Formation Of Molecular Clusters Research Articles

Direct formation of single crystalline molecular clusters with disulfide bonding from thiol-containing triptycene derivatives

Abstract When a DMF solution of 1,8,13-trimercaptotriptycene is allowed to stand under an inert atmosphere, a single crystalline molecular cluster with disulfide bonding results. Likewise, several thiol-containing triptycene derivatives yield single crystalline disulfide-containing clusters with different structural patterns. One of these clusters featuring a densely arranged tetrapod-like disulfide moiety exhibits a particularly high refractive index of 1.75, much higher than that of the others, although the sulfur contents of these clusters are comparable.

Manipulation of aurophilicity in constructed clusters of gold(I) complexes with boosted luminescence and smart responsiveness

High-performance luminescent gold(I) complexes have attracted considerable attention due to their potential applications in various fields, but their construction is a significantly challenging task. Herein, we designed and synthesized a series of novel dinuclear gold(I) complexes 1–4 based on 1,2-bis(diphenylphosphino)benzene and 1,4-bis(diphenylphosphino)benzene frameworks, where para-substitutions of benzene ring were employed for comparison and bulky t-butyl groups were introduced into carbazole ligands to assist flexibly regulating the aurophilicity. Among them, the structure of complex 1 was confirmed by single-crystal X-ray diffraction, and all the complexes exhibited typical aggregation-induced emission characteristics. Due to the construction of intramolecular aurophilicity and the formation of molecular clusters, noticeable enhancement of the luminescent efficiency was achieved for the core complex 1. Together with the introduction of flexible t-butyl groups, good responsiveness towards external mechanical force and solvent vapors were also realized. Moreover, the specific bioimaging ability of complex 1 towards cancer cells was demonstrated. Thus, this work presents the crucial capability of aurophilic manipulation in tuning the luminescence and smart behaviors of gold complexes, and it will open a new route to developing high-performance luminescent materials.

Effect of lanthanide doping on the optical properties of Barium Yttrium Borate

Barium Yttrium Borate Ba3Y(BO3)3 was prepared using high-temperature solid state reaction at 800°C. X-ray diffraction technique was used to confirm the crystal structure of the prepared host material Ba3Y(BO3)3. It was doped with Europium and Terbium. The doping concentration was changed as 1%, 2%, 5% and 7% mol.% in the Barium Yttrium Borate sample. FESEM analysis showed the formation of hexagonal molecular clusters of some nanometre range. The photoluminescence behaviour of all samples was studied in detail. Optimum PL intensity was recorded for 2 mol.% of Eu3+ doped in Ba3Y(BO3)3. CIE coordinates obtained for 7 mol.% doped in Ba3Y(BO3)3 showed better chromaticity near standard values as per the European Broadcasting Union (EBU). Using testing tools, such as SEM, the morphology of the prepared sample was examined. The red emission colour is due to transitions 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 , resulting in emitted wavelengths of 594 and 612 nm in Ba3Y(BO3)3:Eu3+ , respectively. The emission wavelengths of 543 nm and 551 nm are due to a transition 5 D 4 → 7 F 5 taking place in Ba3Y(BO3)3:Tb3+. This luminescent material could also be used as a downconverter material for different types of solar cells.

Clusterome: A Comprehensive Data Set of Atmospheric Molecular Clusters for Machine Learning Applications.

Formation and growth of atmospheric molecular clusters into aerosol particles impact the global climate and contribute to the high uncertainty in modern climate models. Cluster formation is usually studied using quantum chemical methods, which quickly becomes computationally expensive when system sizes grow. In this work, we present a large database of ∼250k atmospheric relevant cluster structures, which can be applied for developing machine learning (ML) models. The database is used to train the ML model kernel ridge regression (KRR) with the FCHL19 representation. We test the ability of the model to extrapolate from smaller clusters to larger clusters, between different molecules, between equilibrium structures and out-of-equilibrium structures, and the transferability onto systems with new interactions. We show that KRR models can extrapolate to larger sizes and transfer acid and base interactions with mean absolute errors below 1 kcal/mol. We suggest introducing an iterative ML step in configurational sampling processes, which can reduce the computational expense. Such an approach would allow us to study significantly more cluster systems at higher accuracy than previously possible and thereby allow us to cover a much larger part of relevant atmospheric compounds.

Atmospheric Sulfuric Acid-Multi-Base New Particle Formation Revealed through Quantum Chemistry Enhanced by Machine Learning.

