Intermolecular Connection Research Articles

Synthesis, structure, growth, characterization and quantum chemical studies on 2-amino-5-bromopyridinium trichloroacetate: A novel phasematchable organic NLO single crystal

Organic crystals have become excellent candidates towards nonlinear optical (NLO) applications as they possess superior second and third order optical nonlinearities and high electro-optic coefficients when compared with their inorganic counterparts. In this direction, 2-Amino-5-bromopyridinium trichloroacetate (2A5BPT), a new organic second-order nonlinear optical compound is synthesized and optical grade single crystals are formed utilizing a slow evaporation solution growth approach at room temperature while using methanol as the solvent. Single crystal X-ray diffraction study shows that the title compound is assigned to monoclinic crystal system having non-centrosymmetric space group Cc. The crystal is transparent ( ̴ 85%) throughout the whole visible spectrum, according to the Ultraviolet-Visble (UV–Vis) spectra, with a cutoff wavelength of 367 nm and an optical energy band gap Eg of 3.32 eV. The crystal possesses good thermal stability. The compound has a 1.6 times greater powder second harmonic generation (SHG) efficiency than potassium dihydrogen phosphate (KDP). The phase matchability of the 2A5BPT is studied through particle size dependence of SHG. The intermolecular connection demonstrated by numerous inter contacts has been shown by a molecular Hirshfeld surface analysis of the crystal structure, and the related 2-dimensional finger print analysis further evaluates the individual contribution from each atom. In order to examine the first order hyperpolarizability, molecular electrostatic potential, and Highest occupied molecular orbital-Lowest unoccupied molecular orbital (HOMO-LUMO) energies, the quantum chemical calculations for the title molecule (2A5BPT) were carried out by density functional theory (DFT) utilizing the B3LYP/6–311++G(d,p) basis set. According to these results, the 2A5BPT crystal could be suitable for optoelectronic applications.

Electron Transport in Organic Photovoltaic Acceptor Materials: Improving the Carrier Mobilities by Intramolecular and Intermolecular Modulations

High carrier mobility is beneficial to increase the active-layer thickness while maintaining a high fill factor, which is crucial to further improve the light harvesting and organic photovoltaic efficiency. The aim of this Perspective is to elucidate the electron transport mechanisms in prototypical non-fullerene (NF) acceptors through our recent theoretical studies. The electron transport in A-D-A small-molecule acceptors (SMAs), e.g., ITIC and Y6, is mainly determined by end-group π-π stacking. Relative to ITIC, the angular backbone along with more flexible side chains leads to Y6 having a closer stacking and enhanced intermolecular electronic connectivity. For polymerized rylene diimide acceptors, to achieve high electron mobilities, they need to simultaneously increase intramolecular and intermolecular connectivity. Finally, finely tuning the π-bridge modes to enhance intramolecular superexchange coupling is essential to develop novel polymerized A-D-A SMAs.

Fluorine‐Containing Passivation Layer via Surface Chelation for Inorganic Perovskite Solar Cells

AbstractMinimizing surface defect is vital to further improve power conversion efficiency (PCE) and stability of inorganic perovskite solar cells (PSCs). Herein, we designed a passivator trifluoroacetamidine (TFA) to suppress CsPbI3−xBrxfilm defects. The amidine group of TFA can strongly chelate onto the perovskite surface to suppress the iodide vacancy, strengthened by additional hydrogen bonds. Moreover, three fluorine atoms allow strong intermolecular connection via intermolecular hydrogen bonds, thus constructing a robust shield against moisture. The TFA‐treated PSCs exhibit remarkably suppressed recombination, yielding the record PCEs of 21.35 % and 17.21 % for 0.09 cm2and 1.0 cm2device areas, both of which are the highest for all‐inorganic PSCs so far. The device also achieves a PCE of 39.78 % under indoor illumination, the highest for all‐inorganic indoor photovoltaic devices. Furthermore, TFA greatly improves device ambient stability by preserving 93 % of the initial PCE after 960 h.

Fluorine-Containing Passivation Layer via Surface Chelation for Inorganic Perovskite Solar Cells.

