scholarly journals Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling

2019 ◽  
Author(s):  
Vladyslav Savchenko ◽  
Markus Koch ◽  
Aleksander S. Pavlov ◽  
Marina Saphiannikova ◽  
Olga Guskova
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Computer Modelling ◽  
Uv Light ◽  
Light Exposure ◽  
Light Stimulus ◽  
Intermolecular Forces ◽  
Binding Energies ◽  
Simulation Techniques ◽  
Assembly Mechanism

In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analysed theoretically applying a combination of computer simulation techniques. Without a light stimulus, the trans-stars build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies -- fibers, spheres, gels and others. Upon UV light exposure, the azobenzene arms isomerise from thermodynamically stable planar trans- to a metastable kinked cis-state influencing the aggregate morphology. Here, we determine the most favourable mutual orientations of the \textit{trans}-stars in the stack in terms of (i) the pi-pi distance between the cores lengthwise the aggregate, (ii) the star slipped displacements and (iii) the rotation promoting the helical twist and chirality of the aggregate by calculating the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks made of trans-azobenzene stars in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of such stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moment and the binding energies as the functions of the columnar length using molecular dynamics trajectories, and conclude about the cooperative nature of this process.

scholarly journals Stacks of Azobenzene Stars: Self-Assembly Scenario and Stabilising Forces Quantified in Computer Modelling

Molecules ◽  
2019 ◽  
Vol 24 (23) ◽  
pp. 4387 ◽  
Author(s):  
Vladyslav Savchenko ◽  
Markus Koch ◽  
Aleksander S. Pavlov ◽  
Marina Saphiannikova ◽  
Olga Guskova
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Computer Modelling ◽  
Light Stimulus ◽  
Dipole Moments ◽  
Intermolecular Forces ◽  
Binding Energies ◽  
The Self ◽  
Assembly Mechanism ◽  
Lateral Displacements

In this paper, the columnar supramolecular aggregates of photosensitive star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core and azobenzene arms are analyzed theoretically by applying a combination of computer simulation techniques. Without a light stimulus, the azobenzene arms adopt the trans-state and build one-dimensional columns of stacked molecules during the first stage of the noncovalent association. These columnar aggregates represent the structural elements of more complex experimentally observed morphologies—fibers, spheres, gels, and others. Here, we determine the most favorable mutual orientations of the trans-stars in the stack in terms of (i) the π – π distance between the cores lengthwise the aggregate, (ii) the lateral displacements due to slippage and (iii) the rotation promoting the helical twist and chirality of the aggregate. To this end, we calculate the binding energy diagrams using density functional theory. The model predictions are further compared with available experimental data. The intermolecular forces responsible for the stability of the stacks in crystals are quantified using Hirshfeld surface analysis. Finally, to characterize the self-assembly mechanism of the stars in solution, we calculate the hydrogen bond lengths, the normalized dipole moments and the binding energies as functions of the columnar length. For this, molecular dynamics trajectories are analyzed. Finally, we conclude about the cooperative nature of the self-assembly of star-shaped azobenzenes with benzene-1,3,5-tricarboxamide core in aqueous solution.

THEORY–EXPERIMENT RELATIONSHIP OF THE "SHRINKING HOT GIANT" ROAD OF DYNAMIC FULLERENE SELF-ASSEMBLY IN HOT CARBON VAPOR

NANO ◽  
2007 ◽  
Vol 02 (01) ◽  
pp. 21-30 ◽  
Author(s):  
S. IRLE ◽  
G. ZHENG ◽  
Z. WANG ◽  
K. MOROKUMA
Keyword(s):  
Formation Mechanism ◽  
Self Assembly ◽  
Density Functional ◽  
Dissipative Structures ◽  
Model Systems ◽  
Irreversible Processes ◽  
Fullerene Cage ◽  
Carbon Vapor ◽  
Assembly Mechanism ◽  
Cage Size

