Crystal Packing Research Articles

Varied optical features and mechanofluorochromism in dicyanovinyl- vs. cyanoacrylicacid-linked twisted π-conjugates: A potential reusable platform for security applications

The dicyanovinyl-linked π-conjugates [DCV, =C(CN)2] are well identified as a stimuli/environment-sensitive fluorophore, while cyanoacrylic acid (CAA) -linked π-conjugates are hardly found. This study focuses on the diversity of solvatochromic, AIE- and mechanofluorochromic (MFC) features between DCV and CAA-linked conformationally twisted small π-conjugates. The creation of MFC-active smart molecules by tuning functionality has received considerable attention owing to its versatile applicability. While DCV-linked fluorophore TCN displays an impressive solvatofluorochromic property, CAA-linked analog TCNA showed no trend due to inter/intramolecular H-bonding. The TCN revealed AIE and a reversible MFC feature upon grinding with a significant bathochromic shift of 51 nm. Moreover, a 32 nm absorption shift was visually detected under ambient light after applying mechanical force (grinding). The non-AIEgen TCNA is emissive in the solid state but exhibited no emission/absorption shift after grinding. All the observed facts were supported by interpreting the molecular structures, crystal packing, powder X-ray diffraction data, and differential scanning calorimetric (DSC) studies. In addition, the DFT/TDDFT calculations were performed to support these outcomes. Finally, TCN is realized as a favorable platform for security writing/piezo patterning for anticounterfeiting applications.

Perusal on the role of DMF solvent and hydrogen bonding in the formation of 1D polymeric chains in mixed ligand Ni(II) complex as an anticancer agent: a computational approach

A novel mixed ligand Ni(II) metal complex has been investigated for the modification in structural conformation, coordination bond, and noncovalent interactions. The novel Ni(II) metal complex [Ni(TFPB)2(1,10-Ph)(DMF)] has been synthesized and structurally characterized, which featured six coordination with three bidentate ligands connected through oxygen and nitrogen atoms. The single-crystal X-ray analysis showed that the compound possessed octahedral geometry and C-H…F, C-H…O, and π…π intermolecular interactions resulting in the formation of supramolecular architecture contributed significantly towards the crystal packing and molecular stability. Hirshfeld surface analysis was carried out to validate various intermolecular interactions. Further, the 3D structural topologies were visualized using energy framework analysis. To explore the coordination stability and chemically reactive parameters of the novel Ni(II) complex, the electronic structure was optimized using density functional theory calculations. The natural bond orbital analysis revealed the various hyperconjugative interactions exhibited by the complex. In addition, the complex was screened for in silico studies to understand the antitumoricidal potential of the novel Ni(II) complex. Molecular docking studies were also performed against three targeted proteins (PDB ID: 6H0W, 6NE5, and 6E91) to investigate the binding mode and protein–ligand interactions. These results are further analyzed by molecular dynamic simulation to confirm the best possible interactions and stability in the active site of the targeted proteins with a simulation period of 100 ns. Communicated by Ramaswamy H. Sarma

The Hexacoordinate Si Complex SiCl4(4-Azidopyridine)2—Crystallographic Characterization of Two Conformers and Probing the Influence of SiCl4-Complexation on a Click Reaction with Phenylacetylene

4-Azidopyridine (1) and SiCl4 react with the formation of the hexacoordinate silicon complex SiCl4(4-azidopyridine)2 (2). Upon dissolving in warm chloroform, the complex dissociates into the constituents 1 and SiCl4 and forms back upon cooling. Depending on the cooling, two different crystalline modifications of 2 were obtained, which feature two different trans-conformers. Slow cooling to room temperature afforded conformer 2′, which features coplanar pyridine rings. Rapid cooling to −39 °C afforded crystals of conformer 2″, in which the planes of the pyridine ligands are nearly orthogonal to one another. Whereas 2′ resembles the molecular arrangement of various other known SiX4(pyridine)2 (X = halide) complexes, 2″ represents the first crystallographically confirmed example of a SiX4(pyridine)2 complex in this conformation. Conformers 2′ and 2″ were studied with 13C and 29Si solid state NMR spectroscopy. Their differences in 29Si chemical shift anisotropy, as well as energetic differences, were further investigated with computational analyses. In spite of the similar stabilities of the two conformers as isolated molecules, the crystal packing of 2″ is less stable, and its crystallization is interpreted as a kinetically controlled effect of seed formation. (3+2)-cycloaddition of 1 and phenylacetylene in toluene at 110 °C yields a mixture of 1-(4-pyridyl)-4-phenyl-1,2,3-triazole (1,4-3) and 1-(4-pyridyl)-5-phenyl-1,2,3-triazole (1,5-3) in approximate 1:2 molar ratio. The crystal structures of the two isomers were determined via X-ray diffraction. In chloroform (at 60 °C), this reaction is slow (less than 2% conversion within 4 h), but the presence of SiCl4 enhanced the rate of the reaction slightly, and it shifted the triazole isomer ratio to ca. 1:6 in favor of 1,5-3.

