An analytical approach to evaluate effective coefficients of 1–3 piezoelectric composites

In this paper, a micromechanics method is developed to evaluate effective coefficients of piezoelectric fiber-reinforced composites. An exact solution is derived for effective elastic, piezoelectric and dielectric coefficients of such piezocomposites subjected to the applied load in the direction transverse to the fiber orientation. Simultaneously, based on finite element method, a numerical study is performed on a representative volume element of such piezo composite containing fiber in square packing arrangement. The finite element method provides a numerical solution to evaluate effective elastic, piezoelectric and dielectric coefficients for discrete volume fraction of fiber, the range being 0.1–0.6 for this study. The results are interpolated to understand the overall behavior of such piezocomposites. The results obtained from the micromechanics method and the finite element method are compared with the results obtained from other models based on strength of materials method given in the literature. It is observed that the method developed in this study provides better results for effective coefficients susceptible to fiber packing arrangements.

Crystal structure and self-assembly on graphite of a pyrazolo[1,5-c]pyrimidine derivative

The crystal structure of the heterocyclic compound 2-(4-methoxyphenyl)-7-phenylpyrazolo[1,5-c]pyrimidine, C19H15N3O, has been determined and its self-assembly on the surface of graphite has been examined using atomic force microscopy (AFM). The title compound crystallized in the monoclinic space group P21/c, with two independent molecules in the asymmetric unit. The packing of the L-shaped molecules in the crystal is governed by arene interactions, in the absence of any conventional hydrogen-bonding interactions. The packing arrangement reveals four types of dimeric motifs stabilized by π–π and C—H...π interactions. At low coverage, molecules assemble into long needle-like islands on the graphite surface. High-resolution AFM images reveal that the molecules interact through weak noncovalent interactions between the aromatic H atoms and the methoxy O atoms.

COMPACT: Concurrent or Ordered Matrix-Based Packing Arrangement Computation Technique

Despite their versatility in treating irregular geometries, the raster methods have received limited attention in solving packing problems involving rotatable objects. In addition, raster approximation allows the use of unique performance metrics and indirect consideration of constraints, which have not been exploited in the literature. This study presents the Concurrent or Ordered Matrix-based Packing Arrangement Computation Technique (COMPACT). The method allows the objects to be rotated by arbitrary angles, unlike the right-angled rotation restrictions imposed in many existing packing optimization studies based on raster methods. The raster approximations are obtained through loop-free operations that improve efficiency. Additionally, a novel performance metric is introduced, which favors efficient filling of the available space by maximizing the overall contact within the domain. Moreover, the objective functions are exploited to discard the overlap and overflow constraints and enable the use of unconstrained optimization methods. The results of the case studies demonstrate the effectiveness of the proposed technique.

Counterion Effect and Isostructurality in a Series of Ag(I) Complexes Containing a Flexible, Imidazole Based Dipodal Ligand

The crystal structures of a series of Ag(I) complexes with 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene (L) and the counterions BF4− (1), PF6− (2), ClO4− (3), and CF3SO3− (4) were analysed to determine the effect of the latter on their formation. All resulting compounds crystallise in the non-centrosymmetric space group Cc of a monoclinic system and show the formation of cationic, polymeric 1D Ag(I) complexes. SCXRD analyses revealed that compounds 1–3 are isostructural, though 1 shows opposite handedness compared to 2 and 3, resulting in an inversed packing arrangement. The presence of the larger, elongated triflate counterion in 4 leads to a different ligand conformation, as well as different arrangements of the ligand in the cationic chain, and simultaneously results in a packing that exhibits fewer similarities with the remaining three compounds.

Rotaxane rings promote oblique packing and extended lifetimes in DNA-templated molecular dye aggregates

Molecular excitons play a central role in natural and artificial light harvesting, organic electronics, and nanoscale computing. The structure and dynamics of molecular excitons, critical to each application, are sensitively governed by molecular packing. Deoxyribonucleic acid (DNA) templating is a powerful approach that enables controlled aggregation via sub-nanometer positioning of molecular dyes. However, finer sub-Angstrom control of dye packing is needed to tailor excitonic properties for specific applications. Here, we show that adding rotaxane rings to squaraine dyes templated with DNA promotes an elusive oblique packing arrangement with highly desirable optical properties. Specifically, dimers of these squaraine:rotaxanes exhibit an absorption spectrum with near-equal intensity excitonically split absorption bands. Theoretical analysis indicates that the transitions are mostly electronic in nature and only have similar intensities over a narrow range of packing angles. Compared with squaraine dimers, squaraine:rotaxane dimers also exhibit extended excited-state lifetimes and less structural heterogeneity. The approach proposed here may be generally useful for optimizing excitonic materials for a variety of applications ranging from solar energy conversion to quantum information science.

