Search Results (12)

A series of novel salts of heterocyclic polyamines with 5-sulfosalicylic acid (C₄H₇N₄⁺)(C₇H₅O₆S⁻)∙2(H₂O) (1), (C₄H₆ClN₄⁺)(C₇H₅O₆S⁻)∙H₂O (2), (C₅H₈N₃⁺)(C₇H₅O₆S⁻)∙H₂O (3), (C₅H₇N₆⁺)(C₇H₅O₆S⁻)∙H₂O (4), (C₆H₁₄N₂²⁺)(C₇H₄O₆S²⁻)∙H₂O (5), and (C₁₄H₁₉N₂⁺)(C₇H₅O₆S⁻) (6) have been successfully synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction. Overall, compounds adopt a layered structure with aminium cations and 5-sulfosalicylic anions linked via water molecules. The solid-state architectures of these compounds are dominated by O(N,H)-H⋯O and N-H⋯N hydrogen bonds and stabilized by weak interconnects. C-Cl⋯π and S-O⋯π interactions, apart from π⋯π and C-H(O)⋯π, were reported. Diverse approaches were used to study the effect of substituents in the polyamines in solid-state arrangement. A Hirshfeld surface analysis, with associated 3D Hirshfeld surface maps and 2D fingerprint plots, molecular electrostatic potential, and energy frameworks were used to comprehensively investigate the nature and hierarchy of non-covalent interactions and inspect supramolecular differences. The contact enrichment ratio calculations provided deeper insight into the propensity of interconnects to influence crystal packing. The evaluation of the effects of H-bonding synthons resulting from different substituents in the polyamines on self-assemblies is also presented. In the context of crystal engineering, a specific intramolecular synthon via O-H⋯O observed in nearly all crystals can be employed in the pseudo-cyclic replacement strategy in the design of new molecules. Full article

This study presents a new 5-methoxy-1H-indole-2-carboxylic acid (MI2CA) polymorph investigated by single-crystal X-ray diffraction, infrared spectroscopy, and density functional theory (ωB97X-D) calculations employing two basis sets (6-31++G(d,p) and aug-cc-pVTZ). The compound crystallizes in the monoclinic system, space group P2₁/c (a = 4.0305(2) Å, b = 13.0346(6) Å, c = 17.2042(9) Å, β = 91.871(5)°, Z = 4). In the crystalline structure, the formation of cyclic dimers via double hydrogen bonds O−H⋯O between MI2CA molecules was observed. Interactions between the NH groups of the indole rings and the adjacent methoxy groups, as well as C–H⋯O contacts, significantly influence the spatial arrangement of molecules. The results from DFT calculations, including dimeric and trimeric structures, agree well with the experimental structural and spectroscopic data. Analysis of the infrared spectra confirms the conclusions drawn from X-ray diffraction studies and reveals differences between the IR spectra of the newly obtained polymorph and that reported earlier in the literature. This comprehensive study sheds some light on the MI2CA polymorphism and is important for a potential pharmacological applications of this compound. Full article

DFT-D3 calculations based on structural X-ray diffraction data obtained for 3-oxo-camphorsulfonyl imine (1), camphorsulfonyl chloride (2) and seven camphor sulfonimines (O₂SNC₁₀H₁₃NR, L¹−L⁷), from which L² (R=4-OHC₆H₄), L⁴ (R=4-ClC₆H₄) and L⁶ (R=3,5-(CH₃)₂C₆H₃) are synthesized and characterized in this work, provide information into the intra- and inter-molecular interactions with concomitant elucidation of the supramolecular arrangement of the compounds. The DFT-D3 calculations performed in small clusters of two or three molecular units reproduce the interactions observed via X-ray analyses, showing that, as a general trend, the structural arrangement of the molecules is driven by electronic rather than by packing parameters. In all compounds, the self-assembly of 3D structures involves the sulfonyl imine group (-NSO₂) either to establish hydrogen bonds through oxygen atoms or non-classic oxygen–aliphatic hydrogen or non-bonding interactions (NBIs), which also involve sulfonyl oxygen atoms. Interestingly, the camphor sulfonimine compounds (L², L³), having protic groups (R=C₆H₄X:X=OH, L² or X=NH₂, L³) at the aromatic imine substituents (=NR), present an extra π-π stacking, which is absent in the other compounds’ aromatic derivatives. The X-ray analysis shows that all the reported camphor sulfonimine compounds display the E configuration with respect to the imine substituent (R). The study of the redox behavior of the compounds by cyclic voltammetry enables insight into the solution properties of the compounds and the rationalization of the molecular interactions that stand in the solid and solution states. Camphor sulfonimine compounds (L) display appropriate binding atoms to coordinate transition metals. The results herein show that monodentate coordination through the nitrogen atom of the sulfonimine five-membered ring to the {Ag(NO₃)} metal center is favored. When this imine nitrogen atom is not itself involved in the organic framework, DFT-D3 calculations show that the complexation does not affect the non-covalent interactions that are reproduced in the MOF structure. Full article