Though subject to intensive studies, the formation mechanism of buckminsterfullerene C 60 and related higher fullerenes has long evaded discovery. To elucidate their atomistic self-assembly mechanism, we have performed high-temperature quantum chemical molecular dynamics simulations on carbon vapor model systems initially consisting of C 2 molecules. Our simulations reveal a coherent mechanism how highly ordered fullerene cages naturally self-assemble under nonequilibrium conditions, following a series of irreversible processes from the polymerization of C 2 molecules to vibrationally excited giant fullerenes, which then shrink by C 2 evaporation down to the smallest spherical, isolated pentagon rule obeying species C 70 and C 60 as the smallest and kinetically most stable species of the shrinking process. We show that the potential energy surface associated with giant fullerene cage growth, measured by an average cluster curvature, is downhill all the way, and in agreement with high-level energetics from density functional theory. This fullerene formation mechanism is a good example of dynamic self-assembly leading to dissipative structures far from thermodynamic equilibrium, and the "shrinking hot giant" road provides a natural explanation for the observed cage size distributions in a random optimization process consistent with several important experimental observations.

Mechanism of Surfactant Removal from Ordered Nanocomposite Silica Thin Films by Deep-UV Light Exposure

2003 ◽  
Vol 788 ◽  
Author(s):  
Andrew M. Dattelbaum ◽  
Meri L. Amweg ◽  
Julia D. Ruiz ◽  
Laurel E. Ecke ◽  
Andrew P. Shreve ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Self Assembly ◽  
Uv Light ◽  
Light Exposure ◽  
Complete Removal ◽  
Combined Application ◽  
Silica Thin Films ◽  
Deep Uv ◽  
Surfactant Removal

ABSTRACTIn recent years, methods have been developed for the generation of complex ordered nanocomposite materials through organic templating of inorganic structures. One approach involves preparation of composite materials by an evaporation induced self-assembly process involving organization of organic surfactants and formation of inorganic silica from soluble precursors. Recently, we have shown that deep-UV light (185–254nm) is efficient at removing the surfactant microphase for a routine production of well-ordered mesoporous silica thin films. Here we probe the evolution of surfactant removal from nanocomposite thin film silica mesophases as a function of deep-UV exposure using a combined application of FTIR and single wavelength ellipsometry. Taken together, these data indicate that surfactant removal occurs in a step-wise fashion with the formation of oxidized intermediates prior to complete removal of the surfactant from the thin film.

Stronger Intermolecular Forces or Closer Molecular Spacing? Key Impact Factor Research of Gelator Self-Assembly Mechanism

Langmuir ◽  
2017 ◽  
Vol 33 (50) ◽  
pp. 14389-14395 ◽  
Author(s):  
Si Chen ◽  
Zhihang An ◽  
Xiaoqian Tong ◽  
Yining Chen ◽  
Meng Ma ◽  
...  
Keyword(s):  
Impact Factor ◽  
Self Assembly ◽  
Intermolecular Forces ◽  
Assembly Mechanism

The self-assembly mechanism of the Lindqvist anion [W6O19]2− in aqueous solution: a density functional theory study

2012 ◽  
Vol 41 (37) ◽  
pp. 11361 ◽  
Author(s):  
Zhong-Ling Lang ◽  
Wei Guan ◽  
Li-Kai Yan ◽  
Shi-Zheng Wen ◽  
Zhong-Min Su ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Density Functional Theory ◽  
Self Assembly ◽  
Density Functional ◽  
The Self ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Assembly Mechanism

scholarly journals Synthesis, Self-Assembly and Photoresponsive Behavior of Liquid Crystals Based on Azobenzene

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1560
Author(s):  
Yaming Wu ◽  
Yuhai Liu ◽  
Jianxiang Chen ◽  
Runmiao Yang
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Self Assembly ◽  
Driving Force ◽  
1H Nmr Spectroscopy ◽  
Uv Light ◽  
Light Exposure ◽  
Scanning Calorimetry ◽  
Stimulus Response ◽  
Cis Isomer