Never-Ending Story: New Cyclodextrin-Based Metal-Organic Framework Crystal Structures Obtained Using Different Crystallization Methods.

Six novel cyclodextrin (CD)-based metal-organic frameworks (MOFs) were synthesized using distinct crystallization methodologies. A modified vapor diffusion method is introduced for the first time, termed fast crystallization, which enables the rapid solid-state formation of MOF compounds. This innovative method yielded four of the newly synthesized MOFs. The crystal structures of five obtained frameworks were structurally characterized through single-crystal X-ray diffraction, while one, compound 5 (γ-CD-K-5), was additionally characterized as a bulk powder. Structural analysis revealed that two of the newly obtained MOFs, namely, compound 2 (α-CD-K-2) and compound 3 (α-CD-Rb-3), exhibited isostructural characteristics, forming a three-dimensional (3D) framework. Compound 1 (α-CD-K-1) shared the same space group as EVEGET (α-CD-K) and displayed the same framework type. Furthermore, the crystal packing of compound 4 (β-CD-K-4) closely resembled that of compound 1 and EVEGET, with the only distinction lying in the type of CD employed. Notably, compound 6 (γ-CD-K-6) incorporated an iodine ion with an occupancy of 0.2. To discern the intermolecular interactions within the obtained MOFs, the Hirshfeld surface was calculated using Crystal Explorer software.

Crystal structure, hydrogen bond patterns, Hirshfeld surface analysis, and topological studies (NCI) of 1,5,5-trimethyl-imidazolidine-2,4-dione; an organic compound with high symmetry crystallizing in the tetragonal space group I4/m

The title compound, 1,5,5-trimethyl-imidazolidine-2,4‑dione was characterized by FT-IR, 1H NMR, and 13C NMR spectroscopy techniques. The crystal structure was established by single-crystal X-ray diffraction. The powder X-ray powder diffraction analysis confirms the phase purity of the crystalline sample. The hydantoin with formula C6H10N2O2 crystallizes in the tetragonal space group I4/m (N°87), Z=8, and unit cell parameters a=15.554(2) Å, c=6.623(6) Å. This space group is very infrequent to find in purely organic molecules and is since, in the asymmetric unit, the hydantoin ring lies on a mirror plane m. The crystalline packing is stabilized by the formation of intermolecular interactions of the strong hydrogen bond type of the N–H···O between the neighboring hydantoin rings. In addition, the crystalline structure presents the formation of weaker unconventional hydrogen bonds of the C–H···O type. These hydrogen bonds give rise to the formation of 8, 24, and 36-membered ring-type supramolecular structures described by the graphs R22(8), R44(24), and R88(36), respectively, which govern the packing of the supramolecular structure of 1,5,5-trimethyl-imidazolidine-2,4‑dione.Hirshfeld surface analysis of the crystal structure shows that the most important contributions for the crystal packing are from H···H (58.3%) and H··O/O··H (34.0%) interactions, which indicate that van der Waals interactions are the dominant forces in the crystal packing. Energy framework calculations suggest that the contacts formed between molecules are slightly electrostatic.These intermolecular interactions were also investigated through topological analysis of the electron density (ρ) employing the NCI method. Experimental and theoretical results obtained for this new hydantoin compound suggest that N–H···O and C–H···O interactions play an important role in the stabilization of its supramolecular structure.

