Crystal structure of new formamidinium triiodide jointly refined by single-crystal XRD, Raman scattering spectroscopy and DFT assessment of hydrogen-bond network features
Ontology highlight
ABSTRACT:
SUBMITTER: Ordinartsev A
PROVIDER: S-EPMC8382056 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Interest in co-crystals formation has been constantly growing since their discovery, almost a century ago. Such success is due to the ability to tune the physical-chemical properties of the components in solid state by avoiding a change in their molecular structure. The properties influenced by the co-crystals formation range from an improvement of mechanical features and chemical stability to different solubility. In the scientific research area, the pharmacological field is undoubtedly one of those in which an expansion of the co-crystal knowledge can offer wide benefits. In this work, we described the crystalline structure of hexamethylenetetramine co-crystallized with the isophthalic acid, and we compared it with another co-crystal, showing the same components but different stoichiometry. To give a wider overview on the nature of the interactions behind the observed crystal packing and to rationalize the reasons of its formation, a computational analysis on such structures was carried out.
| S-EPMC8510214 | biostudies-literature
Project description:Lead halide perovskites are leading candidates for photovoltaic and light-emitting devices, owing to their excellent and widely tunable optoelectronic properties. Nanostructure control has been central to their development, allowing for improvements in efficiency and stability, and changes in electronic dimensionality. Recently, formamidinium lead triiodide (FAPbI3) has been shown to exhibit intrinsic quantum confinement effects in nominally bulk thin films, apparent through above-bandgap absorption peaks. Here, we show that such nanoscale electronic effects can be controlled through partial replacement of the FA cation with Cs. We find that Cs-cation exchange causes a weakening of quantum confinement in the perovskite, arising from changes in the bandstructure, the length scale of confinement, or the presence of δH-phase electronic barriers. We further observe photon emission from quantum-confined regions, highlighting their potential usefulness to light-emitting devices and single-photon sources. Overall, controlling this intriguing quantum phenomenon will allow for its suppression or enhancement according to need.
| S-EPMC9245356 | biostudies-literature
Project description:A long-lived hot carrier population is critical in order to develop working hot carrier photovoltaic devices with efficiencies exceeding the Shockley-Queisser limit. Here, we report photoluminescence from hot-carriers with unexpectedly long lifetime (a few ns) in formamidinium tin triiodide. An unusual large blue shift of the time-integrated photoluminescence with increasing excitation power (150?meV at 24?K and 75?meV at 293?K) is displayed. On the basis of the analysis of energy-resolved and time-resolved photoluminescence, we posit that these phenomena are associated with slow hot carrier relaxation and state-filling of band edge states. These observations are both important for our understanding of lead-free hybrid perovskites and for an eventual future development of efficient lead-free perovskite photovoltaics.
| S-EPMC5770436 | biostudies-literature
Project description:A Surface-Enhanced Raman Scattering (SERS) spectrum of 4-cyanopyridine (4CNPy) was recorded on silver plasmonic nanoparticles and analyzed by using Density Functional Theory (DFT) calculations. Two simple molecular models of the metal-4CNPy surface complex with a single silver cation or with a neutral dimer (Ag+-4CNPy, Ag2-4CNPy), linked through the two possible interacting sites of 4CNPy (aromatic nitrogen, N, and nitrile group, CN), were considered. The calculated vibrational wavenumbers and intensities of the adsorbate and the isolated species are compared with the experimental Raman and SERS results. The analysis of the DFT predictions and the experimental data indicates that 4CNPy adsorbs preferentially on neutral/charged active sites of the silver nanoparticles through the nitrogen atom of the aromatic ring with a perpendicular orientation.
| S-EPMC6780094 | biostudies-literature
Project description:At a temperature of 100 K, CH5N2+·I- (I), crystallizes in the monoclinic space group P21/c. The formamidinium cation adopts a planar symmetrical structure [the r.m.s. deviation is 0.002 Å, and the C-N bond lengths are 1.301 (7) and 1.309 (8) Å]. The iodide anion does not lie within the cation plane, but deviates from it by 0.643 (10) Å. The cation and anion of I form a tight ionic pair by a strong N-H⋯I hydrogen bond. In the crystal of I, the tight ionic pairs form hydrogen-bonded zigzag-like chains propagating toward [20-1] via strong N-H⋯I hydrogen bonds. The hydrogen-bonded chains are further packed in stacks along [100]. The thermal behaviour of I was studied by different physicochemical methods (thermogravimetry, differential scanning calorimetry and powder diffraction). Differential scanning calorimetry revealed three narrow endothermic peaks at 346, 387 and 525 K, and one broad endothermic peak at ∼605 K. The first and second peaks are related to solid-solid phase transitions, while the third and fourth peaks are attributed to the melting and decomposition of I. The enthalpies of the phase transitions at 346 and 387 K are estimated as 2.60 and 2.75 kJ mol-1, respectively. The X-ray powder diffraction data collected at different temperatures indicate the existence of I as the monoclinic (100-346 K), ortho-rhom-bic (346-387 K) and cubic (387-525 K) polymorphic modifications.
| S-EPMC5382624 | biostudies-literature
Project description:Bufotenine (5-hydroxy-N,N-dimethyltryptamine) is a natural tryptamine derivative with hallucinogenic activity. In this paper, we present novel chemical and molecular conformational analyses of bufotenine based on an experimental and theoretical approach integrating surface-enhanced Raman scattering (SERS) and density functional theory (DFT). For the first time, low concentrations of bufotenine in acetonitrile solutions were analyzed by SERS using two types of silver nanoparticle substrates synthesized via one- or two-step reduction processes. The vibrational characteristics of this molecule were verified by molecular dynamics simulations of Raman bands based on DFT. Here we demonstrate the potential of this integrated approach for the identification of bufotenine, a prominent hallucinogenic agent, establishing an innovative rapid and accurate sensing and characterization method of the identification of controlled substances at trace amounts.