A new amphiphilic surfactant (C4-Azo-C5-HDA) was formed by liquid crystals (LCs) based on azobenzene, whose structures were characterized by 1H-NMR spectroscopy. The reversible hydrogelation upon changes in temperature and light exposure was also studied. Under the irradiation of UV light, the trans-isomer of C4-Azo-C5-HDA rapidly photoisomerized to the cis-isomer, resulting in rapid disruption of the gel. The thermotropic liquid crystal behavior of the gelator was investigated via Differential Scanning Calorimetry (DSC) and Polarizing Optical Microscopy (POM). The biocompatibility experiment of multi-stimulus response of the liquid crystal provides a potential driving force for the development of biomaterials.

scholarly journals Structural and Nanotribological Properties of a BODIPY Self-Assembly

2021 ◽  
Vol 9 ◽  
Author(s):  
Shanchao Tan ◽  
Wendi Luo ◽  
Yongjie Zhang ◽  
Xiang-Kui Ren ◽  
Yuhong Liu ◽  
...  
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Supramolecular Assembly ◽  
Dft Method ◽  
The Self ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Assembly Mechanism

Boron-dipyrromethenes (BODIPY) are promising functional dyes, whose exceptional optical properties are closely related to their supramolecular assembly. Herein, the self-assembly of a BODIPY derivative functionalized with uracil groups is explicitly and thoroughly investigated by using scanning tunneling microscopy (STM). Based on the simulation and calculation by density functional theory (DFT) method, it can be concluded that the construction of ordered self-assembly structure is attributed to the formation of hydrogen bonds between uracil groups. Moreover, the nanotribological property of the self-assembly on HOPG surface is measured by using atomic force microscopy (AFM). The effort on self-assembly of the BODIPY derivative could enhance the understanding of surface assembly mechanism.

scholarly journals MOLECULAR SWITCH BASED ON BITHIOPHENE-AZOBENZENE: HOW TO CONTROL CONDUCTANCE THROUGH THE MONOLAYER USING LIGHT

2021 ◽  
pp. 7-20
Author(s):  
Владислав Анатольевич Савченко ◽  
Ольга Александровна Гуськова
Keyword(s):  
Density Functional ◽  
Rational Design ◽  
Molecular Design ◽  
Uv Light ◽  
Light Stimulus ◽  
Gold Cluster ◽  
Stimuli Responsive ◽  
Anchor Group ◽  
Light Stimuli ◽  
Conductance Ratio

Молекулярные переключатели на основе азобензола (азо) являются светочувствительными молекулами, которые могут переключаться между двумя конфигурационными состояниями под действием света. Светочувствительные азо -монослои можно использовать для модуляции работы выхода, то есть они влияют на свойства электродов. В данной работе мы отвечаем на вопрос, что происходит со структурами, электронными свойствами и перераспределением заряда в монослоях азобитиофена (азо-бт) в зависимости от светового стимула, используя теорию функционала плотности. Моделируются два типа переключателей, различающихся расположением азо и бт от группы пришивки молекулы к поверхности: азо-бт и бт-азо . Один из них (бт-азо) описан в литературе, другой же является продуктом молекулярного дизайна. Мы описываем транс- и цис-изомеры для каждого переключателя, находящегося в контакте с кластером золота. Наше моделирование объясняет гигантское соотношение в проводимости ON/OFF-состояний при воздействии УФ-излучения на монослой улучшенной электронной связью между цис-изомерами (состояние ON) и кластером золота. Транс-изомеры же (OFF состояние) моделируемых переключателей играют роль изоляторов. Кроме того, мы показываем, какие именно свойства улучшаются после молекулярного дизайна. Данное исследование открывает новые возможности в разработке инновационных модификаций поверхности электродов. Molecular switches based on azobenzene (azo) are defined as light-responsive molecules which can change between two configurational states under light stimuli. Responsive azo monolayers can be used to modulate the work function, i.e. they tune the properties of the interfaces at the electrodes. In this work, we investigate what happens to the structures, electronic properties, and the charge redistribution within azo-bithiophene (azo-bt) monolayers depending on the light stimulus using density functional theory. Two types of switches differing in the order of azo and bt counting from the anchor group are modelled: azo-bt and bt-azo . One of them (bt-azo) is known from the literature, the remaining one is a product of rational design. We describe trans- and cis-isomers for each switch being in a contact with a gold cluster. Our simulations explain a giant ON/OFF conductance ratio upon UV light stimulus by improved electronic coupling between the cis-isomers (ON-state) and the gold cluster. The trans-isomers (OFF-state) of the simulated switches play the role of the insulators. Moreover, we show which molecular properties are enchanced by molecular design. This study opens up new avenues to the development of the innovative design of electrode surface modifications.