Minimizing surface defect is vital to further improve power conversion efficiency (PCE) and stability of inorganic perovskite solar cells (PSCs). Herein, we designed a passivator trifluoroacetamidine (TFA) to suppress CsPbI3-xBrx film defects. The amidine group of TFA can strongly chelate onto the perovskite surface to suppress the iodide vacancy, strengthened by additional hydrogen bonds. Moreover, three fluorine atoms allow strong intermolecular connection via intermolecular hydrogen bonds, thus constructing a robust shield against moisture. The TFA-treated PSCs exhibit remarkably suppressed recombination, yielding the record PCEs of 21.35% and 17.21% for 0.09 cm2 and 1.0 cm2 device areas, both of which are the highest for all-inorganic PSCs so far. The device also achieves a PCE of 39.78% under indoor illumination, the highest for all-inorganic indoor photovoltaic devices. Furthermore, TFA greatly improves device ambient stability by preserving 93% of the initial PCE after 960 h.

Phenolic Foams Toughened with Triethylene Glycol by In Situ Polymerization and Prepolymerization Processes

The current work presents the study of the toughening effect of in situ polymerization modification process (In-MP) and prepolymerization modification process (Pre-MP) on triethylene glycol (TEG)-modified phenolic foams (PFs). TEG in situ polymerization-modified phenolic resin (T-In-PR) and TEG prepolymerization-modified phenolic resin (T-Pre-PR) with different molecular structures have been synthesized by two processes using TEG as a modifier. The comparison of the molecular structure and properties of the resins shows that the molecular weight distribution of T-Pre-PR is uniform and its basic properties of resin are better than T-In-PR. The number of benzene ring linkage bridges in the T-Pre-PR structure increases from three to four, which can improve the toughness while stabilizing the intermolecular connection strength. The TEG-modified PFs prepared with TEG-modified phenolic resins exhibit excellent toughness. The fracture displacement of T-Pre-PF was 85.13% higher than those of ordinary PFs, and the pulverization rate was 55.85% lower than those of ordinary PFs. Compared with T-In-PF, the cell shapes of T-Pre-PF were uniform polygonal structures and formed a stable honeycomb-like structure. The cell size distribution of T-Pre-PF was more concentrated than those of T-In-PF and ordinary PFs, and the level of damage of cell wall was low. The maximum bending strength of T-Pre-PF was 0.263 MPa, and the maximum compression strength was 0.160 MPa, which were higher than those of T-In-PF. The findings demonstrate that Pre-MP is more suitable for the preparation of PFs with internal toughening modification by TEG than In-MP.

Supramolecular Synthon Identification in Azelaic Acid – Isonicotinamide

Supramolecular synthons are the smallest structural units that contain the information inherent in building large molecular assemblies. Here, we apply solid-state NMR methods for the identification of the synthon in a cocrystal of Azelaic acid [(CH2)7(COOH)2]– Isonicotinamide [C6H6N2O]. It is observed that the spin-lattice relaxation time of protons in the cocrystal is long, implying that the choice of experiments, particularly those that involve low-sensitivity nuclei, could be time consuming. It is noticed that the two dimensional 1H double quantum (DQ) – 1H single quantum (SQ) correlation experiment at very fast MAS (60 kHz) is able to provide information on proton-proton proximities that leads to an understanding of the synthon structure. Experiments such as the CP-Reverse CP and 1H–13C HETCOR have been used to obtain spectral assignment which was additionally confirmed by first-principle GIPAW NMR chemical shift calculations. Present study indicates the basic unit to be a heterosynthon in Azelaic acid (AZA) – Isonicotinamide (INIC) cocrystal formed by two different modes of intermolecular connectivity, viz. acid–pyridine and acid–amide hydrogen bonding interactions. The presence of a CH…O type bond involving a hydrogen of INIC is also indicated from the observation of a larger chemical shift of the corresponding proton. The experimental protocol presented in this paper is expected to be a useful tool for the estimation of the basic structural arrangement of the synthons in a rapid fashion.

Disordered Low Molecular Weight Spiropyran Exhibiting Photoregulated Adhesion Ability.