The formation of molecular clusters and secondary aerosols in the atmosphere has a significant impact on the climate. Studies typically focus on the new particle formation (NPF) of sulfuric acid (SA) with a single base molecule (e.g., dimethylamine or ammonia). In this work, we examine the combinations and synergy of several bases. Specifically, we used computational quantum chemistry to perform configurational sampling (CS) of (SA)0-4(base)0-4 clusters with five different types of bases: ammonia (AM), methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), and ethylenediamine (EDA). Overall, we studied 316 different clusters. We used a traditional multilevel funnelling sampling approach augmented by a machine-learning (ML) step. The ML made the CS of these clusters possible by significantly enhancing the speed and quality of the search for the lowest free energy configurations. Subsequently, the cluster thermodynamics properties were evaluated at the DLPNO-CCSD(T0)/aug-cc-pVTZ//ωB97X-D/6-31++G(d,p) level of theory. The calculated binding free energies were used to evaluate the cluster stabilities for population dynamics simulations. The resultant SA-driven NPF rates and synergies of the studied bases are presented to show that DMA and EDA act as nucleators (although EDA becomes weak in large clusters), TMA acts as a catalyzer, and AM/MA is often overshadowed by strong bases.

Weak intra and intermolecular interactions via aliphatic hydrogen bonding in piperidinium based ionic Liquids: Experimental, topological and molecular dynamics studies

Hydrogen bonding interaction plays an important role in the stability of the building blocks of various materials. In present work, both intra- and inter- molecular aliphatic H-bond interactions stabilize piperidinium based ionic liquids (ILs: MPDNP, PPDNP, BPDNP and HPDNP) and play crucial role on physical properties of these ILs. Further, the significance of multiple intermolecular aliphatic H-bonding interactions in the formation of molecular clusters, ion-pair, dimeric ion-pairs, and also corrugated sheet array of ILs has been investigated here. UV–vis study of these ILs has also been performed to understand the electronic properties of these ILs in solution. The DSC, TGA, SCXRD, vibrational spectroscopic techniques have been employed to understand the effect of intra and intermolecular aliphatic hydrogen bonding interaction on physical property and molecular cluster formation of ILs in their ambient phases. The DSC and TGA studies demonstrate that the intermolecular interaction between cation and anion remains nearly unvaried on increasing of alkyl chain length but the physical properties of ILs changes. SCXRD and vibrational spectroscopic techniques describe the presence of aliphatic H-bonding interaction between ion pairs, dimeric ion-pairs and corrugated sheet having contacts in the range 2.46–2.63 Å. NBO analysis is performed to calculate the second order stabilization energy for better understanding of the intramolecular interactions at a molecular level. The second order stabilization energy for the transfer lone pair charge of oxygen to antibonding orbital of CH is measured in the range of 3.46–3.73 Kcal/mol for ILs. Topological and ab initio molecular dynamics (AIMD) simulations studies are performed to get closer insight of underlying interactions and the stability of ILs. AIMD study depicts that the total energy of IL attains a maximum of −1045.84 a.u. close to 100 fs, whereas relatively low energy is measured between 250 and 350 fs.

In situ observation of the on-surface thermal dehydrogenation of n-octane on Pt(111).

The catalytic dehydrogenation of alkanes constitutes a key step for the industrial conversion of these inert sp3-bonded carbon chains into other valuable unsaturated chemicals. To this end, platinum-based materials are among the most widely used catalysts. In this work, we characterize the thermal dehydrogenation of n-octane (n-C8H18) on Pt(111) under ultra-high vacuum using synchrotron-radiation X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning tunneling microscopy, combined with ab initio calculations. At low activation temperatures, two different dehydrogenation stages are observed. At 330 K, n-C8H18 effectively undergoes a 100% regioselective single C-H bond cleavage at one methyl end. At 600 K, the chemisorbed molecules undergo a double dehydrogenation, yielding double bonds in their carbon skeletons. Diffusion of the dehydrogenated species leads to the formation of carbon molecular clusters, which represents the first step towards poisoning of the catalyst. Our results reveal the chemical mechanisms behind the first stages of alkane dehydrogenation on a platinum model surface at the atomic scale, paving the way for designing more efficient dehydrogenation catalysts.

