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Altres ajuts: acords transformatius de la UAB Altres ajuts: J.P. acknowledges financial support from the CB615921 project, the CB616406 project from "Fundació La Caixa". D.E. acknowledges the PIF predoctoral fellowship from the Universitat Autònoma de Barcelona. The behavior of coordination polymers (CPs) against external stimuli has witnessed remarkable attention, especially when the resulting CPs present reversible molecular arrays. Accordingly, CPs with these characteristics can lead to differences in their properties owing to these structural differences, being promising for their use as potential molecular switches with diverse applications. Herein, we have synthesized four Zn(II) CPs bearing α-acetamidocinnamic acid (HACA) and 4,4'-bipyridine (4,4'-bipy). The reaction between Zn(OAc)2·2H2O, HACA, and 4,4'-bipy yields {[Zn(ACA)2(4,4'-bipy)]·EtOH}n (1), which was used for the formation of three CPs through dissolution-recrystallization structural transformations (DRSTs): {[Zn(ACA)2(4,4'-bipy)]·2MeOH}n (2), {[Zn2(μ-ACA)2(ACA)2(4,4'-bipy)]·2H2O}n (3), and {[Zn3(μ-ACA)6(4,4'-bipy)]·0.75CHCl3}n (4). The study of the four crystal structures revealed that their secondary building units (SBUs) comprise monomeric, dimeric, and trimeric arrangements linked by 4,4'-bipy ligands. The fundamental role of the utilized solvent and/or temperature, as well as their effect on the orientation of the amide moieties driving the formation of the different SBUs is discussed. Furthermore, the reversibility and interconversion between the four CPs have been assayed. Finally, their solid-state photoluminescence has evinced that the effect of the amide moieties not only predetermine a different SBU but also lead to a different emission in 4 compared with 1-3.

A regular 2D array of crown molecules, which would spontaneously self-assemble into disordered molecular clusters, is obtained by exploiting a guest–host process, based on the chemical affinity between amino and carboxylic groups on a gold surface. First a carboxylic organic template is formed, which then serves as a host for amino-functionalized crown molecules. The amino-carboxylic interaction thereby drives the formation of a monolayer of guest molecules, regularly distributed at the nanometer scale, preventing their aggregation in unordered clusters observed on a bare gold surface. This method, which can be applied to other guest molecules, represents a novel route to overcome the shape-matching requirements of the standard guest–host architectures. Furthermore, it is intrinsically selective, due to the chemical nature of the anchoring process.

In this paper we consider the problem of characterizing the minimum energy configurations of a finite system of particles interacting between them due to attracting or repulsive forces given by a certain inter molecular potential. We limit ourselves to the cases of three particles arranged in a triangular array and that of four particles in a tetrahedral array. The minimization is constrained to fixed area in the case of the triangular array, and to fixed volume in the tetrahedral case. For a general class of inter molecular potentials we give conditions for the homogeneous configuration (either an equilateral triangle or a regular tetrahedron) of the array to be stable, that is, a minimizer of the potential energy of the system. To determine whether or not there exist other stable states, the system of first order necessary conditions for a minimum is treated as a bifurcation problem with the area or volume variable as the bifurcation parameter. Because of the symmetries present in our problem, we can apply the techniques of equivariant bifurcation theory to show that there exist branches of non--homogeneous solutions bifurcating from the trivial branch of homogeneous solutions at precisely the values of the parameter of area or volume for which the homogeneous configuration changes stability. For the triangular array, we construct numerically the bifurcation diagrams for both a Lennard--Jones and Buckingham potentials. The numerics show that there exist non--homogeneous stable states, multiple stable states for intervals of values of the area parameter, and secondary bifurcations as well., Keywords: molecular arrays, constrained optimization, equivariant bifurcation theory

Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 mu s and 2 nm, respectively., Scientific and Technological Research Council of Turkey (TÜBİTAK); IBM; Turkish National Academy of Sciences