Cycloarene molecules are benzene-ring-based polycyclic aromatic hydrocarbons that have been fused in a circular manner and are surrounded by carbon–hydrogen bonds that point inward. Due to their magnetic, geometric, and electronic characteristics and superaromaticity, these polycyclic aromatics have received attention in a number of studies. The kekulene molecule is a cyclically organized benzene ring in the shape of a doughnut and is the very first example of such a conjugated macrocyclic compound. Due to its structural characteristics and molecular characterizations, it serves as a great model for theoretical research involving the investigation of $\pi$ electron conjugation circuits. Therefore, in order to unravel their novel electrical and molecular characteristics and foresee potential applications, the characterization of such components is crucial. In our current research, we describe two unique series of enormous polycyclic molecules made from the extensively studied base kekulene molecule, utilizing the essential graph-theoretical tools to identify their structural characterization via topological quantities. Rectangular kekulene Type-I and rectangular kekulene Type-II structures were obtained from base kekulene molecules arranged in a rectangular fashion. We also employ two subcases for each Type and, for all of these, we derived ten topological indices. We can investigate the physiochemical characteristics of rectangular kekulenes using these topological indices. Full article

A supramolecular self-assembly of semiconducting polymers and small molecules plays an important role in charge transportation, performance, and lifetime of an optoelectronic device. Tremendous efforts have been put into the strategies to self-organize these materials. In this regard, here, we present the self-organization of terthiophene and its methyl alcohol derivative with 4,4′-bipyridine (44BiPy). An unexpected 2D layered organization of 5,5″-dimethyl-2,2′:5′,2″-terthiophene (DM3T) and 44BiPy was obtained and analyzed. Single-crystal X-ray diffraction analysis revealed that DM3T and 44BiPy consist of stacked, almost independent, infinite 2D layers while held together by weak hydrogen bonds. In addition to this peculiar supramolecular arrangement of these compounds, the investigation of their photophysical properties showed strong fluorescence quenching of DM3T by 44BiPy in the solid state, suggesting an efficient charge transfer. On the other hand, the methyl alcohol derivative of terthiophene, DM3TMeOH, organized in a closed cyclic motif with 44BiPy via hydrogen bonds. Full article

QTAIM and source function analysis were used to explore the non-covalent bonding in twelve different water clusters (H₂O)_n obtained by considering n = 2–7 and various geometrical arrangements. A total of seventy-seven O−H⋯O hydrogen bonds (HBs) were identified in the systems under consideration, and the examination of the electron density at the bond critical point (BCP) of these HBs revealed the existence of a great diversity of O−H⋯O interactions. Furthermore, the analysis of quantities, such as $\left|V\left(r\right)\right|/G\left(r\right)$ and $H\left(r\right)$, allowed a further description of the nature of analogous O−H⋯O interactions within each cluster. In the case of 2-D cyclic clusters, the HBs are nearly equivalent between them. However, significant differences among the O−H⋯O interactions were observed in 3-D clusters. The assessment of the source function (SF) confirmed these findings. Finally, the ability of SF to decompose the electron density (ρ) into atomic contributions allowed the evaluation of the localized or delocalized character of these contributions to ρ at the BCP associated to the different HBs, revealing that weak O−H⋯O interactions have a significant spread of the atomic contributions, whereas strong interactions have more localized atomic contributions. These observations suggest that the nature of the O−H⋯O hydrogen bond in water clusters is determined by the inductive effects originated by the different spatial arrangements of the water molecules in the studied clusters. Full article

Five host−guest trimesic-acid-based hydrogen-bonds framework compounds with different guests, namely [(TMA)₄·(TMB)₃] (1), [(TMA)₂·(DMB)_1.5] (2), [(TMA)₆·(MP)] (3), [(TMA)·(EP)] (4) and [(TMA)·(PP)] (5) (TMA = trimesic acid, TMB = 1,3,5-trimethoxybenzene, DMB = 1,4-dimethoxybenzene, MP = 4-methoxyphenol, EP = 4-ethoxyphenol and PP = 4-propoxyphenol), were obtained through co-crystallization, and were characterized by elemental analysis, infrared spectroscopy analysis, and thermogravimetric analysis. The trimesic acid molecules comprise a hydrogen bonding six-membered cyclic host network that is found in a two-dimensional arrangement in compounds 1 and 2, and in a nine-fold interpenetrated three-dimensional structure in compound 3. In compounds 4 and 5, the trimesic acid and EP/PP molecules form a hydrogen-bonded six-membered cyclic network, resulting in a one-dimensional chain structure through O−H…O hydrogen bonds. Full article