The functions of the materials composed of small molecules are highly dependent on their ordered molecular arrangements in both natural and artificial systems. Without ordered structure, small molecules hardly gain complicated functions, due to the absence of intermolecular covalent bond connection or strong network. Here, a low molecular weight spiropyran that could exhibit attractive photochromism and powerful adhesion property in disordered solid state is demonstrated. With maximum up to ∼8 MPa, the adhesion strength could be photoregulated in multiple levels, which also shows one-to-one correspondence to the specific color state. The working mechanism analysis on the photoregulated adhesion reveals that the isomer ratio of merocyanine form and the molecular packing density of spiropyran are the determining factors for the adhesion ability. The discovery of photoregulated adhesion from pure spiropyran provides a new strategy for developing functional materials by employing low molecular weight compounds.

Crystal Packing Analysis of Picric Acid, Phthalazone and their Cocrystal using Hirshfeld Computational Studies

In this paper we present the investigation of crystal packing of picric acid (PA), phthalazone (PZ) and theircocrystal phthalazone-picric acid (PA-PZ) using Hirshfeld surface computational analysis. The title molecules are synthesized, crystallized and three-dimensional structures are redetermined using XRD analysis. PA exhibit intermolecular hydrogen bonds O---H…N, O---H…O and intermolecular connection N---O...p. PZ shows N---H…O molecular interaction in it. O---H…O molecular contact has been noticed in PA-PZ. These intermolecular contacts within the crystal structure are quantified, evaluated and visualized in terms of 2D-finger print plots and Hirshfeld surfaces. In all crystal structures, O...H intercontact is common. The major contacts observed are O…H in PA and PA-PZ, H…H in PZ, respectively. In addition, electrostatic potential surface mappings are drawn on Hirshfeld surfaces for all the molecules

Growth, structural, Hirshfeld surface analysis, DFT validation on the crystal structure of 1, 10-Phenanthrolin-1-ium-5,6-dione perchlorate monohydrate

• A new molecular salt phendione perchlorate monohydrate has been synthesized using solvent intervened crystallization method. • Hirshfeld surface and 2D fingerprint plot analysis showed the percentage contributions of frail intermolecular connection and showed the enhanced molecular association. • DFT calculations exposed that PHDI had higher stability, electron affinity, ionization potential, and nucleophilicity. • Mulliken charges on phenanthroline ring in PHDI additionally affirmed the balanced arrangement with a slight contortion. The synthesis of molecular salts of 1,10-phenanthroline-5,6-dione (PHDI) with perchloric acid by solvent mediated crystallization. Single crystal X-ray diffraction (SCXRD) has been the most reliable technique in structural determination and for a better understanding of the structural properties of the compound. The molecular formula of the cocrystal is C 12 H 9 ClN 2 O 7 and Monoclinic Crystal system. The Space group P2(1)/n and unit cell dimensions a = 10.803(16) Å, α = 90°, b = 9.964(15) Å, β = 92.957(17)°, c = 12.184(18) Å, γ = 90° The Hirshfeld surface evaluation was led to examine intermolecular connections and related with 2D fingerprint plots revealing the overall contributions of the interactions present in the crystal design. Quantum chemical evaluations giving electron-density plots of HOMO and LUMO molecular orbitals and molecular electrostatic potentials (MEP) were also computed, both with the DFT/B3LYP/6–311 G++(d,p) basis set.

Cluster Identification Using Modularity Optimization to Uncover Chemical Heterogeneity in Complex Solutions.

Structural heterogeneity is commonly manifested in solutions and liquids that feature competition of different interparticle forces. Identifying and characterizing heterogeneity across different length scales requires multimodal experimental measurement and/or the application of new techniques for the interrogation of atomistic simulation data. Within the latter, the parsing of networks of interparticle interactions (chemical networks) has been demonstrated to be a valuable tool for identifying subensembles of chemical environments. However, chemical networks can adopt a wide variety of topologies that challenge generalizable methods for identifying heterogeneous behavior, and few network analysis algorithms have been proposed for multiscale resolution. In this study, we apply a method of partitioning using the graph theoretic concept of clusters and communities. Using a modularity optimization algorithm, the cluster partition creates subgraphs based on their relative internal and external connectivities. The methodology is tested on two soft matter systems that have significantly different network topologies so as to probe its ability to identify multiple scale features and its generalizability. A binary Lennard-Jones fluid is first examined, where one component causes subgraphs that have high internal network connectivity yet are still connected to the rest of the interparticle network of interactions. The impact of connectivity and edge weighting on the cluster partition is investigated. In the second system, hierarchically organized molecular structures comprised of hydrogen bonded water molecules are identified at a liquid/liquid interface. These structures have a much more sparse network with significantly varied internal connectivity that is a challenge to differentiate from the background hydrogen bonding network of water molecules at the instantaneous interface. The organized macrostructures are effectively isolated from the background network using the cluster partition, and a time-dependent implementation allows us to reveal their reactivity. These studies indicate that cluster partitioning based upon intermolecular network connectivity patterns is broadly generalizable, depending only on user-defined intermolecular connectivity, is operable across different length scales, and is extensible to the study of dynamic phenomena.

