Comparison of non-covalent interactions and spectral properties in 1-methyl-3-methylthio-5-phenyl-1,2,4-triazinium mono- and tetraiodide crystals

The reaction of 1-methyl-3-methylthio-5-phenyl-1,2,4-triazinium (MTPT) iodide with diiodine in a solution leads to monoiodide crystal structure that in excess of iodine gives the unusual tetraiodide anion with two central iodine atoms in disorder. The bonding within the anion has been characterized as I^–…I₂…I^–; the existence of the bound iodine molecule inside has been proven by the characteristic band in experimental and calculated Raman spectra. Non-covalent interactions of MTPT in considered crystal structures are different. Monoiodide anion as a strong electron donor allows the formation of the S…I chalcogen bonds that are absent in tetraiodide structure. The features of halogen bonds within the I₄^2– anion are also performed.

     

Synthesis and Characterisation of the Nitridocuprate(I) Nitride Carbodiimide (Sr6N)[CuN2][CN2]2

The strontium nitridocuprate(I) nitride carbodiimide has been successfully produced and characterised. Single crystals were grown in metal ampoules, utilising an alkali metal as a fluxing agent. Structural characterisation was conducted via single-crystal X-ray diffraction and the identity of the [CN₂]^2– anion as carbodiimide was confirmed by Raman spectroscopy. Diamagnetic behaviour over a large temperature range supports the copper(I) electronic state.     

Ramanspektrum und Bindungsdiskussion von matrixisoliertem,molekularem Siliciumdisulfid

Raman Spectrum and Bonding of Matrix Isolated, Molecular Silicon Disulfide By means of a reaction between the high-temperature molecules SiS and Si atoms within a methan matrix molecular SiS₂ is obtained, which has been characterized via the symmetric stretching mode at 514 cm^–1 in the Raman spectrum. SiS₂ and SiS are discussed with respect to multiple bonding by a comparison with the similar carbon sulfids CS and CS₂ on the basis of quantum chemical calculations including the results of vibrational spectroscopy.     

Micro-Raman Spectroscopy of Nanostructured Silver Sulfide

Nanostructured silver sulfide powder with an average particle size of about 45 nm, an acanthite α-Ag₂S monoclinic structure (space group P2₁/c), and nonstoichiometric composition Ag_1.93S has been synthesized by the chemical deposition method. The silver sulfide nanopowder has been studied by Raman spectroscopy. According to the Raman scattering data, heating the nanopowder with high-power laser radiation in air leads to photoinduced decomposition of the Ag_1.93S nanopowder to give silver metal. The Raman spectrum of the silver sulfide nanopowder shows a series of bands in the low-frequency range from 90 to 260 cm^–1 associated with vibrations of silver atoms, Ag–S bonds, and symmetric Ag–S–Ag longitudinal modes. Raman spectroscopy confirmed an acanthite monoclinic structure of synthesized silver sulfide nanopowder.     

Raman spectrum and secondary structure of the phage λ operator site OL1: evidence for multiple nucleoside conformations in an aqueous B-form DNA

The laser Raman spectrum of O_L1 has been obtained in the region 600–850 cm⁻¹ and the data have been interpreted in terms of different nucleoside conformations within the 17 base pair operator site. The O_L1 sequence, which is one of the tightest binding sites for the cI and Cro repressors of bacteriophage λ, displays several Raman conformation markers indicative of more than one backbone geometry for the same double-stranded DNA helix. Specific assignments for the Raman conformation markers are suggested by analogy with spectra of DNA single crystals and DNA fibers of known structure. Two Raman bands diagnostic of B-DNA backbone geometry are observed at 825 ± 3 and 838 ± 3 cm⁻¹, and may be due, respectively, to inequivalent conformations of GC and AT pairs. In addition, a weak band at 706 cm⁻¹ and a shoulder near 807 cm⁻¹ are consistent with a minor contribution from residues which assume the A-DNA backbone geometry or a structurally related configuration. The complex bandshape in the 650–700 cm⁻¹ interval, which is resolved into four peaks by Fourier deconvolution, is also consistent with the presence of multiple nucleoside conformers in O_L1 in physiological conditions.     

