Hydrogen-Bonded Rosettes of Aminotriazines for Selective-Ion Recognition

Ion recognition is still an emerging topic in supramolecular chemistry and has aroused great attention in the last few years. In this work, we have examined the assemblies of selected hexameric rosettes of melamine and ammeline and their capacities to host halide and alkali ions in the gas phase and in water. Using relativistic dispersion-corrected density functional theory (DFT-D), we first studied the stability and the effect of introducing monovalent anions (Cl-, Br-, and I-) and cations (Na+, K+, and Rb+) in the center of the rosette´s cavity. Finally, we explored the interactions in two stacked rosettes with an interlayer ion. Our computations reveal that amine-substituted triazines are promising candidates for anion and cation recognition either in self-assembled monolayers or pillar array structures. The anion recognition process is governed by both the electrostatic and charge-transfer (donor-acceptor) interactions, while the cation recognition is governed by electrostatic and polarization. In addition, melamine and ammeline could constitute a potent mixture for dual-ion recognition strategies.Fil: Petelski, Andre Nicolai. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Vrije Universiteit Amsterdam; Países Bajos. Universidad Tecnológica Nacional. Facultad Regional Resistencia. Departamento de Ingeniería Química. Laboratorio de Química Teórica y Experimental; ArgentinaFil: Fonseca Guerra, Célia. Vrije Universiteit Amsterdam; Países Bajo

NMR 1 H-Shielding Constants of Hydrogen-Bond Donor Reflect Manifestation of the Pauli Principle

NMRspectroscopy is one of the most useful methods for detection andcharacterization of hydrogen bond (H-bond) interactions in biological systems.For H-bonds X-H⋯Y, where X and Y are O or N, it is generally believed that adecrease of 1H-shielding constants relates to a shortening of H-bondsdonor-acceptor distance. Here, we investigated computationally the trend of1H-shielding constants for hydrogen-bonded protons in a series of GuanineC8-substituted GC pair model compounds as a function of the molecularstructure. Furthermore, the electron density distribution around the hydrogenatom was analyzed with the Voronoi deformation density (VDD) method. Ourfindings demonstrate that 1H-shielding values of the hydrogen bond aredetermined by the depletion of charge around the hydrogen atom which stems fromthe fact that electrons obey the Pauli exclusion principle.Fil: Zarycz, Maria Natalia Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Fonseca Guerra, Célia. Vrije Unviversiteit; Países Bajos. Leiden University; Países Bajo

Differential stabilization of adenine quartets by anions and cations

We have investigated the structures and stabilities of four different adenine quartets with alkali and halide ions in the gas phase and in water, using dispersion-corrected density functional theory at the BLYP-D/TZ2P level. First, we examine the empty quartets and how they interact with alkali cations and halide anions with formation of adenine quartet–ion complexes. Second, we examine the interaction in a stack, in which a planar adenine quartet interacts with a cation or anion in the periphery as well as in the center of the quartet. Interestingly, for the latter situation, we find that both cations and anions can stabilize a planar adenine quartet in a stack

A especialização inteligente na área central da cidade do Porto: domínios, ação pública e desafios

A Comissão Europeia tem vindo a promover as estratégias de especialização inteligente como forma de cada país e, sobretudo, de cada região identificar áreas de investimento prioritárias, potenciando os seus principais ativos e tornando-os em vantagens competitivas face a outros territórios. A geografia da especialização inteligente regional reflete matizes resultantes da sua implementação à escala local. A estratégia de especialização inteligente da Região Norte de Portugal encontra-se patente nas abordagens de política pública do Município do Porto. Tendo como objeto de análise a área central da cidade do Porto, esta comunicação visa identificar e caracterizar os domínios de especialização inteligente mais evidenciados, bem como perceber as dinâmicas recentes e o papel da ação pública. Para o efeito, recorreu-se a uma abordagem predominantemente qualitativa, com recurso à análise de conteúdo de documentos estratégicos e à realização de entrevistas semi-diretivas a agentes locais dos diversos setores culturais, criativos e lúdicos