| S-EPMC9251765 | biostudies-literature
Project description:The exo⇔endo isomerization of 2,5-dimethoxybenzaldehyde was theoretically studied by density functional theory (DFT) to examine its favored conformers via sp2-sp2 single rotation. Both isomers were docked against 1BNA DNA to elucidate their binding ability, and the DFT-computed structural parameters results were matched with the X-ray diffraction (XRD) crystallographic parameters. XRD analysis showed that the exo-isomer was structurally favored and was also considered as the kinetically preferred isomer, while several hydrogen-bonding interactions detected in the crystal lattice by XRD were in good agreement with the Hirshfeld surface analysis calculations. The molecular electrostatic potential, Mulliken and natural population analysis charges, frontier molecular orbitals (HOMO/LUMO), and global reactivity descriptors quantum parameters were also determined at the B3LYP/6-311G(d,p) level of theory. The computed electronic calculations, i.e., TD-SCF/DFT, B3LYP-IR, NMR-DB, and GIAO-NMR, were compared to the experimental UV-Vis., optical energy gap, FTIR, and 1H-NMR, respectively. The thermal behavior of 2,5-dimethoxybenzaldehyde was also evaluated in an open atmosphere by a thermogravimetric-derivative thermogravimetric analysis, indicating its stability up to 95 °C.
| S-EPMC7767059 | biostudies-literature
Project description:The structures of the mono- and the dihalogenated N-unsubstituted 2-aminobenzamides were characterized by means of the spectroscopic (¹H-NMR, UV-Vis, FT-IR, and FT-Raman) and X-ray crystallographic techniques complemented with a density functional theory (DFT) method. The hindered rotation of the C(O)-NH₂ single bond resulted in non-equivalence of the amide protons and therefore two distinct resonances of different chemical shift values in the ¹H-NMR spectra of these compounds were observed. 2-Amino-5-bromobenzamide (ABB) as a model confirmed the presence of strong intramolecular hydrogen bonds between oxygen and the amine hydrogen. However, intramolecular hydrogen bonding between the carbonyl oxygen and the amine protons was not observed in the solution phase due to a rapid exchange of these two protons with the solvent and fast rotation of the Ar-NH₂ single bond. XRD also revealed the ability of the amide unit of these compounds to function as a hydrogen bond donor and acceptor simultaneously to form strong intermolecular hydrogen bonding between oxygen of one molecule and the NH moiety of the amine or amide group of the other molecule and between the amine nitrogen and the amide hydrogen of different molecules. DFT calculations using the B3LYP/6-311++G(d,p) basis set revealed that the conformer (A) with oxygen and 2-amine on the same side predominates possibly due to the formation of a six-membered intramolecular ring, which is assisted by hydrogen bonding as observed in the single crystal XRD structure.
| S-EPMC6155760 | biostudies-literature
Project description:Investigating group-IV-based photonic components is a very active area of research with extensive interest in developing complementary metal-oxide-semiconductor (CMOS) compatible light sources. However, due to the indirect band gap of these materials, effective light-emitting diodes and lasers based on pure Ge or Si cannot be realized. In this context, there is considerable interest in developing group-IV based Raman lasers. Nevertheless, the low quantum yield of stimulated Raman scattering in Si and Ge requires large device footprints and high lasing thresholds. Consequently, the fabrication of integrated, energy-efficient Raman lasers is challenging. Here, we report the systematic investigation of stimulated Raman scattering (SRS) in Ge nanowires (NWs) and axial Al-Ge-Al NW heterostructures with Ge segments that come into contact with self-aligned Al leads with abrupt metal-semiconductor interfaces. Depending on their geometry, these quasi-one-dimensional (1D) heterostructures can reassemble into Ge nanowires, Ge nanodots, or Ge nanodiscs, which are monolithically integrated within monocrystalline Al (c-Al) mirrors that promote both optical confinement and effective heat dissipation. Optical mode resonances in these nanocavities support in SRS thresholds as low as 60 kW/cm2. Most notably, our findings provide a platform for elucidating the high potential of future monolithically integrated, nanoscale low-power group-IV-based Raman lasers.
| S-EPMC7322725 | biostudies-literature
Project description:A series of nanocomposites based on polyamide (NL16, PA) filter membranes containing metal nanoparticles (NPs) have been prepared by filtration under reduced pressure of the metal colloids. The ensuing materials were then investigated as substrates for surface-enhanced Raman scattering (SERS) imaging studies envisaging the spectroscopic detection of vestigial organic pollutants dissolved in contaminated water. The organic dye crystal violet (CV) was used here as a model pollutant because it is a hazardous compound present in certain effluent waters. Moreover this compound is well-known for its strong SERS activity, which is clearly advantageous in the context of material development for SERS. Indeed, several preparative strategies were employed to prepare PA-based composites, and the impact on SERS detection was investigated. These include the use of chemical and morphological distinct plasmonic NPs (Ag, Au), a variable metal load and changing the order of addition of the analytical specimens. These studies demonstrate that the parameters employed in the fabrication of the SERS substrates have a strong impact on the Raman signal enhancement. The use of Raman imaging during the fabrication process allows establishing improvements that translate to better performances of the substrates in the analyte detection. The results have been interpreted by considering an integrated set of operational parameters that include the affinity of CV molecules to the substrate, amount and dispersion of NPs in the PA membranes, and the detection method. Noteworthy the use of SERS analysis assisted with Raman imaging allowed achieving a detection limit for CV as low as 100 aM in ultrapure water and 10 fM in real samples.
| S-EPMC6641606 | biostudies-literature