A New Chair‐shaped Conformation Containing HgHgOHgHgO: Synthesis and Structure of Hg4(L2)2(NO3)4 (L2 = morpholin‐4‐ylpyridin‐2‐ylmethyleneamine)

. The complex Hg₄(L²)₂(NO₃)₄ ( 1 ) (L² = morpholin‐4‐ylpyridin‐2‐ylmethyleneamine) has been synthesized and characterized by CHN analysis, IR, and UV/Vis spectroscopy. The crystal structure of 1 was determined using single‐crystal X‐ray diffraction. The crystal structure of 1 contains four mercury atoms, four nitrate anions (two terminal and two bridge ones) and two L² ligand molecules. A chair shape, six‐membered ring is formed with the sequence OHgHgOHgHg built from Hg–Hg dumbbells and oxygen atoms from the nitrate co‐ligands. In the crystal structure, the asymmetric unit of the compound is built up by one‐half of the molecule. It contains the Hg₂²⁺ moiety with a mercury–mercury bonded core, in which one diimine ligand is coordinated to one of the mercury atoms. The nitrate anions act as anisobidentate and bidentate ligands.     

Darstellung,spektroskopische Charakterisierung und Kristallstrukturen von [(C5H5N)2CH2][PtCl5(SCN)] und cis-[(C5H5N)2CH2][PtCl4(SCN)2]

Preparation, Spectroscopic Characterization, and Crystal Structures of [(C₅H₅N)₂CH₂][PtCl₅(SCN)] and cis -[(C₅H₅N)₂CH₂][PtCl₄(SCN)₂] By treatment of [PtCl₆]^2– with SCN^– in aqueous solution a mixture of chlorothiocyanatoplatinates(IV) is formed, from which [PtCl₅(SCN)]^2– and cis-[PtCl₄(SCN)₂]^2– have been separated by ion exchange chromatography on diethylaminoethyl cellulose. X-Ray structure determinations on single crystals of [(C₅H₅N)₂CH₂][PtCl₅(SCN)] ( 1 ) (tetragonal, space group P 4₃, a = 7.687(1), c = 29.698(4), Z = 4) and cis-[(C₅H₅N)₂CH₂][PtCl₄(SCN)₂] ( 2 ) (monoclinic, space group P 2₁/n, a = 11.2467(9), b = 15.0445(10), c = 11.3179(13), β = 92.840(9)°, Z = 4) show, that the thiocyanate groups are coordinated via S atoms with average Pt–S distances of 2.339 Å and Pt–S–C angles of 104.7° up to 107.1°. Using the molecular parameters of the X-ray determinations the low temperature (10 K) IR and Raman spectra have been assigned by normal coordinate analyses. The valence force constants of the S–Pt–Cl˙ axes are f_d(PtS) = 1.81 ( 1 ) and 1.87 ( 2 ), f_d(PtCl ^× ) = 1.77 ( 1 ) and 1.81 ( 2 ), of the Cl–Pt–Cl axes are f_d(PtCl) = 1.93 ( 1 ) and 1.90 mdyn/Å ( 2 ). The ¹⁹⁵Pt NMR spectra from dichlormethane solutions exhibit each one sharp signal at 3975.6 ( 1 ) and 3231.6 ppm ( 2 ), respectively.     

The Quasi‐Binary Acetonitriletriide Sr3[C2N]2

The first quasi‐binary acetonitriletriide Sr₃[C₂N]₂ has been synthesised and characterised. The nearly colourless crystals were obtained from the reaction of Sr metal, graphite, and elemental N₂, generated by decomposition of Sr(N₃)₂, in a sealed Ni ampoule with the aid of an alkali metal flux. The structure of this compound was analysed via single‐crystal X‐ray diffraction and the identity of the [C₂N]^3? anion was confirmed by Raman spectroscopy and further investigated by quantum‐chemical methods. Computed interatomic distances within the [C₂N]^3? anion strikingly match the obtained experimental data.     