Understanding chemical reactivity using the activation strain model

Contains fulltext : 216198.pdf (publisher's version ) (Closed access

Nature of Alkali- and Coinage-Metal Bonds Versus Hydrogen Bonds

We have quantum chemically studied the structure and nature of alkali- and coinage-metal bonds (M-bonds) versus that of hydrogen bonds between A-M and B- in archetypal [A-M center dot center dot center dot B](-) model systems (A, B=F, Cl and M=H, Li, Na, Cu, Ag, Au), using relativistic density functional theory at ZORA-BP86-D3/TZ2P. We find that coinage-metal bonds are stronger than alkali-metal bonds which are stronger than the corresponding hydrogen bonds. Our main purpose is to understand how and why the structure, stability and nature of such bonds are affected if the monovalent central atom H of hydrogen bonds is replaced by an isoelectronic alkali- or coinage-metal atom. To this end, we have analyzed the bonds between A-M and B- using the activation strain model, quantitative Kohn-Sham molecular orbital (MO) theory, energy decomposition analysis (EDA), and Voronoi deformation density (VDD) analysis of the charge distribution.O.L. gratefully acknowledges the UPV/EHU for her postdoctoral grant. This work was supported by funding provided by the Spanish Ministry of Economy and Competitiveness (MINECO CTQ2013-45415P and CTQ2016-80375P), the Gobierno Vasco-Eusko Jaurlaritza (Grant IT673-13) and the Netherlands Organization for Scientific Research (NWO). We also thank SURFsara for the support in using the Lisa Computer Cluster, and DIPC and SGI-IZO-SGIker (UPV/EHU) for generous allocation of computational resource

Impact of Conformational Effects on the Ring–Chain Equilibrium of Hydrogen-Bonded Dinucleosides

This is the peer reviewed version of the following article: Chemistry - A European Journal 24.46 (2018): 11983-11991, which has been published in final form at https://doi.org/10.1002/chem.201801704 . This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsSupramolecular ring-versus-chain equilibria are ubiquitous in biological and synthetic systems. Understanding the factors that decide whether a system will fall on one side or the other is crucial to the control of molecular self-assembly. This work reports results with two kinds of dinucleoside monomers, in which the balance between closed cycles and open polymers is found to depend on subtle factors that rule conformational equilibria, such as steric hindrance, intramolecular interactions, or π-conjugation pathwaysFunding from the European Research Council (ERC-StG 279548) and MINECO (CTQ2014-27729-P and CTQ2017-84727-P) is gratefully acknowledged (DGR). CFG gratefully acknowledges financial support from the Netherlands Organization for Scientific Research NWO (ECHO

Aggregation induced emission of a new naphthyridine-ethynyl-gold(I) complex as a potential tool for sensing guanosine nucleotides in aqueous media

A new organometallic alkynyl-gold(I) complex, capable of exhibiting Aggregation Induced Emission was designed and synthesized. The linear complex structure possesses a central Au(I) atom, bearing two axial ligands: (1) 1,3,5-Triaza-7-phosphaadamantane; and (2) 2- acetamido-7-ethynyl-1,8-naphthyridine. While the former accounts for its partial solubility in aqueous environment, the latter acts as a receptor unit for binding guanosine nucleotides and derivatives via multiple hydrogen bonding. At high concentrations, aggregation of the complex was observed by the formation of new absorption (λmax ~ 400 nm) and emission bands (550-700 nm). Formation of aggregates of ca. 60 nm diameter was confirmed with Small Angle X-Ray Scattering (SAXS). Disruption of the aggregates in the presence of guanosine derivatives resulted in a ratiometric signal with apparent association constants in the order of 105 M-1 and high sensitivity (around 63% signal change) which are, to the best of our knowledge, in line with the highest recorded for nucleotide sensing based on hydrogen bonding that are capable of working in water. Computational studies indicate the presence of additional hydrogen bonding interactions that account for the strong binding of the Au(I) complex to phosphorylated Guanosine nucleotides

Computational understanding and experimental characterization of twice-as-smart quadruplex ligands as chemical sensors of bacterial nucleotide second messengers

A twice-as-smart ligand is a small molecule that experiences a structural switch upon interaction with its target (i.e., smart ligand) that concomitantly triggers its fluorescence(i.e., smart probe). Prototypes of twice-as-smart ligands were recently developed to track and label G-quadruplexes: these higher-order nucleic acid structures originate in the assembly of four guanine(G)-rich DNA or RNA strands, whose stability is imparted by the formation and the self-assembly of G-quartets. The firstprototypes of twice-as-smart quadruplex ligands were designed to exploit the self-association of quartets, being themselves synthetic G-quartets. While their quadruplex recognition capability has been thoroughly documented, some doubts remain about the precise photophysical mechanism that underlies their peculiar spectroscopic properties. Here, we uncovered this mechanism via complete theoretical calculations. Collected information was then used to develop of a novel application of twice-as-smart ligands, as efficnt chemical sensors of bacterial signaling pathways via the fluorescentdetection of naturally occurring extracellular quadruplexes formed by cyclic dimeric guanosine monophosphate (c-di-GMP)