Формирование молекулярных кластеров серебра полимерно-солевым методом в пористых стеклах

A methodology for the formation of molecular clusters of silver in silicate nanoporous glasses has been developed. Composite materials containing molecular clusters of silver, silver nanoparticles and zinc oxide have been synthesized. The synthesis was carried out by impregnation of porous glasses in aqueous solutions of silver and zinc nitrates stabilized with high-molecular polyvinylpyrrolidone, followed by heat treatment of samples for decomposition of metal nitrates and polymer. Spectral-luminescent properties of composites have been investigated.

Formation of molecular clusters of silver by polymer-salt method in porous glasses

A methodology for the formation of molecular clusters of silver in silicate nanoporous glasses has been developed. Composite materials containing molecular clusters of silver, silver nanoparticles and zinc oxide have been synthesized. The synthesis was carried out by impregnation of porous glasses in aqueous solutions of silver and zinc nitrates stabilized with high-molecular polyvinylpyrrolidone, followed by heat treatment of samples for decomposition of metal nitrates and polymer. Spectral-luminescent properties of composites have been investigated. Keywords: porous glass, zinc oxide, silver molecular clusters, silver nanoparticles, spectral-luminescent properties.

Origin of the near 400 nm Absorption and Emission Band in the Synthesis of Cesium Lead Bromide Nanostructures: Metal Halide Molecular Clusters Rather Than Perovskite Magic-Sized Clusters

In the synthesis of cesium lead bromide (CsPbBr3) perovskite quantum dots, with an electronic absorption and emission band around 510 nm, and perovskite magic-sized clusters (PMSCs), with an electronic absorption and emission band around 430 nm, another distinct absorption and emission around 400 nm is often observed. While many would attribute this band to small perovskite particles, here we show strong evidence that this band is a result of the formation of lead bromide molecular clusters (PbBr2 MCs) passivated with ligands, which do not contain the A component of the ABX3 perovskite structure. This evidence comes from a systematic comparative study of the reaction products with and without the A component under otherwise identical experimental conditions. The results support that the near 400 nm band originates from ligand-passivated PbBr2 MCs. This observation seems to be quite general and is significant in understanding the nature of the reaction products in the synthesis of metal halide perovskite nanostructures.

Massive Assessment of the Binding Energies of Atmospheric Molecular Clusters.

Quantum chemical studies of the formation and growth of atmospheric molecular clusters are important for understanding aerosol particle formation. However, the search for the lowest free-energy cluster configuration is extremely time consuming. This makes high-level benchmark data sets extremely valuable in the quest for the global minimum as it allows the identification of cost-efficient computational methodologies, as well as the development of high-level machine learning (ML) models. Herein, we present a highly versatile quantum chemical data set comprising a total of 11 749 (acid)1-2(base)1-2 cluster configurations, containing up to 44 atoms. Utilizing the LUMI supercomputer, we calculated highly accurate PNO-CCSD(F12*)(T)/cc-pVDZ-F12 binding energies of the full set of cluster configurations leading to an unprecedented data set both in regard to sheer size and with respect to the level of theory. We employ the constructed benchmark set to assess the performance of various semiempirical and density functional theory methods. In particular, we find that the r2-SCAN-3c method shows excellent performance across the data set related to both accuracy and CPU time, making it a promising method to employ during cluster configurational sampling. Furthermore, applying the data sets, we construct ML models based on Δ-learning and provide recommendations for future application of ML in cluster configurational sampling.

Synergistic Enhancement of Lead and Selenate Uptake at the Barite (001)-Water Interface.

The interactions of heavy metals with minerals influence the mobility and bioavailability of toxic elements in natural aqueous environments. The sorption of heavy metals on covalently bonded minerals is generally well described by surface complexation models (SCMs). However, understanding sorption on sparingly soluble minerals is challenging because of the dynamically evolving chemistry of sorbent surfaces. The interpretation can be even more complicated when multiple metal ions compete for sorption. In the present study, we observed synergistically enhanced uptake of lead and selenate on the barite (001) surface through two sorption mechanisms: lattice incorporation that dominates at lower coverages and two-dimensional monolayer growth that dominates at higher coverages. We also observed a systematic increase in the sorption affinity with increasing co-sorbed ion coverages, different from the assumption of invariant binding constants for individual adsorption processes in classical SCMs. Computational simulations showed thermodynamically favorable co-incorporation of lead and selenate by simultaneously substituting for barium and sulfate in neighboring sites, resulting in the formation of molecular clusters that locally match the net dimension of the substrate lattice. These results emphasize the importance of ion-ion interactions at mineral-water interfaces that control the fate and transport of contaminants in the environment.

Contribution of Methanesulfonic Acid to the Formation of Molecular Clusters in the Marine Atmosphere.

