 nm, which can be assigned to the pyrene core strongly perturbed by the four sulfur substituents. The dendrimers exhibit a strong (Φ=0.6), short‐lived (τ=2.5 ns) core‐localized fluorescence band with maximum at approximately 460 nm in cyclohexane solution at 293 K. A strong fluorescence is also observed in dichloromethane solution at 293 K, in dichloromethane/chloroform rigid matrix at 77 K, and in the solid state (powder) at room temperature. The dendrimers undergo reversible chemical and electrochemical one‐electron oxidation with formation of a strongly colored deep blue radical cation. A second, reversible one‐electron oxidation is observed at more positive potential values. The photophysical and redox properties of the three dendrimers are finely tuned by the length of their branches. The strong blue fluorescence and the yellow to deep blue color change upon reversible one‐electron oxidation can be exploited for optoelectronic devices.
Optoelectronic devices: Dendrimers containing a pyrene core and polysulfurated branches show intense blue luminescence and a reversible color change from light yellow to deep blue upon mono‐oxidation by chemical (AuCl4−) or electrochemical methods (see picture). These properties could be exploited for optoelectronic devices.
Suitably designed molecular and supramolecular species are capable of combining light and chemical inputs to perform functions that mimic those of macroscopic devices. This paper describes the ...working principles of molecular‐level photochemionic devices for i) chemical switching of photonic input/output signals, ii) chemical tuning of photonic input/output signals, and iii) the transformation of chemical and/or optical signals for logic operation.
Photochemionic devices are molecular or supramolecular systems wherein information transfer and processing is accomplished by using light, molecules, and ions as input/output signals (see figure). They operate in solution and take inspiration from information processing in living organisms. Advances in this field could lead to the design and construction of a “molecular computer”.
We have investigated the interaction of Co2+ ions (as nitrate salt) with dendrimers of the poly(propylene amine) family functionalized in the periphery with fluorescent dansyl units. Each dendrimer n ...D, where the generation number n goes from 1 to 5, comprises 2( n +1) dansyl functions in the periphery and 2( n +1) − 2 tertiary amine units in the interior. For comparison purposes, the behavior of a monodansyl reference compound (I) has also been investigated. The results obtained have shown that: (i) the absorption and fluorescence spectra of the reference compound I are not affected by addition of Co2+ ions; (ii) in the case of the dendrimers, the absorption spectra are unaffected, but a strong quenching of the fluorescence of the peripheral dansyl units is observed; (iii) the fluorescence quenching takes place by a static mechanism involving coordination of metal ions in the interior of the dendrimers; (iv) metal ion coordination by the dendrimers is a fully reversible process; (v) a strong amplification of the fluorescence quenching signal is observed with increasing dendrimer generation. For the larger dendrimers (n = 3, 4, and 5), at very low metal ion concentration 1:1 metal/dendrimer species are formed, in which the Co2+ ion guest quenches each one of the dansyl units that becomes excited after light absorption.
A unique methodology to measure gas fluxes of SO2 and NO2 from ships using optical remote sensing is described and demonstrated in a feasibility study. The measurement system is based on Differential ...Optical Absorption Spectroscopy using reflected skylight from the water surface as light source. A grating spectrometer records spectra around 311 nm and 440 nm, respectively, with the telescope pointed downward at a 30° angle from the horizon. The mass column values of SO2 and NO2 are retrieved from each spectrum and integrated across the plume. A simple geometric approximation is used to calculate the optical path. To obtain the total emission in kg h−1 the resulting total mass across the plume is multiplied with the apparent wind, i.e. a dilution factor corresponding to the vector between the wind and the ship speed. The system was tested in two feasibility studies in the Baltic Sea and Kattegat, from a CASA-212 airplane in 2008 and in the North Sea outside Rotterdam from a Dauphin helicopter in an EU campaign in 2009. In the Baltic Sea the average SO2 emission out of 22 ships was (54 ± 13) kg h−1, and the average NO2 emission was (33 ± 8) kg h−1, out of 13 ships. In the North Sea the average SO2 emission out of 21 ships was (42 ± 11) kg h−1, NO2 was not measured here. The detection limit of the system made it possible to detect SO2 in the ship plumes in 60% of the measurements when the described method was used. A comparison exercise was carried out by conducting airborne optical measurements on a passenger ferry in parallel with onboard measurements. The comparison shows agreement of (−30 ± 14)% and (−41 ± 11)%, respectively, for two days, with equal measurement precision of about 20%. This gives an idea of the measurement uncertainty caused by errors in the simple geometric approximation for the optical light path neglecting scattering of the light in ocean waves and direct and multiple scattering in the exhaust plume under various conditions. A tentative error budget indicates uncertainties within 30–45% but for a reliable error analysis the optical light path needs to be modelled. A ship emission model, FMI-STEAM, has been compared to the optical measurements showing an 18% overestimation and a correlation coefficient (R2) of 0.6. It is shown that a combination of the optical method with modelled power consumption can estimate the sulphur fuel content within 40%, which would be sufficient to detect the difference between ships running at 1% and at 0.1%, limits applicable within the IMO regulated areas.
