177 research outputs found
Molecular Tuning in Diaryl-Capped Pyrrolo [2,3-d:5,4-dâ˛] bisthiazoles: Effects of Terminal Aryl Unit and Comparison to Dithieno[3,2-b:2â˛,3â˛-d]pyrrole Analogues
A series of six conjugated oligomers consisting of a central pyrrolo[2,3-d:5,4-dâ˛]bisthiazole (PBTz) end-capped with either thienyl, furyl, or phenyl groups have been prepared from N-alkyl-and N-aryl-pyrrolo[2,3-d:5,4-dâ˛]bisthiazoles via Stille and Negishi cross-coupling. The full oligomeric series was thoroughly investigated via photophysical and electrochemical studies, in parallel with density functional theory (DFT) calculations, in order to correlate the cumulative effects of both aryl end-groups and N-functionalization on the resulting optical and electronic properties. Through comparison with the analogous dithieno[3,2-b:2â˛,3â˛-d]pyrrole (DTP) materials, the effect of replacing DTP with PBTz on the material HOMO energy and visible light absorption is quantified.This research was funded by MICINN (project PID2019-110305GB-I00) and by Junta de AndalucĂa (P09FQM-4708 and P18-FR-4559). Partial funding for open access charge: Universidad de MĂĄlag
Totally asymmetric exclusion process with long-range hopping
Generalization of the one-dimensional totally asymmetric exclusion process
(TASEP) with open boundary conditions in which particles are allowed to jump
sites ahead with the probability is studied by
Monte Carlo simulations and the domain-wall approach. For the
standard TASEP phase diagram is recovered, but the density profiles near the
transition lines display new features when . At the first-order
transition line, the domain-wall is localized and phase separation is observed.
In the maximum-current phase the profile has an algebraic decay with a
-dependent exponent. Within the regime, where the
transitions are found to be absent, analytical results in the continuum
mean-field approximation are derived in the limit .Comment: 10 pages, 9 figure
Critical behaviour of the 1D q-state Potts model with long-range interactions
The critical behaviour of the one-dimensional q-state Potts model with
long-range interactions decaying with distance r as has been
studied in the wide range of parameters and . A transfer matrix has been constructed for a truncated range of
interactions for integer and continuous q, and finite range scaling has been
applied. Results for the phase diagram and the correlation length critical
exponent are presented.Comment: 20 pages plus 4 figures, Late
A Comparison of Two Zinc Hydride Catalysts for Terminal Alkyne CâH Borylation/Hydroboration and the Formation of 1,1,1-Triborylalkanes by Tandem Catalysis Using ZnâH and BâH Compounds
Invaded cluster algorithm for a tricritical point in a diluted Potts model
The invaded cluster approach is extended to 2D Potts model with annealed
vacancies by using the random-cluster representation. Geometrical arguments are
used to propose the algorithm which converges to the tricritical point in the
two-dimensional parameter space spanned by temperature and the chemical
potential of vacancies. The tricritical point is identified as a simultaneous
onset of the percolation of a Fortuin-Kasteleyn cluster and of a percolation of
"geometrical disorder cluster". The location of the tricritical point and the
concentration of vacancies for q = 1, 2, 3 are found to be in good agreement
with the best known results. Scaling properties of the percolating scaling
cluster and related critical exponents are also presented.Comment: 8 pages, 5 figure
Low coordinate NHC-Zinc-Hydride Complexes Catalyze Alkyne C-H Borylation and Hydroboration using Pinacolborane
Organozinc
compounds containing sp, sp<sup>2</sup>, and sp<sup>3</sup> CâZn
moieties undergo transmetalation with pinacolborane
(HBPin) to produce ZnâH species and organoboronate esters (RBPin).
This ZnâC/HâB metathesis step is key to enabling zinc-catalyzed
borylation reactions, and it is used in this work to develop both
terminal alkyne CâH borylation and internal alkyne hydroboration.
These two conversions can be combined in one pot to achieve the zinc-catalyzed
conversion of terminal alkynes to 1,1-diborylated alkenes without
isolation of the sensitive (to protodeboronation) alkynyl boronate
ester intermediates. Mechanistic studies involving the isolation of
intermediates, stoichiometric experiments, and DFT calculations all
support mechanisms involving organozinc species that undergo metathesis
with HBPin. Furthermore, zinc-catalyzed hydroboration can proceed
via a hydrozincation step, which does not require any exogenous catalyst
in contrast to all previously reported alkyne hydrozincations. Bulky <i>N</i>-heterocyclic carbenes (NHCs) are key for effective catalysis
as the NHC steric bulk enhances the stability of the NHCâZn
species present during catalysis and provides access to low-coordinate
(NHC)ÂZnâH cations that are electrophilic yet Brønsted
basic. This work provides an alternative approach to access synthetically
desirable pinacolâorganoboronate esters using earth-abundant
metal-based borylation catalysts
On the thermodynamics of first-order phase transition smeared by frozen disorder
The simplified model of first-order transition in a media with frozen
long-range transition-temperature disorder is considered. It exhibits the
smearing of the transition due to appearance of the intermediate inhomogeneous
phase with thermodynamics described by the ground state of the short-range
random-field Ising model. Thus the model correctly reproduce the persistence of
first-order transition only in dimensions d > 2, which is found in more
realistic models. It also allows to estimate the behavior of thermodynamic
parameters near the boundaries of the inhomogeneous phase.Comment: 4 page
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