Because of the lack of long-term measurements, new particle formation (NPF) in the marine atmosphere remains puzzling. Using quantum chemical methods, this study elucidates the cluster formation and further growth of sulfuric acid-methanesulfonic acid-dimethylamine (SA-MSA-DMA) clusters, relevant to NPF in the marine atmosphere. The cluster structures and thermochemical parameters of (SA)n(MSA)m(DMA)l (n + m ≤ 4 and l ≤ 4) systems are calculated using density functional theory at the ωB97X-D/6-31++G(d,p) level of theory, and the single-point energies are calculated using high-level DLPNO-CCSD(T0)/aug-cc-pVTZ calculations. The calculated thermochemistry is used as input to the Atmospheric Cluster Dynamics Code (ACDC) to gain insight into the cluster dynamics. At ambient conditions (298.15 K, 1 atm), we find that the distribution of outgrowing clusters primarily consists of SA and DMA, with a minor contribution from the mixed SA-MSA-DMA clusters. At lower temperature (278.15 K, 1 atm) the distribution broadens, and clusters containing one or more MSA molecules emerge. These findings show that in the cold marine atmosphere MSA likely participates in atmospheric NPF.

Molecular clusters played an important role in the adsorption of polycyclic aromatic hydrocarbons (PAHs) on carbonaceous materials

Polycyclic aromatic hydrocarbons (PAHs) are one of the most frequently detected hydrophobic organic contaminants (HOCs) in the environment. They may form clusters because of the strong hydrophobic and π-π electron-donor-acceptor (EDA) interactions among PAHs molecules. However, previous experimental studies and theoretical simulations generally ignored the impact of molecular clusters on the adsorption, which may result in the misunderstanding of the environmental fate and risk. In this work, naphthalene (NAP), phenanthrene (PHE), and pyrene (PYR) were selected to investigate intermolecular interaction as well as the consequent impact on their adsorption on graphene. The density field of C atoms in equilibrium configurations of self-interacted PAHs suggested that the formation of PAHs molecular clusters was a spontaneous process, and was favored in solvents with stronger polarity and for PAHs with more benzene rings. It should be noted that the molecular dynamics simulations with the initial state of molecular clusters matched better with the published experimental results compared with those of individual PAHs. The formed compact PAHs clusters in polar solvents increased the apparent PAHs adsorption, because of their higher hydrophobic and π-π EDA interactions. This study emphasized that the self-interaction of PAHs should be carefully considered in both experimental and theoretical simulation studies.

The Influence of the Structural Features of Molecules on Spontaneous Polarization Value in Induced Ferroelectric Liquid Crystal Systems

The occurrence of the large value of spontaneous polarization is established in LC system whose composition`s molecular structure does not satisfy the obligatory conditions for the occurrence of spontaneous polarization that are imposed by theory on a molecular structure. The essential role of short range intermolecular forces in the process of ferroelectric phase transition in the studied LC systems is shown. It was found that for {CC}, {DD} and {AD} interactions the most beneficial molecules` packing in terms of energy is the antiparallel one . In the case of {AA} and {AC} interactions both parallel and are equally beneficial in terms of energy. The possibility of formation of molecular clusters–dimers is shown. It is concluded that these are stabilized, in particular, by dipole–dipole interaction of molecules. A dimer model for increasing the value of spontaneous polarization is proposed.

Qualitative and quantitative study of intermolecular weak interactions for aminosalicylic acid isomers by terahertz spectroscopy

AbstractIn the field of chemical science, the development of new drugs, the formation of crystals and molecular clusters, and the optimization of drug safety and efficacy are all closely related to weak molecular interactions. In this paper, the salicylic drugs 4‐aminosalicylic acid (4‐ASA) and 5‐aminosalicylic acid (5‐ASA) are used as the research objects. First, the terahertz (THz) absorption spectra of the two isomers were measured in the range of .4–2.0 THz by terahertz time‐domain spectroscopy (THz‐TDS). Then the unit cells were calculated by using density functional theory (DFT). We found that the characteristic absorption peaks of the experimental spectra were basically consistent with the theoretical calculation. In addition, under the solvent model, the free energy of dissolution and the free energy of the systems were considered and calculated, and the results showed that solvation had a certain influence on the position and intensity of spectral absorption peaks. In order to further explore the origin of the characteristic absorption peaks, the vibrational properties of the unit cell model were analyzed using the potential energy distribution (PED) method. At the same time, the weak interactions of the system were qualitatively and quantitatively analyzed by interaction region indicator (IRI) and energy decomposition analysis based on forcefield (EDA‐FF) methods, respectively. The results show that the absorption peaks of 4‐ASA and 5‐ASA are mainly derived from the vibration mode of dihedral angle torsion. The weak interactions in the 4‐ASA are dominated by dispersion, while they are dominated by electrostatic and dispersion in the 5‐ASA. Therefore, it is an effective way to identify isomers and study intermolecular weak interactions by using THz‐TDS combined with PED, IRI, and EDA‐FF.