Structural Elucidation, In vitro and In silico Biological Evaluations of New Fluorinated Chalcone Derivatives for Potential Antioxidant Activity

Abstract: The newly synthesized fluorinated chalcone derivatives are observed to possess antioxidant potential. Two new fluorinated chalcone compounds were effectively synthesized using the Claisen- Schmidt condensation reaction and were recrystallized using the slow evaporation method. The single crystal structure of the compounds was determined and refined through the X-ray single crystal diffraction method. All compounds were subjected to computational structural characterization and Hirshfeld surface analysis. The compounds were then further characterized through the Ultravioletvisible (UV-Vis) spectroscopic study. The chalcone derivatives were further analysed with biological experimentation and simulation such as in vitro antioxidant (DPPH) assay, molecular docking and in silico ADMET study. The crystal packing revealed that the molecules in the compounds were linked together through the intermolecular C—H···O and C—H···π interactions. Hirshfeld surface analysis validated the presence of intermolecular interactions in crystal packing. The UV-Vis spectroscopic study revealed that the absorption wavelength of the compounds that range from 421.79 to 428.98 nm was within the visible region with the energy gap value of 2.58 to 2.62 eV. The DPPH assay disclosed weak antioxidant activity of both compounds (-31 to 20 %, 10000 μg/mL) compared to the standard ascorbic acid (94.5 %, 50 μg/mL). The binding energy of the docked complex inside the target protein, 2CAG was within the range of -7.3 to -7.5 kcal/mol. In the silico model, SwissADME predicted that the two compounds have overall good drug-like properties. Different substituents, more planar configuration and high intramolecular interactions in the crystal packing played their role in increasing the antioxidant activities, binding energy and drug likeliness of the synthesized compounds.

Synthesis, X-ray crystallographic, Hirshfeld, DFT study and interactions with TNFα receptors of chiral bisimines and diamines holding thiophene spacers

This paper outlines a facile synthesis of chiral bisimines R,R-(Thiophene-2,5-diyl)bis(N-(1-phenylethyl)methanimine) R,R-BI-1, S,S-(Thiophene-2,5-diyl)bis(N-(1-phenylethyl)methanimine) S,S-BI-2 and their reduced products R,R-(Thiophene-2,5-diyl)bis(N-(1-phenylethyl)methanamine) R,R-DA-1, S,S-(Thiophene-2,5-diyl)bis(N-(1-phenylethyl) methanamine) S,S-DA-2 holding thiophene spacers. The new derivatives were suitably characterized by microanalysis, standard spectroscopic techniques (1H, 13C NMR, FTIR, UV–visible absorption). Single crystal X-ray diffraction (SCXRD) method was used to study the supramolecular structures of R,R-BI-1 and S,S-BI-2, sustained primarily by CH…π intermolecular contacts which are well supported by molecular electrostatic potential (MESP). Quantification of short contacts existing in the crystal packing of these molecules was accomplished by Hirshfeld surface and fingerprint plots calculations. The geometry of all the molecules has been optimized by using a density functional theory calculation and the theoretical data were compared well with the experimental outcomes. Further, the calculated HOMO-LUMO band gaps for R,R-BI-1,S,S-BI-2,R,R-DA-1 andS,S-DA-2 (4.05–5.30 eV) suggests their non-conducting nature. Moreover, virtual screening of these nitrogenous compounds has been performed by molecular docking study to propose their potentials as biologically relevant molecules.

Mixed-ligand complex [Cu4(bpy)4(PO4)2(CO3)(H2O)2]: synthesis, crystal structure and biological properties

The interaction in the system {Сu(OAc)2·H2O–phytic acid–2,2`-bipyridine (bpy)} in an aqueous-methanol solution led to the formation of a molecular mixed-ligand tetranuclear complex [(Cu4(bpy)4(PO4)2(CO3 )(H2O)2]13H2O (I), the structure of which was established based on the results of an X-ray diffraction experiment (CCDC 2262998). According to X-ray diffraction data, the molecule contains four nonequivalent Cu2+ cations, which coordinate two phosphate anions (PO43-, remaining as a result transformation of the phytate cycle), four neutral bpy, two water molecules and one carbonate anion fragment (CO32-). The presence of a large number of solvate water molecules in the outer coordination sphere created a hydrogen-bonded framework involved in the stabilization of the crystal packing. Study of antimycobacterial activity of I in against the non-pathogenic strain Mycolicibacterium smegmatis showed its high bioeffectiveness.

