Intermolecular Interactions In Molecular Crystals Research Articles

A transferable quantum mechanical energy model for intermolecular interactions using a single empirical parameter.

The calculation of intermolecular interactions in molecular crystals using model energies provides a unified route to understanding the complex interplay of driving forces in crystallization, elastic properties and more. Presented here is a new single-parameter interaction energy model (CE-1p), extending the previous CrystalExplorer energy model and calibrated using density functional theory (DFT) calculations at the ωB97M-V/def2-QZVP level over 1157 intermolecular interactions from 147 crystal structures. The new model incorporates an improved treatment of dispersion interactions and polarizabilities using the exchange-hole dipole model (XDM), along with the use of effective core potentials (ECPs), facilitating application to molecules containing elements across the periodic table (from H to Rn). This new model is validated against high-level reference data with outstanding performance, comparable to state-of-the-art DFT methods for molecular crystal lattice energies over the X23 set (mean absolute deviation 3.6 kJ mol-1) and for intermolecular interactions in the S66x8 benchmark set (root mean-square deviation 3.3 kJ mol-1). The performance of this model is further examined compared to the GFN2-xTB tight-binding model, providing recommendations for the evaluation of intermolecular interactions in molecular crystal systems.

Concerning virial-based estimations of strength of bonding intermolecular interactions in molecular crystals and supramolecular complexes

It is shown that the electronic virial-based correlation should be used to estimate bonding contributions to the rigidity of molecular vibrations in crystals.

Structural Elucidation, Hirshfeld Surface, FMO, Molecular electrostatic potential (MEP) and Fukui function analyses of Quinoline based Schiff base Compound

A quinoline-derived Schiff base ligand, namely 2,5-Dimethyl-N1,N4-bis((quinoline-4-yl)-methylene)benzene-1,4-diamine 1 was characterized by single crystal X-ray structural studies that included a thorough examination of visualizing and investigating intermolecular interactions in molecular crystals via the Hirshfeld surface. The crystal packing of 1 displays intermolecular π∙∙∙π stacking interactions, resulting in a one-dimensional array. The major role of π∙∙∙π stacking interactions in stabilizing the crystal is also supported by the pre-eminence of dispersion energy over the other components in interaction energy calculation and energy framework analysis. The electronic structure of the ligand computed at B3LYP/6-311++G(d,p) level shows a good correlation with the experimentally obtained structure. Additionally, the Fukui function is calculated to identify the electrophilic and nucleophilic active sites in the molecule.

Boosting ultralong organic phosphorescence performance by synergistic heavy-atom effect and multiple intermolecular interactions in molecular crystal

A feasible strategy through synergistic heavy-atom effect and methylation approach to suppress non-radiative pathway and accelerate ISC processes is demonstrated. As a result, efficient and long-lived phosphorescence is realized.

Diaquabis(5-methoxyindole-2-carboxylato)bis(3-picoline)nickel(II) Complex: Synthesis, Characterization, XRD, TGA, DFT and HSA

A new complex of diaquabis(5-methoxyindole-2-carboxylato)bis(3-picoline)nickel(II) (Ni(5-MeOI2CA)2(3-pic)2(H2O)2), was synthesized for the first time and characterized by elemental analysis, FT-IR and electronic spectroscopy (UV-Vis) and single-crystal X-ray diffraction (XRD) techniques. The thermal degradation of the Ni(II) complex was investigated using thermogravimetric and differential thermal analyses techniques in oxygen atmosphere. The molecular structure of the complex was determined by single crystal X-ray diffraction technique. Hirshfeld surface analysis (HSA) investigated the packing modes and intermolecular interactions in molecular crystals, as they provide a visual picture of intermolecular interactions. In addition, all computational studies at B3LYP/6-311++G(d,p) were carried out for theoretical characterization of Ni(II) complex. The optimized geometry results, which were well represented the X-ray data, were shown that the chosen of DFT/B3LYP/6-311++G(d,p) was a successful choice for title compound. After a successful optimization, FMOs, chemical activity, non-linear optical properties (NLO), molecular electrostatic potential (MEP), Mulliken population (MPA), natural population analyses (NPA), Fukui function analysis (FFA) and natural bond orbital analysis (NBO), which could not obtained by experimental ways, were calculated and investigated. The computed of net charges and chemical activity studies which helped to identifying the electrophilic/nucleophilic nature.