Chlorinated Spiroconjugated Fused Extended Aromatics for Multifunctional Organic Electronics.

The synthesis of a new molecule, SFIC-Cl, is reported, which features enhanced π-electron delocalization by spiroconjugation and narrowed bandgap by chlorination. SFIC-Cl is integrated into a single-crystal transistor (OFET) and organic light-emitting diode (OLED). The material demonstrates remarkable transport abilities across various solution-processed OFETs and retains efficient radiance in a near-infrared OLED emitting light at 700nm. Furthermore, the intermolecular multi-dimensional connection of SFIC-Cl enables the fabrication of a single-component large-area (2 × 2cm2 ) near-infrared OLED by spin-coating. The SFIC-Cl-acceptor-based solar cell shows excellent power conversion efficiency of 10.16% resulting from the broadened and strong absorption and well-matched energy levels. The study demonstrates that chlorinated spiroconjugated fused systems offer a novel direction toward the development of high-performance organic semiconductor materials for hybrid organic electronic devices.

Effect of micro‐aggregation behavior on the salt tolerance of polymer solutions

AbstractPolymer solution for oil displacement is mostly used in the middle and late stage of water flooding reservoir development, and reservoir groundwater conditions are often one of the main conditions restricting polymer application. Therefore, it is necessary to develop salt tolerance of polymer solutions with different aggregation behaviors, so as to facilitate the synthesis and optimization of suitable polymer systems. The differences in the micro‐aggregation behavior of three polymers with different molecular structures were explored. On this basis, the effects of divalent metal cations on the properties of the polymer solutions were analyzed by assessing the micro‐aggregation behavior, apparent viscosity, hydrodynamic size, and shear rheological characteristics. The results showed that the linear partially hydrolyzed polyacrylamide (HPAM) was seriously affected by divalent cations, and the viscosity decreased obviously. The aggregation behavior of the polymer changed by hydrophobic association can enhance the salt tolerance of the solution. The hydrophobically modified partially hydrolyzed polyacrylamide (HMPAM) with “chain beam” aggregation behavior has strong intermolecular connection, which enables it to withstand the content of calcium and magnesium ions of 1100 mg l−1. When the content of calcium and magnesium ions exceeds 600 mg l−1, dendritic hydrophobically associating polymer (DHAP) will destroy the interaction between molecular chains, resulting in the decrease of apparent viscosity and hydrodynamic size. For polymer flooding in high‐salinity reservoir, salt tolerant polymer system can be constructed by optimizing molecular weight and hydrophobic group content.

Characterization of Specific Ion Effects on PI(4,5)P2 Clustering using Molecular Dynamics Simulations and Graph-Theoretic Analysis

Numerous cellular functions mediated by phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) involve clustering of the lipid as well as co-localization with other lipids. Although the cation-mediated electrostatic interaction is regarded as the primary mechanism for PI(4,5)P2 clustering, the ion-specific nature of the intermolecular network formation makes it challenging to characterize the clustering. Here we use all-atom molecular dynamics (MD) simulations and graph-theoretic analysis to gain insight into the clustering. MD simulations reveal that the strong cation-headgroup interactions preferentially occur between specific pairs of cations (i.e., Ca2+, Na+, and K+) and phosphate groups (i.e., P1, P4, and P5, attached to C1, C4 and C5 carbon of the headgroup, respectively), in line with Collins's law of matching water affinities (LMWA). In the Ca2+/Na+/K+ mixture, Ca2+ preferentially binds to P4 and P5 while K+ penetrates deeper into the headgroup region toward P1; Na+ is attracted to both P1 and P4/P5. These specific ion interactions lead to the characteristic PI(4,5)P2 network connectivity and clustering patterns. The intermolecular connectivity was analyzed using basic graph-theoretic measures including degree distribution and clustering coefficient, while the clustering patterns were characterized via graph entropy measures.