The effects of isotopic substitution (H2OD2O) in the Raman spectra of strontium formate dihydrate single crystals

Polarized Raman spectra measured in the temperature range between 10–293K are reported for SFDH, SFDD single crystals and isotopically samples of Sr(HCOO)₂.2(H,D)₂O.AtT=293 K the uncoupled OD(H) stretching motions are observed in the range ν=2200–2600(3000–3500) cm⁻¹ Plausible assignments to the distinct crystallographically non equivalent H₂O(D₂O) molecular group are given. The investigation has been conducted to elucidate this situation as well as that the structural role of lattice water molecules in molecular crystals.     

Synthesis and crystal structure of diiodobis(thiourea)mercury (ii)-bis(diazafluoren-9-one)

The title compound, [HgI₂(CH₄N₂S)₂]·2C₁₁H₆N₂O, is comprised of the Hg(II)–thiourea complex and free 4,5-diazafluoren-9-one (DAFONE). The complex assumes a distorted tetrahedral geometry at mercury formed by two thiourea molecules and two I^? ions, the S–Hg–S angle [103.7°] being significantly smaller than S–Hg–I angles (115.2 and 114.3°). The complex and DAFONE molecules link to each other via hydrogen bonding to form a supramolecular structure. Significant π–π stacking is observed between neighboring DAFONE molecules.     

Study of alkali halide/FHF− systems at 10 – 290 K, 0 – 8 kBAR

The bifluoride ion FHF^?, (and FDF^?), has been substitutionally isolated within single crystal samples of several alkali halides. Infrared and Raman spectra of these crystals have been studied at variable temperature and pressure. The infrared absorptions are strong, whereas the Raman is weak. At low temperatures the bands are very sharp with halfwidths less than 1 cm^?1. On applying pressure, ^ν₃ increases in frequency whereas ^ν₂ decreases. On reducing temperature, ^ν₃ decreases in frequency whereas ^ν₂ increases. Hence the effect of volume contraction is overridden in the temperature dependent case. The deuterated spectra confirm that the bifluoride ion is well isolated within the alkali halide matrix.     

Extending the metal interface generality of surface-enhanced Raman spectroscopy: Underpotential deposited layers of mercury,thallium, and lead on gold electrodes

Surface-enhanced Raman (SER) spectra are reported for several adsorbates at underpotential deposited (upd) layers of mercury, thallium, and lead on an electrochemically roughened gold electrode. For upd mercury monolayers, SER bands were obtained for the surface-halide stretching mode, ν_M-X, of adsorbed chloride and bromide that are of comparable intensities to those observed on the unmodified gold substrate. The ν_M-X peak frequencies are downshifted by 15–24 cm⁻¹ on the former relative to the latter surface, consistent with a smaller extent of halide bond covalency on mercury. These spectral changes induced by upd formation could be reversed by anodic stripping of the mercury monolayer. Comparable results were also obtained by prior formation of the upd monolayer in a separate solution followed by electrode transfer rather than by deposition in the solution of interest. Satisfactory SER spectra at upd mercury are reported additionally for thiocyanate and pyridine, as are similar experiments for upd thallium and lead layers on gold. Of the above adsorbates, only pyridine yielded easily measurable SER spectra for these layers, having 2–3 fold smaller signal intensities than on unmodified gold. The SERS intensity decreases upon thallium, and lead upd formation exhibited both irreversible and reversible components. Differential capacitance-potential plots for upd mercury indicate some similarities to liquid mercury interfaces. The results indicate that overlayers on gold provide a means of extending SERS to metals that in themselves do not exhibit suitable Raman scattering enhancements.     