Intermolecular interactions in molecular crystals and their effect on thermally activated delayed fluorescence of helicene-based emitters

In crystals of donor–acceptor helicene molecules, thermally activated delayed fluorescence (TADF) is strongly enhanced by the presence of occluded hexane molecules.

Synthesis, Hirshfeld surface analysis, laser damage threshold, third-order nonlinear optical property and DFT computation studies of Dichlorobis(DL-valine)zinc(II): A spectroscopic approach

The organometallic crystal of Dichlorobis(DL-valine)zinc(II) was grown by solution growth method. The computed structural geometry, vibrational wavenumbers and UV–visible spectra were compared with experimental results. Hirshfeld surface map was used to locate electron density and the fingerprint plots percentages are responsible for the stabilization of intermolecular interactions in molecular crystal. The second-order hyperpolarizability value of the molecule was also calculated at density functional theory method. The surface resistance and third-order nonlinear optical property of the crystal were studied by laser induced surface damage threshold and Z-scan techniques, respectively using Nd:YAG laser with wavelength 532 nm. The open aperture result exhibits the reverse saturation absorption, which indicate that this material has potential candidate for optical limiting and optoelectronic applications.

CrystalExplorer model energies and energy frameworks: extension to metal coordination compounds, organic salts, solvates and open-shell systems.

The application domain of accurate and efficient CE-B3LYP and CE-HF model energies for intermolecular interactions in molecular crystals is extended by calibration against density functional results for 1794 molecule/ion pairs extracted from 171 crystal structures. The mean absolute deviation of CE-B3LYP model energies from DFT values is a modest 2.4 kJ mol-1 for pairwise energies that span a range of 3.75 MJ mol-1. The new sets of scale factors determined by fitting to counterpoise-corrected DFT calculations result in minimal changes from previous energy values. Coupled with the use of separate polarizabilities for interactions involving monatomic ions, these model energies can now be applied with confidence to a vast number of molecular crystals. Energy frameworks have been enhanced to represent the destabilizing interactions that are important for molecules with large dipole moments and organic salts. Applications to a variety of molecular crystals are presented in detail to highlight the utility and promise of these tools.

Intermolecular interactions in molecular crystals: what's in a name?

Structure-property relationships are the key to modern crystal engineering, and for molecular crystals this requires both a thorough understanding of intermolecular interactions, and the subsequent use of this to create solids with desired properties. There has been a rapid increase in publications aimed at furthering this understanding, especially the importance of non-canonical interactions such as halogen, chalcogen, pnicogen, and tetrel bonds. Here we show how all of these interactions - and hydrogen bonds - can be readily understood through their common origin in the redistribution of electron density that results from chemical bonding. This redistribution is directly linked to the molecular electrostatic potential, to qualitative concepts such as electrostatic complementarity, and to the calculation of quantitative intermolecular interaction energies. Visualization of these energies, along with their electrostatic and dispersion components, sheds light on the architecture of molecular crystals, in turn providing a link to actual crystal properties.

Exploration of Supramolecular Architecture in Complexes with 1-Substituted-1H-[1,2,3]-triazole-4-carboxylic Acid: Structural Elucidation and Hirshfeld Surface Analysis

Two new complexes [Cu(HL)2(H2O)2] (1) and [AgHL]n (2) (where H2L is 5-methyl-1-(1H-pyrazol-3-yl)-1H-1,2,3-triazole-4-carboxylic acid) have been synthesized at room temperature and structurally characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction. Intermolecular, compounds 1 displays a 2D network containing 10-number and 4-number rings forming by intermolecular hydrogen bond O–H···O. Complex 2 is a Ag(I) polymer and exists C–H···Ag interactions forming the 2D layers into supermolecule. Intermolecular interactions in molecular crystal of 2 was explored by hirshfeld surface analysis, and the 2D fingerprint plots reveal that the main intermolecular contact is N···H/H···N contact with proportion of 22.9 %.

Accurate and Efficient Model Energies for Exploring Intermolecular Interactions in Molecular Crystals.