High-temperature corrosion of phosphate completion fluid and corrosion inhibition method by membrane transformation

By analyzing the corrosion of phosphate completion fluid on the P110 steel at 170 °C, the high-temperature corrosion mechanism of phosphate completion fluid was revealed, and a corrosion inhibition method by membrane transformation was proposed and an efficient membrane-forming agent was selected. Scanning electron microscope (SEM) images, X-ray energy spectrum and X-ray diffraction results were used to characterize the microscopic morphology, elemental composition and phase composition of the precipitation membrane on the surface of the test piece. The effect and mechanism of corrosion inhibition by membrane transformation were clarified. The phosphate completion fluid eroded the test piece by high-temperature water vapor and its hydrolyzed products to form a membrane of iron phosphate corrosion product. By changing the corrosion reaction path, the Zn2+ membrane-forming agent could generate KZnPO4 precipitation membrane with high temperature resistance, uniform thickness and tight crystal packing on the surface of the test piece, which could inhibit the corrosion of the test piece, with efficiency up to 69.63%. The Cu2+ membrane-forming agent electrochemically reacted with Fe to precipitate trace elemental Cu on the surface of the test piece, thus forming a protective membrane, which could inhibit metal corrosion, with efficiency up to 96.64%, but the wear resistance was poor. After combining 0.05% Cu2+ and 0.25% Zn2+, a composite protective membrane of KZnPO4 crystal and elemental Cu was formed on the surface of the test piece. The corrosion inhibition efficiency reached 93.03%, which ensured the high corrosion inhibition efficiency and generated a precipitation membrane resistant to temperature and wear.

Synthesis and Crystallization of N-Rich Triazole Compounds

Among N-rich heterocycle backbone compounds, the triazoles building block received a lot of interest in several different academic and industrial studies and applications. This article outlines the process of synthesizing three different 1,2,4-triazole-based systems, commencing with 1,3-diaminoguanidine hydrochloride monohydrate as the starting material. The five novel crystal structures, Triaz1, Triaz2, Triaz3, Triaz4, and Triaz5, were characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Hirshfeld surface analysis was employed to explore the intermolecular interactions that are responsible for quantitative crystal packing. The synthesized compounds, with their elevated nitrogen content, serve as potential components for High-Energy-Density material science applications.

Synthesis, crystal structure and computational analysis of 2,7-bis-(4-chloro-phen-yl)-3,3-dimethyl-1,4-diazepan-5-one.

In the title compound, C19H20Cl2N2O, the seven-membered 1,4-diazepane ring adopts a chair conformation while the 4-chloro-phenyl substituents adopt equatorial orientations. The chloro-phenyl ring at position 7 is disordered over two positions [site occupancies 0.480 (16):0.520 (16)]. The dihedral angle between the two benzene rings is 63.0 (4)°. The methyl groups at position 3 have an axial and an equatorial orientation. The compound exists as a dimer exhibiting inter-molecular N-H⋯O hydrogen bonding with R 2 2(8) graph-set motifs. The crystal structure is further stabilized by C-H⋯O hydrogen bonds together with two C-Cl⋯π (ring) inter-actions. The geometry was optimized by DFT using the B3LYP/6-31 G(d,p) level basis set. In addition, the HOMO and LUMO energies, chemical reactivity parameters and mol-ecular electrostatic potential were calculated at the same level of theory. Hirshfeld surface analysis indicated that the most important contributions to the crystal packing are from H⋯H (45.6%), Cl⋯H/H⋯Cl (23.8%), H⋯C/C⋯H (12.6%), H⋯O/O⋯H (8.7%) and C⋯Cl/Cl⋯C (7.1%) inter-actions. Analysis of the inter-action energies showed that the dispersion energy is greater than the electrostatic energy. A crystal void volume of 237.16 Å3 is observed. A mol-ecular docking study with the human oestrogen receptor 3ERT protein revealed good docking with a score of -8.9 kcal mol-1.