Study of diacetyl-water clusters using Raman scattering and theoretical calculations

In this work, the intermolecular interactions of diacetyl and water molecules were studied using the vibration spectrum. The Raman scattering spectra obtained in the range of 500– 2000 cm−1 were analyzed and compared with the results of calculations. For the first time аlso, the charge density distribution and 3D potential energy graphs are examined using simulations for diacetyl molecules. With the increase in the number of molecules at the formation of molecular clusters with the water molecule, the saturation of the intermolecular interaction energy corresponding to a single Н-bond is observed. This corresponds to DA+(Н2O)3 molecular clusters and allows one to conclude that this cluster is stable relative to the others.

Role of gas–molecular cluster–aerosol dynamics in atmospheric new-particle formation

New-particle formation from vapors through molecular cluster formation is a central process affecting atmospheric aerosol and cloud condensation nuclei numbers, and a significant source of uncertainty in assessments of aerosol radiative forcing. While advances in experimental and computational methods provide improved assessments of particle formation rates from different species, the standard approach to implement these data in aerosol models rests on highly simplifying assumptions concerning gas–cluster–aerosol dynamics. To quantify the effects of the simplifications, we develop an open-source tool for explicitly simulating the dynamics of the complete particle size spectrum from vapor molecules and molecular clusters to larger aerosols for multi-compound new-particle formation. We demonstrate that the simplified treatment is a reasonable approximation for particle formation from weakly clustering chemical compounds, but results in overprediction of particle numbers and of the contribution of new-particle formation to cloud condensation nuclei for strongly clustering, low-concentration trace gases. The new explicit approach circumvents these issues, thus enabling robust model–measurement comparisons, improved assessment of the importance of different particle formation agents, and construction of optimal simplifications for large-scale models.

Changes in the new particle formation and shrinkage events of the atmospheric ions during the COVID-19 lockdown

Impacts of environmental changes at Pune, India during the lockdown period imposed due to the Covid-19 pandemic, on the characteristics of the atmospheric ions and the new particle formation (i.e. the formation of molecular clusters and their subsequent growth to larger sizes) and shrinkage events have been investigated. The increase in the small and big cluster ion concentrations and the decrease in intermediate ion concentrations observed during the lockdown period have been associated with the decrease in the aerosols and precursor gases, respectively. During the NPF events, the nucleation mode particles of both polarities grow in size. However, during the unique shrinkage events observed here, particles increase in concentration but do not grow in size during the morning-to-noon period and shrink in the noon-to-evening period during the lockdown period. Simultaneously, the concentration of particles of >25 nm decrease i during the morning hours and increase during the afternoon hours .On the shrinkage event days, solar irradiance is higher and relative humidity is lower throughout the day than on the NPF/no-event days. Occurrence of shrinkage events has been proposed to be associated with the change in saturation vapour pressure of different chemical species with temperature/solar irradiance.

Water/InP(001) from Density Functional Theory.

The interface between water and the In-rich InP(001) surface is studied by density functional theory with water coverage ranging from single molecules to multiple overlayers. Single molecules attach preferably to three-fold coordinated surface In atoms. Water dissociation is energetically favorable but hindered by an energy barrier that decreases with increasing water coverage. There is an attractive interaction between InP adsorbed water molecules that leads to the formation of molecular clusters and complete water films for water-rich preparation conditions. Water films on InP are stabilized by anchoring to surface-bonded hydroxyl groups. With increasing thickness, the water films resemble the structural properties of ice Ih. The oxygen and hydrogen evolution reactions on InP are characterized by overpotentials of the order of 1.7–1.8 and 0.2–0.3 eV, respectively. While the calculated bulk positions of the InP band edges are outside the range of the redox potentials for oxygen and hydrogen evolution within local DFT, the situation is different at the actual interface: Here, the interface dipole lifts the InP valence band maximum above the redox potential for oxygen evolution and favors hydrogen evolution.