Syntheses, structures and properties of three novel Cu(Ⅱ) coordination compounds based on 4,4′-oxybisbenzoic acid

Three Cu(Ⅱ) coordination compounds (CCs) with 4,4′-oxybisbenzoic acid (H2OBBA), {Cu3(OBBA)2(NH3)4}n (1), {Cu(OBBA)0.5(NH3)}n (2), {Cu2(OBBA) (NH3) (OH)}n (3) were synthesized under the ammoniacal condition in mixed solvents and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis and Fourier transform infrared spectra. Crystallographic studies have shown that, CC 1 is a 1D wavy chain structure, while the intermolecular connection of hydrogen bonds made it a 2D layered structure; CC 2 is a 2D layered structure composed of a 1D wavy chain structure and the O–H⋯N hydrogen bonds of R (2)2 (12) hydrogen bond motifs; CC 3 forms a 3D supramolecular framework through OH−, OBBA ligand and hydrogen bonds, in which, OBBA ligand has two cyclic patterns: C–OM―O and C–O―M, O⋯H–N. It may be concluded that OBBA ligands and hydrogen bonds play important role in the formation of multiple architectures. The photoluminescence and thermal behavior were also studied.

Charge Transfer Platform and Catalytic Amplification of Phenanthroimidazole Derivative: A New Strategy for DNA Bases Recognition.

Research about DNA composition has been concentrated on DNA damage in the past few decades. However, it still remains a great challenge to construct a rapid, facile, and accurate approach for simultaneously monitoring four DNA bases, guanine (G), adenine (A), thymine (T), and cytosine (C). Herein, a novel electrochemical sensor based on phenanthroimidazole derivative, 2-(4-bromophenyl)-1-phenyl-1H-phenanthro[9,10-d]-imidazole (PPI), is successfully fabricated by a simple electrochemical method. The bromophenyl group in PI could expand their aromatic plane, induce the π-conjugated extension, and enhance the charge transfer and π-π interaction. The phenyl group at N1 position could regulate the intermolecular interaction, which could promote the possibility of intermolecular connection. The PPI polymer (poly(PPI)) with π-electron enriched conjugation architecture has been applied in simultaneous determination of G, A, T, and C in neutral solution by square wave voltammetry (SWV) method with well-separated peak potentials at 0.714, 1.004, 1.177, and 1.353 V, respectively. The sensor functionalized with poly(PPI) exhibits wide linear response for G, A, T, and C in the concentration ranges of 3-300, 1-300, 30-800, and 20-750 μM, respectively. With favorable selectivity, stability, and reproducibility, the sensor is successfully utilized to monitor four DNA bases in real samples, displaying a promising prospect for electrochemical sensing devices.

Charge Transport in Highly Heterogeneous Natural Carbonaceous Materials

AbstractNatural carbonaceous materials (NCMs) have recently emerged as promising organic semiconducting materials for electronics and catalysis, although the fundamental picture of charge transport within NCM systems is still incomplete. Morphologically, NCMs exhibit reminiscence of disordered organic solids, yet the experimental measurements demonstrate a transport regime that surprisingly follows Mott's formula derived for variable‐range hopping in inorganic noncrystalline materials. With ab initio and kinetic Monte Carlo simulations, a temperature scaling is revealed between the Gaussian‐defect model log(σ) ∼ T−2 typical for organic matter and the Mott‐like log(σ) ∼ T−1/4 for a wide spectrum of intermolecular connectivity. As dominant transport descriptors, energy levels and coupling strengths are screened among 30 small molecules with varying sizes, shapes, sp2/sp3 ratios, side chains, and functional groups. These analyses provide insight for the design of NCM electronics, and should also be applicable to disordered molecular materials in general.