Synthesis, Structure, and Hirshfeld Surface Analysis of tetrakis(N,N’-diethylthiourea)bis(isothiocyanato)nickel

The complex compound tetrakis(N,N’-diethylthiourea)bis(isothiocyanato)nickel or [Ni(detu)4(NCS)2] (denoted as UMCC-1) has been synthesized by reflux method in two different solvents namely acetone and methanol. This study aims to synthesize, characterize, and analyze the Hirshfeld Surface complex UMCC-1, which was obtained using the reflux method with the mole ratio of NiCl2: detu: KSCN is 1:2:4. Single crystals UMCC-1 in acetone and methanol are dark green in color with melting points of 135-137°C and conductivity of 66.4-84.4 µS. The FTIR absorption band analysis of the two crystals is very similar, ν(C S) detu 590 cm−1 and ν(C≡N) isothiocyanate 2119 cm−1. The refinement of the crystal structure from the single crystal XRD data shows that the two dark green crystals are a molecular type that has a distorted octahedral geometry with the same crystal lattice, monoclinic crystal lattice, P21/c1 space group (no.14), crystal lattice parameter a= 11.112(3) Å, b= 17.249(5) Å, c= 9.647(3) Å, and β= 100.785(10). However, the complex produced in acetone solvent has better refinement quality than methanol concerning %R= 3.27 and %R = 4.55, respectively. The UMCC-1 crystal shows intermolecular hydrogen bonds N-H---S(isothiocyanato) and intramolecular hydrogen bonds N-H---S(detu) with Hirshfeld Surface analysis showing a significant contribution of H---H (69.5%) on crystal packing.

The crystal structure of insecticidal protein Txp40 from Xenorhabdus nematophila reveals a two-domain unique binary toxin with homology to the toxin-antitoxin (TA) system

Txp40 is a ubiquitous, conserved, and novel toxin from Xenorhabdus and Photorhabdus bacteria, toxic to a wide range of insect pests. However, the three-dimensional structure and toxicity mechanism for Txp40 or any of its sequence homologs are not yet known. Here, we are reporting the crystal structure of the insecticidal protein Txp40 from Xenorhabdus nematophila at 2.08 Å resolution. The Txp40 was structurally distinct from currently known insecticidal proteins. Txp40 consists of two structurally different domains, an N-terminal domain (NTD) and a C-terminal domain (CTD), primarily joined by a 33-residue long linker peptide. Txp40 displayed proteolytic propensity. Txp40 gets proteolyzed, removing the linker peptide, which is essential for proper crystal packing. NTD adopts a novel fold composed of nine amphipathic helices and has no shared sequence or structural homology to any known proteins. CTD has structural homology with RNases of type II toxin-antitoxin (TA) complex belonging to the RelE/ParE toxin domain superfamily. NTD and CTD were individually toxic to Galleria mellonella larvae. However, maximal toxicity was observed when both domains were present. Our results suggested that the Txp40 acts as a two-domain binary toxin, which is unique and different from any known binary toxins and insecticidal proteins. Txp40 is also unique because it belongs to the prokaryotic RelE/ParE toxin family with a toxic effect on eukaryotic organisms, in contrast to other members of the same family. Broad insect specificity and unique binary toxin complex formation make Txp40 a viable candidate to overcome the development of resistance in insect pests.

Synthesis, crystal structure, DFT calculation and Hirshfeld surface analysis of N-(4-methyl phenyl)-2-(3-nitro-benzamido) benzamide

A new bis amide N-(4-methylphenyl)-2-(3-nitrobenzamide) benzamide was synthesized from a ring-opening reaction of 2-(3-nitrophenyl)-4H-benzoxazin-4-one, with 4-methyl aniline in a shorten reaction time (1.0 min) and characterized using different spectroscopic techniques (FT-IR, 1H-NMR, 13C-NMR) and single-crystal X-ray diffraction (XRD). In the crystal lattice, the molecules are linked by N–H···O and C–H···O hydrogen bonds. The Hirshfeld surface analysis mapped over shape index, curvedness indices, dnorm revealed strong H...H and H...O/O...H and intermolecular connections a key contributors to crystal packing structure. Density functional theory (DFT) calculations were applied with B3LYP/6-311G(d) level to provide theoretical data along with HOMO-LUMO electronic energy with the MEP map.
 KEY WORDS: Benzamide, Crystal structure, DFT calculation, Hirshfeld surface
 Bull. Chem. Soc. Ethiop. 2024, 38(1), 229-239. DOI: https://dx.doi.org/10.4314/bcse.v38i1.17

Self-assembly, virtual screening of a new cobalt complex: Synthesis, empirical, DFT calculations, biological activity investigations and identification of inhibitory activity on the main protease of COVID-19 and SARS-CoV2 by molecular docking strategy of (C6H6NF)2[Co(SCN)2