Unprecedented synthesis of 1,3-dimethylcyclobutadiene in the solid state and aqueous solution

Cyclobutadiene ( CBD ), the smallest cyclic hydrocarbon bearing conjugated double bonds, has long intrigued chemists because of its chemical characteristics. The question of whether the molecule could be prepared at all has been answered, but the parent compound and its unperturbed derivatives have eluded crystallographic characterization or synthesis “in water”. Different approaches have been used to generate and to trap cyclobutadiene in a variety of confined environments: a) an Ar matrix at cryogenic temperatures, b) a hemicarcerand cage enabling the characterization by NMR spectroscopy in solution, and c) a crystalline guanidinium–sulfonate–calixarene G₄C matrix that is stable enough to allow photoreactions in the solid state. In the latter case, the 4,6‐dimethyl‐α‐pyrone precursor, Me₂1 , has been immobilized in a guanidinium–sulfonate–calixarene G₄C crystalline network through a combination of non‐covalent interactions. UV irradiation of the crystals transforms the entrapped Me₂1 into a 4,6‐dimethyl‐Dewar‐β‐lactone intermediate, Me₂2 , and rectangular‐bent 1,3‐dimethylcyclobutadiene, Me₂CBD^R , which are sufficiently stable under the confined conditions at 175 K to allow a conventional structure determination by X‐ray diffraction. Further irradiation drives the reaction towards Me₂3&Me₂CBD^S /CO₂ (63.7 %) and Me₂CBD^R (37.3 %) superposed crystalline architectures and the amplification of Me₂CBD^R . The crystallographic models are supported by additional FTIR and Raman experiments in the solid state and by ¹H NMR spectroscopy and ESI mass spectrometry experiments in aqueous solution. Amazingly, the 4,6‐dimethyl‐Dewar‐β‐lactone, Me₂2 , the cyclobutadiene‐carboxyl zwitterion, Me₂3 , and 1,3‐dimethylcyclobutadiene, Me₂CBD , were obtained by ultraviolet irradiation of an aqueous solution of G₄C{Me₂1} . 1,3‐Dimethylcyclobutadiene is stable in water at room temperature for several weeks and even up to 50 °C as demonstrated by ¹H NMR spectroscopy.     

Physio-chemical influence of high electron-phonon coupling induced by 120 MeV Ag9+ SHI irradiation on exfoliated MoS2 - PVA nanocomposite films for achieving remarkable electrical conductivity for potential application in organic electronics

Swift heavy ion (SHI) irradiation technology is known to enhance the optical, electronic, mechanical, and electrical properties in polymer nanocomposites by the virtue of electron-phonon coupling. In the present work, Molybdenum disulphide (MoS₂), a two-dimensional metal dichalcogenide, has been exfoliated via liquid-phase exfoliation using N-methyl-2- pyrrolidone (NMP) as the solvent that yielded nanosheets of around 2–4 layers as depicted by HR-TEM images. MoS₂ - PVA free-standing films were prepared by wet chemical technique i.e. solution casting method and irradiated by focussed high-energy Ag⁹⁺ ion beam at fluence range of 1E10 - 3E11 ions/cm². As a consequence, the structural modification was observed by X-Ray diffraction studies that showed the shift of (002) plane of MoS₂ while Raman studies indicated the decrease of degree of disorderness at fluence 1E10 ions/cm². SHI irradiation has found to induce a two-order increase in the electrical conductivity yielding a 9.7 E-3 S/cm against that of the pristine films at 2.6E-5 S/cm. The enhanced conductivity is attributed to the induced dispersion and annealing of MoS₂ nanosheets in the PVA matrix due to the interaction of 120 MeV Ag⁹⁺ ion beam irradiation as explained by Thermal spike model.     