VdW‐TSSCDS—An automated and global procedure for the computation of stationary points on intermolecular potential energy surfaces

AbstractWe present a generalization of the transition state search using chemical dynamics simulations (TSSCDS) methodology (discussed in a previous study) which allows the topographical characterization of intermolecular potential energy surfaces (IPES) for non‐covalently bound complexes (vdW‐TSSCDS). Starting from a single random input geometry, we show that vdW‐TSSCDS is able to globally and automatically locate stationary points of an IPES, even in limiting cases such as extremely flat regions or nontrivial topologies (eg, bifurcation points). The basic idea is the expression of the connectivity matrix in block structure, where diagonal blocks correspond to the isolated fragments and off‐diagonal blocks provide the intermolecular connectivity. To this end, we introduce a new definition of bound or not, in a non‐covalent sense, utilizing an extra set of van der Waals distances, which encompasses all kinds of non‐covalent distances. To discuss the use of the vdW‐TSSCDS method, we present a series of 2‐body van der Waals systems, namely, Ar‐Benzene (3D), N2‐Benzene (6D) and H2O‐Benzene (9D). Finally, we further illustrate its capabilities by presenting some applications for n‐body problems (n > 2), (H2O)2‐Benzene (12D) and (H2O)3‐Benzene (21D), as well as to a reactive, fully‐flexible, system (Benzene‐NO2)+ (39D) in which the simultaneous breaking/formation of both covalent and non‐covalent interactions takes place.

A comparative study of the atomic structures of Ge-doped As4S3 and P4Se3 molecular glasses

The structures of pseudo-binary PSe and AsS glasses with compositions close to the P4Se3 and As4S3 stoichiometry with a few atom %Ge doping were determined using Monte Carlo simulations constrained by density and x-ray scattering measurements. We find that these glasses consist predominantly of P4Se3 and As4S3 molecules. The Ge doping results in some important differences between the two glasses. The PSe glass displays significantly higher intermolecular connectivity via PSeGe linkages, consistent with the significantly higher glass transition temperature and lower fragility of this liquid compared to its AsS counterpart. We also speculate that a consequence of this difference in the intermolecular connectivity would be to delay any pressure-induced conversion from a molecular to a network structure for the Ge doped PSe glass compared to the Ge-doped AsS glass.

Impact of alkyl chain branching positions on molecular packing and electron transport of dimeric perylenediimide derivatives

Abstract Side chains play a critical role in tuning intermolecular interaction and charge transport in organic semiconductors. Here, we have systematically investigated the impact of branching positions of the alkyl side chains on the molecular packing and electron transport properties of a series of bay-linked dimeric perylenediimide (PDI) derivatives by atomistic molecular dynamics simulations in combination with charge transfer rate theory and kinetic Monte Carlo simulations. The results show that despite of different branching positions of the alkyl chains, π–π stacking is effectively inhibited for all the dimeric PDI derivatives. As the branching position moves away from the PDI backbone, the appearance of the alkyl atoms around the PDI backbone will first decrease and then increase. Correspondingly, the short contacts between the PDI moieties are first enhanced and then reduced. In particular, when the branching position is at the third carbon atom, the intermolecular connectivity becomes the most effective and the electron mobility is significantly increased by 2 times.

Preparation of Siloxane-Based Microporous Crystals from Hydrogen-Bonded Molecular Crystals of Cage Siloxanes.

Controlled assembly of siloxane-based building blocks provides a rational approach toward designed architectures of silica-based porous materials. Here, a non-hydrothermal method to prepare microporous crystals from cage-type oligosiloxanes is reported. The crystals formation occurs through an ordered assembly assisted by hydrogen bonds and subsequent intermolecular connection by silylation. Cage siloxanes with a double-four ring (D4R) structure were modified with dimethylsilanol groups. Intermolecular hydrogen bonding of the dimethylsilanol groups led to the formation of a pillared-layer structure consisting of D4R units. A new crystalline microporous material retaining the original ordered arrangement was realized by bridging adjacent cages within the crystals by direct silylation of the silanol groups with trichlorosilane. The use of this silylating agent created microporous crystals containing Si-H groups, proving the advantages of the proposed concept.