The energy of interaction between molecules is commonly expressed in terms of four key components: electrostatic, polarization, dispersion, and exchange-repulsion. Using monomer wave functions to obtain accurate estimates of electrostatic, polarization, and repulsion energies along with Grimme's dispersion corrections, a series of energy models are derived by fitting to dispersion-corrected DFT energies for a large number of molecular pairs extracted from organic and inorganic molecular crystals. The best performing model reproduces B3LYP-D2/6-31G(d,p) counterpoise-corrected energies with a mean absolute deviation (MAD) of just over 1 kJ mol(-1) but in considerably less computation time. It also performs surprisingly well against benchmark CCSD(T)/CBS energies, with a MAD of 2.5 kJ mol(-1) for a combined data set including Hobza's X40, S22, A24, and S66 dimers. Two of these energy models, the most accurate and the fastest, are expected to find widespread application in investigations of molecular crystals.

Incisive probing of intermolecular interactions in molecular crystals: core level spectroscopy combined with density functional theory.

The α-form of crystalline para-aminobenzoic acid (PABA) has been examined as a model system for demonstrating how the core level spectroscopies X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine-structure (NEXAFS) can be combined with CASTEP density functional theory (DFT) to provide reliable modeling of intermolecular bonding in organic molecular crystals. Through its dependence on unoccupied valence states NEXAFS is an extremely sensitive probe of variations in intermolecular bonding. Prediction of NEXAFS spectra by CASTEP, in combination with core level shifts predicted by WIEN2K, reproduced experimentally observed data very well when all significant intermolecular interactions were correctly taken into account. CASTEP-predicted NEXAFS spectra for the crystalline state were compared with those for an isolated PABA monomer to examine the impact of intermolecular interactions and local environment in the solid state. The effects of the loss of hydrogen-bonding in carboxylic acid dimers and intermolecular hydrogen bonding between amino and carboxylic acid moieties are evident, with energy shifts and intensity variations of NEXAFS features arising from the associated differences in electronic structure and bonding.

Intermolecular interactions in molecular crystals and glasses

The local structure of materials may not be apparent from Bragg crystallography, but emerges naturally from refinement against a pair distribution function (PDF). In molecular systems, the most prominent features in the PDF are the low-r peaks corresponding to the intramolecular interactions, yet these features are often the least interesting. The domination of the PDF by intramolecular interactions makes it difficult in the case of molecular materials to investigate the more interesting intermolecular interactions. In particular, few amorphous framework materials or molecular glasses have been characterized in any detail. Using reverse Monte Carlo (RMC) refinement against total neutron and x-ray scattering data we have studied the intermolecular interactions in two families of molecular materials, each including both crystalline and glassy phases. To overcome the problem posed by intramolecular interactions prior chemical knowledge of the molecular structure is incorporated into the refinement using empirical intramolecular potentials. One family consists of three phases of ZIF-4, a metal-organic framework consisting of tetrahedrally coordinated Zn2+ ions connected by imidazolate rings. In this material, we identify the molecular motion responsible for the greater flexibility shown by the amorphous phase compared to two crystalline phases [1]. The other family consists of the isomeric molecules para- and ortho-terphenyl (PTP/OTP). OTP is a paradigmatic glass-former, with a critical cooling rate of less than 0.1 K/min. PTP, on the other hand, is a crystalline material that undergoes an order-disorder phase transition at 178 K. We have characterized these materials' flexibility with the aid of molecular dynamics simulations. Our results demonstrate that RMC refinement with appropriate intramolecular potentials is capable of elucidating the intermolecular interactions of molecular systems, revealing new structural details in glassy and amorphous structures.

Structural elucidation and contribution of intermolecular interactions in O-hydroxy acyl aromatics: Insights from X-ray and Hirshfeld surface analysis

An O-hydroxy acyl aromatics, namely 1,1′,1″-(2,4,6-trihydroxybenzene-1,3,5-triyl) triethanone (1) was synthesized and characterized by spectroscopic and single crystal X-ray structural studies with a detailed scrutiny of visualizing and exploring intermolecular interactions in molecular crystals through Hirshfeld surface. The crystal packing of (1) exhibits intermolecular π–π stacking interactions to generate a one-dimensional parallel stacked ribbon propagating along (001) direction. Hirshfeld surface analysis for visually analyzing intermolecular interactions in crystal structures employing molecular surface contours and 2D fingerprint plots have been used to scrutinize molecular shapes. Crystal structure analysis supported with the Hirshfeld surface and fingerprint plots enabled the identification of the significant intermolecular interactions.