scholarly journals Theoretical and X-ray studies on the cyclisation of 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1Hpyrazole- 4-carbonitriles and 2-amino-3-(3-aryltriaz-1-en-1-yl)maleonitriles: A comparison study

2021 ◽  
Author(s):  
Amal Al-Azmi ◽  
◽  
Firas F. Awwadi ◽  
Keyword(s):  
Self Assembly ◽  
Density Functional ◽  
Phenyl Group ◽  
Intermolecular Forces ◽  
Crystalline Lattice ◽  
Comparison Study ◽  
Density Functional Theory Study ◽  
Structural Isomers ◽  
Functional Theory ◽  
X Ray

The present work investigates attempts to cyclise 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1H-pyrazole- 4-carbonitriles to the desired pyrazolo[3,4-d][1,2,3]triazinimine derivatives. The cyclisations were unfruitful, and a density functional theory study was performed. This revealed the 1-phenyl-5-(3-aryltriaz-1-en-1-yl)-1H-pyrazole-4-carbonitriles are more stable than the targeted pyrazolo[3,4-d][1,2,3]triazinimine derivatives, indicating that their cyclisation is thermodynamically disfavoured; the reactant 8c is more stable than the predicted six-membered ring products 9c by 5 kJ/mol. The effect of isomerisation of the methoxy-phenyl group in the self-assembly of 8c and 8d in the crystalline lattice was investigated. The intermolecular forces in solid state were analysed in the two structural isomers 8c and 8d using calculated HirshFeld surface; the analysis indicates that the intermolecular forces are stronger in 8c than 8d and hence 8c is denser than 8d by 0.071g/mL.

scholarly journals Self-Assembled Nanoscaled Metalloporphyrin for Optical Detection of Dimethylmethylphosphonate

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Mingbo Wu ◽  
Hongsheng Yang ◽  
He Wei ◽  
Xueli Hu ◽  
Bo Qu ◽  
...  
Keyword(s):  
Self Assembly ◽  
Metal Ion ◽  
Density Functional ◽  
Detection Limits ◽  
Functional Materials ◽  
Binding Energies ◽  
Central Metal ◽  
Mixed Solution ◽  
Functional Theory ◽  
Axial Ligands

The self-assembly approach has been widely adopted in the effort to design and prepare functional materials. Herein, we report the synthesis and optical properties of metalloporphyrin nanoparticles. Nanoscaled particles of 5,10,15,20-tetraphenylporphyrin manganese (MnTPP) and 5,10,15,20-tetraphenylporphyrin indium (InTPP) were produced in the water/dimethylsulfoxide (DMSO) mixed solution by self-assembly approach. The absorbance intensity at the characteristic peak of the monomeric and nanoscaled metalloporphyrins decreased when they interact with dimethylmethylphosphonate (DMMP). Detection limits of MnTPP and InTPP nanoparticles to DMMP were 10−9 and 10−10 L/L, respectively, and detection limits of monomeric MnTPP and InTPP to DMMP were 10−6 and 10−7 L/L, respectively. Density functional theory (DFT) calculations on MnTPP and InTPP with DMMP as axial ligands had been performed in the B3LYP/6-31g (d) approximation. Their optimized geometries and binding energies were found to depend very strongly on the central metal ion, and InTPP was more sensitive for DMMP detection in contract to MnTPP. All the experimental and theoretical results demonstrated that nanoscaled metalloporphyrin have potential prospects in determination for public safety.

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