The present work undertakes the study of a new thiocyanic complex (C6H6NF)2[Co(SCN)2], a synergy between the two experimental and theoretical approach allows us to characterize and evaluate our crystal. (C6H6NF)2[Co(SCN)2] has been successfully synthesized at room temperature by slow evaporation and crystallized in monoclinic system with P21/c space group, in addition the X-ray powder diffraction to punctuate the obtention of a pure phase of the desired complex. Infrared spectrum was registered to revel the vibrational modes of the coordination compound. To highlight the optical properties, the UV–visible analysis was performed using a polar solvent. Thermal analyses were carried out to account for the thermal decomposition of complex. In order to gain insights into the role of weak molecular interactions in the complex that influence the self-assembly process and crystal packing, Hirshfeld surface analysis and DFT calculation were also performed. Furthermore, molecular docking and molecular dynamic simulations were performed for the compounds against different antibacterial targets to identify to which target the compounds show the best binding affinity. The MurF enzyme, which catalyzed the last cytoplasmic step of bacterial peptidoglycan synthesis, among the target was revealed to show better interactions with the enzyme and formed strong and stable intermolecular complex. Molecular docking analysis reveals that 1EPBN might display the inhibitory activity against coronavirus proteins (COVID-19 and SARS-CoV2).

Two adamantan-1-amine-based scaffolds: Synthesis, crystallographic synthons, TD/DFT calculations, in-depth molecular docking/ADME/T simulations, and shedding light on antibacterial/fungal activities

This work synthesized and structurally characterized the two adamantan-1-amine-based compounds, C10H18N2O3 (1) and C21H23NO (2), reacting with adamantan-1-amine, copper nitrate and 2-hydroxy-1-napthaldehyde in methanol. 1 has a nitrate blue salt-like structure, while 2 has a yellow azomethine-bonded Schiff base. X-ray crystal structure divulges 1–2 crystallized orthorhombic (P212121) and monoclinic space groups (P21/c). In 1, the three nitrate O’s form H bonds with three amine H from three different adamantylamine (N-H∙∙∙O bonds), 2 adopts a keto-imine tautomeric form, shifting the -H from hydroxyl -O to imine -N. The crystal packing stability in 1 result from the coulombic energy between a cation (protonated amine) and an anion (nitrate), whereas in 2, dispersive energy dominates the crystal packing. Hirshfeld surfaces (HS) and 2D fingerprint plots visualize supramolecular contacts. DFT simulated IR/NMR spectrum and UV–vis in methanol were compared with experimental using TDDFT calculations. The AIM, NCI and HOMO-LUMO profiles substantiate the H-bonds classification. Espinosa's equation predicts that the H-bond strength for intra-molecular (2) and intermolecular (1) are −40.69 and −17.07 kJ/mol. The Fukui function, ESP, and NLO explore chemical reactivity locations and polarization characteristics. ADME/T prediction evaluates the drug-like properties. Molecular docking predicted antimicrobial potency against bacteria and fungus, confirmed further by experiments.

A novel luminescent Ni(II) coordination compound for highly selective detection of acetylacetone, MnO4−, tetracycline and Ag+ in aqueous systems

A new Ni(II) compound [Ni(bim)2(H2O)4] (1,5-nds)·(H2O)0.51 (bim = benzimidazole, 1,5-nds-Na = disodium 1,5-naphthalenedisulfonate) was readily synthesized at room temperature. Although compound 1 is only a mononuclear compound, it is extended into a 2D supermolecule layer by hydrogen bonding interactions. Hirshfeld surfaces and fingerprint maps of compound 1 crystal packing were calculated to gather information on non-covalent interactions. Photoluminescence experiments showed that 1 not only possessed good solid-state fluorescence performance but also favorable fluorescence characteristics and stability in aqueous solutions, which can be exposed to acidic and alkaline environmental conditions (pH = 1–14) for a long time. Remarkably, compound 1 displayed outstanding anti-interference properties, high sensitivity, high quenching rate, and low limit of detection (LOD) against acetylacetone (acac), MnO4−, and tetracycline (TET) in water media via the Turn-Off effect (LOD:7.03 μM for acac, 2.92 μM for MnO4− and 0.65 μM for TET). Especially, compound 1 can also be used as a rare ratiometric fluorescent probe for the detection of Ag + down to the nM level. The exceptional multi-responsive performance suggested that compound 1 could be a potential multifunctional sensor. Furthermore, possible mechanisms were systematically investigated.