Structures and lattice energies of molecular crystals using density functional theory: Assessment of a local atomic potential approach

Lattice parameters and lattice energies of twelve selected molecular crystals are computed by using density functional theory (DFT) with different treatments of dispersion correction, including the local atomic potential (LAP) and three popular DFT-D methods. Inclusion of LAPs improves the description of intermolecular interactions in molecular crystals over standard DFT calculations. The DFT+LAP approach provides accurate structural parameters and lattice energies that are comparable to the PBE-Grimme scheme. Our results suggest that the DFT+LAP approach is a promising alternative for efficient and accurate quantum simulations on molecular crystals and other systems involving noncovalent interactions.

Charge Density Analysis of Heterohalogen (Cl···F) and Homohalogen (F···F) Intermolecular Interactions in Molecular Crystals: Importance of the Extent of Polarizability

Experimental charge density distribution in 2-chloro-4-fluorobenzoic acid and 4-fluorobenzamide has been carried out using high resolution X-ray diffraction data collected at 100 K using Hansen-Coppens multipolar formalism of electron density. These compounds display short Cl···F and F···F interactions, respectively. The experimental results are compared with the theoretical charge densities using theoretical structure factors obtained from periodic quantum calculation at the B3LYP/6-31G** level. The topological features were derived from Bader’s “atoms in molecules” (AIM) approach. Intermolecular Cl···F interaction in 2-chloro-4-fluorobenzoic acid is attractive in nature (type II interaction) while the nature of F···F interactions in 4-fluorobenzamide shows indication of a minor decrease in repulsion (type I interaction), though the extent of polarization on the fluorine atom is arguably small.

Yadernyi magnitnyi rezonans v van-flekovskikh magnetikakh i mezhmolekulyarnye vzaimodeistviya v molekulyarnykh kristallakh i fazakh Shevryolya

Ядерный магнитный резонанс в ван-флековских магнетиках и межмолекулярные взаимодействия в молекулярных кристаллах и фазах Шеврёля, Габуда С.П., Козлова С.Г., Лундин А.Г.

Computational investigations of the influence of polymorphism on the lattice dynamics of molecular organic crystals

The teraHertz range (60 GHz 4 THz = 2-130 cm) is a relatively unexplored, but information-rich part of the vibrational spectrum of molecular crystals. The motions in this frequency range are at lower energies than most of the internal vibrations ofmolecules (e.g., bond stretching and angle bending), but correspond instead to translations and librations of molecules. Thus, spectroscopic and computational investigations of this frequency range are a source of information on the intermolecular interactions in molecular crystals. Lattice dynamics calculations are being developed within the crystal structure modelling program DMAREL[1-2], for the use of elaborate model intermolecular potentials. Such calculations have been performed to characterise the measured teraHertz spectra of several molecular organic crystals, correlating regions of the spectra to distortions of certain intermolecular interactions. One of the systems studied is the polymorphic pharmaceuticalmolecule carbamazepine, whose basic hydrogen bonding amide dimers remains unchanged between polymorphs (Figure).

Evaluation of Weak Intermolecular Interactions in Molecular Crystals via Experimental and Theoretical Charge Densities

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Evaluation of weak intermolecular interactions in molecular crystals via experimental and theoretical charge densities

Analysis of charge density distributions in molecular crystals has received considerable attention in the last decade both from high-resolution X-ray diffraction studies and from high-level theoretical calculations. An overview of the progress made in deriving one-electron properties, intermolecular interactions in terms of the Atoms in Molecule (AIM) approach (R.F.W. Bader. Atoms in Molecules-A Quantum Theory, Clarendon, Oxford (1990), R.F.W. Bader. J. Phys. Chem., A102, 7314 (1998)) is given with special emphasis on improvements in charge density models and development of both experimental and theoretical techniques to interpret and analyse the nature of weak intermolecular interactions. The significance of the derived results from the charge density of coumarin and its derivatives have been analysed to obtain insights into the nature of intermolecular C–H ··· O, C–H ··· π, π ··· π, C–H ··· S, and S ··· S contacts. The appearance of a ‘region of overlap’ to segregate hydrogen bonds from van der Waals interactions based on the criteria proposed by Koch and Popelier (U. Koch, P.L.A. Popelier. J. Phys. Chem., 99, 9747 (1995), P.L.A. Popelier. Atoms in Molecules. An Introduction, pp. 150–153, Prentice Hall, UK (2000)) and the identification of differences in energy surfaces in concomitant polymorphs of 3-acetylcoumarin are described.