Synthesis and structural characterization of hexa-μ2-chlorido-μ4-oxido-tetrakis{[4-(phenylethynyl)pyridine-κN]copper(II)} dichloromethane monosolvate

In the crystal structure of the title compound, [Cu4Cl6O(C13H9N)4]·CH2Cl2, the core molecular structure consists of a Cu4 tetrahedron with a central interstitial O atom. Each edge of the Cu4 tetrahedron is bridged by a chlorido ligand. Each copper(II) cation is coordinated to the central O atom, two chlorido ligands and one N atom of the 4-phenylethynylpyridine ligand. In the crystal, the molecules are linked by intermolecular C—H...Cl interactions. Furthermore, C—H...π and π–π interactions also connect the molecules, forming a three-dimensional network. Hirshfeld surface analysis indicates that the most important contributions for the packing arrangement are from H...H and C...H/H...C interactions.

6-Bromo-N-(3-(difluoromethyl)phenyl)quinolin-4-amine

A routine synthesis was performed to furnish the title compound which incorporates a versatile difluoromethyl group on the aniline substitution of a 4-anilinoquinoline kinase inhibitor motif. In addition, the small molecule crystal structure (of the HCl salt) was solved, which uncovered that the difluoromethyl group was disordered within the packing arrangement and also a 126.08(7)° out of plane character between the respective ring systems within the molecule. The compound was fully characterized with 1H/13C-NMR and high-resolution mass spectra (HRMS), with the procedures described.

Crystal structure and Hirshfeld surface analysis of (E)-N-(4-propyloxybenzylidene)benzo[d]thiazol-2-amine

The title compound, C17H16N2OS, was synthesized by a condensation reaction between 2-amino benzothiazole and 4-N-propoxybenzaldehyde. The benzo[d]thiazole ring system is nearly planar (r.m.s. deviation 0.0088 Å) and makes a dihedral angle of 3.804 (12)° with the phenyl ring. The configuration about the C=N double bond is E. In the crystal structure, pairs of C—H...N hydrogen bonds and C—H...π interactions link the molecules into inversion dimers with an R 2 2(16) ring motif. These dimers are additionally linked by weak π–π stacking interactions between the phenyl rings, leading to a layered arrangement parallel to (010). Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the packing arrangement are from H...H (47.9%) and C...H/H...C (25.6%) interactions.

Tris[N,N-bis(3,5-di-tert-butylbenzyl)dithiocarbamato-κ2 S,S′]-μ3-sulfido-tris-μ2-disulfido-triangulo-trimolybdenum(IV) iodide

The title compound, [Mo3(C31H46NS2)3S7]I, crystallizes on a threefold rotational axis in P31c (space group No. 159). The [Mo3S7(S2CN(CH2C6H3-3,5- t Bu2)2)3]+ cations are arrayed in sheets in the ab plane with interligand hydrophobic interactions between tert-butyl groups guiding the packing arrangement. These cations form stacks parallel to the c axis with a separating distance of 10.9815 (6) Å (the c axis length) between the Mo3 centroids. On the underside of the cluster, opposite the μ3-S2− ligand, the iodide counteranion forms close contacts of 3.166 (2) Å with the sulfur atoms of the μ2-S2 2− ligands. These contacts are less than the sum of the van der Waals radii of the atoms (1.8 and 2.1 Å for S and I, respectively), thus indicating an appreciable degree of covalency to the [Mo3S7(S2CN(CH2C6H3-3,5- t Bu2)2)3]+...I− interactions.

Synthesis, crystal structure at 219 K and Hirshfeld surface analyses of 1,4,6-trimethylquinoxaline-2,3(1H,4H)-dione monohydrate

The asymmetric unit of the title compound, C11H12N2O2·H2O, contains a molecule of 1,4,6-trimethyl-1,4-dihydroquinoxaline-2,3-dione and a solvent water molecule. Four atoms of the benzene ring are disordered over two sets of sites in a 0.706 (7):0.294 (7) ratio while the N-bound methyl groups are rotationally disordered with occupancy ratios of 0.78 (4):0.22 (4) and 0.76 (5):0.24 (5). In the crystal, molecules are linked by O—H...O and C—H...O hydrogen bonds into layers lying parallel to (10\overline{1}). The Hirshfeld surface analysis indicates that the most important contributions to the packing arrangement are due to H...H (51.3%) and O...H/H...O (28.6%) interactions. The molecular structure calculated by density functional theory is compared with the experimentally determined molecular structure, and the HOMO–LUMO energy gap has been calculated.