Crystal structure, Hirshfeld surface analysis and energy framework calculations of different metal complexes of a biphenol-based ligand: Role of solvent and transition metal ion

A new Pd(II) complex of the previously reported ligand N,N′-bis[(2,2′-dihydroxybiphen-3-yl)methyl]-N,N′-dimethylethylenediamine (L) was obtained from N,N-dimethylformamide/water. The roles in the solid state assembly of solvent molecules and molecular conformation were studied by comparing six complexes of L containing different metal centers (Ni(II), Cd(II), Cu(II), Pd(II)). Hirshfeld surface analysis, 2D fingerprint plots and energy frameworks calculations were used to investigate the intermolecular interactions within the crystal packings. Pd(II) and Ni(II) complexes arrange to form ribbons, while Cd(II) and Cu(II) complexes form 3D networks. Interactions between complexes and solvent molecules in the previously reported Pd(II) complex are replaced by complex-complex interactions in the new Pd(II) complex, while butanol and methanol are interchangeable in the interactions within the Ni(II) complexes. The present study suggested that the solid state assembly of these systems is mainly driven by the molecular conformation, that depends in turn by the metal ion involved, while the solvent only plays a minor role.

The use of polymorphic state modifiers in solid lipid microparticles: The role of structural modifications on drug release performance

This study investigates the correlation between the structural and release properties of solid lipid microparticles (MPs) of tristearin containing 5 % w/w of four different liquid additives used as crystal modifiers: isopropyl myristate (IM), ethyl oleate (EO), oleic acid (OA) and medium chain triglycerides (MCT). All additives accelerated the conversion of the unstable α-form of tristearin, formed after the MPs manufacturing, to the stable β-polymorph and the transformation was completed within 24 h (for IM and EO) or 48 h (for OA and MCT). The kinetic of polymorphic transition at 25 °C was investigated by simultaneous synchrotron SAXS/WAXS and DSC analysis after melting and subsequent cooling of the lipid mixture. After crystallization in the α-phase, additives accelerate the solid-solid phase transformation to β-tristearin. SAXS data showed that two types of structural modifications occurred on MPs during storage: compaction of the crystal packing (slight decrease in lamellar thickness) and crystal growth (increased number of stacked lipid lamellae). The release behavior of a model hydrophilic drug (caffeine) at two different amounts (15 % and 30 %) from MPs was studied in water and biorelevant media simulated the gastric and intestinal environment. It was particularly significant that the introduction of IM, EO and MCT were able to prolong the drug release in water, passing from a diffusion-based Higuchi kinetics to a perfect zero-order kinetic. Moreover, the overall release profiles were higher in biorelevant media, where erosion/digestion of MPs was observed. After 6 months, a moderate but statistically significant change in release profile was observed for the MPs with IM and EO, which can be correlated with the time-dependent structural alterations (i.e. larger average crystallite size) of these formulations; while MPs with OA or MCT displayed stable release profiles. These findings help to understand the correlation between release behavior, polymorphism and supramolecular‐level structural modification of lipid formulations containing crystal modifiers.

Crystal structure, Hirshfeld surface analysis, inter-molecular inter-action energies, energy frameworks and DFT calculations of 4-amino-1-(prop-2-yn-1-yl)pyrimidin-2(1H)-one.

In the title mol-ecule, C7H7N3O, the pyrimidine ring is essentially planar, with the propynyl group rotated out of this plane by 15.31 (4)°. In the crystal, a tri-periodic network is formed by N-H⋯O, N-H⋯N and C-H⋯O hydrogen-bonding and slipped π-π stacking inter-actions, leading to narrow channels extending parallel to the c axis. Hirshfeld surface analysis of the crystal structure reveals that the most important contributions for the crystal packing are from H⋯H (36.2%), H⋯C/C⋯H (20.9%), H⋯O/O⋯H (17.8%) and H⋯N/N⋯H (12.2%) inter-actions, showing that hydrogen-bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing. Evaluation of the electrostatic, dispersion and total energy frameworks indicates that the stabilization is dominated by the electrostatic energy contributions. The mol-ecular structure optimized by density functional theory (DFT) calculations at the B3LYP/6-311 G(d,p) level is compared with the experimentally determined structure in the solid state. The HOMO-LUMO behaviour was also elucidated to determine the energy gap.