Crystal Structure of Mercury 7-Amylthio-8-mercaptoquinolinate Hg[C9H5(SC5H11)NS]2 and the Structure of the 7-Amylthio-8-mercaptoquinoline Ligand

Mercury 7-amylthio-8-mercaptoquinolinate Hg[C9H₅(SC5H₁₁)NS]₂ has been synthesized and studied by X-ray diffraction. The crystals are triclinic: a = 8.980(2) Å, b = 9.298(2) Å, c = 18.909(4) Å, α = 93.66(2)°, β = 98.00(2)°, γ = 62.25(2)°, V = 1383.7(5) ų, ρ_calcd = 1.74 g/cm³, Z = 2, space group P1?. The structure is formed by neutral asymmetric complexes in which two 7-amylthio-8-mercaptoquinoline ligands coordinate, in a bidentate fashion (N,S), a mercury atom (Hg-S, 2.363(2) and 2.376(2) Å; Hg-N, 2.436(6) and 2.466(7) Å). The coordination polyhedron of mercury, which is a “swing” (2S+2N), has an SHgS bond angle equal to 173.5(1)°. Some structural features of the ligands in mercury, zinc and copper 7-amylthio-8-mercaptoquinolinates are discussed.     

Determination of very low levels of inorganic and organic mercury in natural waters by cold-vapor atomic absorption spectrometry after preconcentration on a chelating resin

Inorganic and organic mercury at ng l^?1 levels in fresh waters are collected simultaneously on a column of a dithiocarbamate-treated resin and quantitatively eluted with slightly acidic aqueous thiourea solution. Mercury vapor is generated from inorganic mercury by reduction with alkaline SnCl₂ solution, and from inorganic and organic mercury with a CdCl₂SnCl₂ solution, for determination by cold-vapor atomic absorption spectrometry. The range of determination is 0.2–5,000 ppt (ng l^?1) for 20-l water samples.     

Unraveling the Mechanisms of the Excited-State Intermolecular Proton Transfer (ESPT) for a D-π-A Molecular Architecture

Precise revealing the mechanisms of excited-state intermolecular proton transfer (ESPT) and the corresponding geometrical relaxation upon photoexcitation and photoionization remains a formidable challenge. In this work, the compound (E)-4-(((4H-1,2,4-triazol-4-yl)imino)methyl)-2,6-dimethoxyphenol (TIMDP) adopting a D-π-A molecular architecture featuring a significant intramolecular charge transfer (ICT) effect has been designed. With the presence of perchloric acid (35 %), TIMDP can be dissolved through the formation of a HClO₄–H₂O–OH(TIMDP)–N(TIMDP) hydrogen-bonding bridge. At the ground state, the ICT effect is dominant, giving birth to crystals of TIMDP. Upon external stimuli (e.g., UV light irradiation, electro field), the excited state is achieved, which weakens the ICT effect, and significantly promotes the ESPT effect along the hydrogen-bonding bridge, resulting in crystals of [HTIMDP]⁺ ⋅ [H₂O] ⋅ [ClO₄]⁻. As a consequence, the mechanisms of the ESPT can be investigated, which distorted the D-π-A molecular architecture, tuned the emission color with the largest Stokes shift of 242 nm, and finally, high photoluminescence quantum yields (12 %) and long fluorescence lifetimes (8.6 μs) have achieved. These results not only provide new insight into ESPT mechanisms, but also open a new avenue for the design of efficient ESPT emitters.     

Hg2(OH)[BF4], the First Basic Mercurous Tetrafluoroborate

The first basic mercurous tetrafluoroborate, Hg₂(OH)[BF₄], was obtained through a synproportionation reaction of red mercuric oxide, HgO, and elemental mercury in a 35% solution of HBF₄ in water as colourless single crystals. The crystal structure (orthorhombic, Pbca, Z = 8, a = 985.0(1), b = 991.0(1), c = 1141.0(2) pm) contains [(HO)_1/2—Hg—Hg—(OH)_1/2]⁺ zig‐zag chains that are further connected via weak Hg—OH interchain interactions to layers between which the [BF₄]^— are located in an up and down fashion.