The assembly of a discrete number of molecular components to yield supramolecular species can provide a higher level of organization of the receiving "matter" of a photon. The design of structurally ...organized and functionally integrated systems capable of elaborating the energy and information input of photons to perform complex functions is discussed.
Three different multicomponent molecular systems have been synthesized by means of the three-dimensional template effect of copper(I). These systems incorporate both a coordinating ring ...(2,9-diphenyl-1,10-phenanthroline-containing 30-membered ring) and a molecular string which consists of two different coordination sites (2,9-disubstituted-1,10-phenanthroline and 5,5‘ ‘-disubstituted-2,2‘:6‘,2‘ ‘-terpyridine unit). Each end of the string could be functionnalyzed by a small group or by a bulky stopper (tris(p-tert-butylphenyl)(4-hydroxyphenyl)methane), leading to an unstoppered compound, to a semi-rotaxane, or to a real rotaxane. As in the case of a disymmetrical copper 2-catenane, large reversible molecular motions have been induced both electrochemically and photochemically. The driving force of the rearrangement processes is the high stability of two markedly different coordination environments for the copper(I) and copper(II) ions. In the copper(I) state, two phenanthroline units (one of the ring, one of the string) interact with the metal ion in a tetrahedral geometry (CuI (4)), whereas in the copper(II) state, one phenanthroline belonging to the ring and the terpyridine of the string afford a five-coordinate geometry (CuII (5)). The rates of the molecular motion processes (from CuII (4) to CuII (5) and from CuI (5) to CuI (4)) are respectively faster and slower (minutes time scale) as compared to those for the catenane species. This result could be interpreted on the basis of structural differences between the rotaxane and catenane systems.
Adalimumab (Ada) treatment is an available option for pediatric Crohn's disease (CD) and the published experience as rescue therapy is limited.
We investigated Ada efficacy in a retrospective, ...pediatric CD cohort who had failed previous infliximab treatment, with a minimum follow-up of 6 months.
In this multicenter study, data on demographics, clinical activity, growth, laboratory values (CRP) and adverse events were collected from CD patients during follow-up. Clinical remission (CR) and response were defined with Pediatric CD Activity Index (PCDAI) score ≤10 and a decrease in PCDAI score of ≥12.5 from baseline, respectively.
A total of 44 patients were consecutively recruited (mean age 14.8 years): 34 of 44 (77%) had active disease (mean PCDAI score 24.5) at the time of Ada administration, with a mean disease duration of 3.4 (range 0.3-11.2) years. At 6, 12, and 18 months, out of the total of the enrolled population, CR rates were 55%, 78%, and 52%, respectively, with a significant decrease in PCDAI scores (
<0.01) and mean CRP values (mean CRP 5.7 and 2.4 mL/dL, respectively;
<0.01) at the end of follow-up. Steroid-free remission rates, considered as the total number of patients in CR who were not using steroids at the end of this study, were 93%, 95%, and 96% in 44 patients at 6, 12, and 18 months, respectively. No significant differences in growth parameters were detected. In univariate analysis of variables related to Ada efficacy, we found that only a disease duration >2 years was negatively correlated with final PCDAI score (
<0.01). Two serious adverse events were recorded: 1 meningitis and 1 medulloblastoma.
Our data confirm Ada efficacy in pediatric patients as second-line biological therapy after infliximab failure. Longer-term prospective data are warranted to define general effectiveness and safety in pediatric CD patients.
A mechanical switch in a 2catenane, made up of a cyclobis(paraquat‐p‐phenylene) tetracation interlocked with a macrocyclic polyether containing a redox‐active tetrathiafulvalene (TTF) unit and a ...1,5‐dioxynaphthalene ring system, can be thrown either chemically or electrochemically. The neutral TTF unit resides “inside” the tetracationic cyclophane in the reduced state and “alongside” it in the oxidized species (TTF+/ TTF2+). Switching between the reduced (I4+) and oxidized state (I5+(I6+)) is accompanied by a dramatic color change.
We describe the photochemical behavior of aqueous solutions containing the Co(CN)6 3- complex ion and the trans-chalcone form Ct of the 4‘-methoxyflavylium ion (AH+). It is shown that, under the ...experimental conditions used, the photochemical reaction leading from Ct to AH+ shows an off − on − off behavior upon excitation with a continuous light source or with successive light flashes. The described systems perform as threshold devices and as XOR (eXclusive OR) logic gates. They behave as rudimental artificial neuron-like systems in the sense that their outputs (formation of the AH+ species, with a consequent change in the spectroscopic properties) are the result of an elaboration of two distinct (light) inputs by chemical reactions in solution.
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