Single crystals of two achiral and planar heterocyclic compounds, C₉H₈H₃O(CA1) and C₈H₅NO₂ (CA4), recrystallized from ethanol, were characterized by single crystal X-ray analysis, respectively, and chiral crystallization was observed only for CA1 as P2₁2₁2₁ (# 19), whereas it was not observed for CA4P2₁/c (# 14). In CA1, as a monohydrate, the hydrogen bonds were pronounced around the water of crystallization (O4), and the planar cyclic sites were arranged in parallel to slightly tilted positions. On the other hand, an anhydride CA4 formed a dimer by hydrogen bonds between adjacent molecules in the crystal, which were aggregated by van der Waals forces and placed in parallel planar cyclic sites. Full article

Hydrogen-bonded heterocomplexes formed by POOH-containing acids (diphenylphosphoric 1, dimethylphosphoric 2, diphenylphosphinic 3, and dimethylphosphinic 4) are studied by the low-temperature (100 K) ¹H-NMR and ³¹P-NMR using liquefied gases CDF₃/CDF₂Cl as a solvent. Formation of cyclic dimers and cyclic trimers consisting of molecules of two different acids is confirmed by the analysis of vicinal H/D isotope effects (changes in the bridging proton chemical shift, δH, after the deuteration of a neighboring H-bond). Acids 1 and 4 (or 1 and 3) form heterotrimers with very strong (short) H-bonds (δH ca. 17 ppm). While in the case of all heterotrimers the H-bonds are cyclically arranged head-to-tail, ···O=P–O–H···O=P–O–H···, and thus their cooperative coupling is expected, the signs of vicinal H/D isotope effects indicate an effective anticooperativity, presumably due to steric factors: when one of the H-bonds is elongated upon deuteration, the structure of the heterotrimer adjusts by shortening the neighboring hydrogen bonds. We also demonstrate the formation of cyclic tetramers: in the case of acids 1 and 4 the structure has alternating molecules of 1 and 4 in the cycle, while in case of acids 1 and 3 the cycle has two molecules of 1 followed by two molecules of 3. Full article

A review of intramolecular hydrogen bonding in ortho-hydroxyaryl Schiff bases, ortho-hydroxyaryl Mannich bases, dipyrrins, ortho-hydroxyaryl ketones, ortho-hydroxyaryl amides, and 4-Bora-3a,4a-diaza-s-indacene (BODIPY) dyes with tautomeric sensors as substituents is presented in this paper. Ortho-hydroxy Schiff and Mannich base derivatives are known as model molecules for analysing the properties of intramolecular hydrogen bonding. The compounds under discussion possess physicochemical features modulated by the presence of strong intramolecular hydrogen bonds. The equilibrium between intra- and inter-molecular hydrogen bonds in BODIPY is discussed. Therefore, the summary can serve as a knowledge compendium of the influence of the hydrogen bond on the molecular properties of aromatic compounds. Full article

The n-paraphenylene family comprises chains of phenylene units linked together by C-C bonds that are between single- and double-bonded, and where n corresponds to the number of phenylene units. In this work, we compare the response of the optical properties of different phenylene arrangements. We study linear chains (LPP), cyclic systems (CPPs), and non-conjugated cyclic systems with two hydrogenated phenylenes (H₄[n]CPP). Particularly, the systems of interest in this work are [6]LPP, [12]- and [6]CPP and H₄[6]CPP. This work combines Raman and infrared spectroscopies with absorption and fluorescence (one- and two-photon excitations) measured as a function of pressure up to maximum of about 25 GPa. Unprecedented crystallographic pressure-dependent results are shown on H₄[n]CPP, revealing intramolecular π-π interactions upon compression. These intramolecular interactions justify the H₄[n]CPP singular optical properties with increasing fluorescence lifetime as a function of pressure. Full article

Prorocentrolides are members of the cyclic imine phycotoxins family. Their chemical structure includes a 26-membered carbo-macrocycle and a 28-membered macrocyclic lactone arranged around a hexahydroisoquinoline that incorporates the characteristic cyclic imine group. Six prorocentrolides are already known. However, their mode of action remains undetermined. The aim of the present work was to explore whether prorocentrolide-A acts on nicotinic acetylcholine receptors (nAChRs), using competition-binding assays and electrophysiological techniques. Prorocentrolide-A displaced [¹²⁵I]α-bungarotoxin binding to Torpedo membranes, expressing the muscle-type (α1₂β1γδ) nAChR, and in HEK-293 cells, expressing the chimeric chick neuronal α7-5HT₃ nAChR. Functional studies revealed that prorocentrolide-A had no agonist action on nAChRs, but inhibited ACh-induced currents in Xenopus oocytes that had incorporated the muscle-type α1₂β1γδ nAChR to their membranes, or that expressed the human α7 nAChR, as revealed by voltage-clamp recordings. Molecular docking calculations showed the absence of the characteristic hydrogen bond between the iminium group of prorocentrolide-A and the backbone carbonyl group of Trp147 in the receptor, explaining its weaker affinity as compared to all other cyclic imine toxins. In conclusion, this is the first study to show that prorocentrolide-A acts on both muscle and neuronal nAChRs, but with higher affinity on the muscle-type nAChR. Full article