Combination of metastable and ground-state mercury atoms into ungerade dimer states

The time evolution of the 2537 Å sensitised luminescence of mercury vapour has been examined at 304 K. With a trace of N₂ to generate Hg(6³P_o) and an excess of Ar to chaperon dimer formation, full time profiles of the ultraviolet and green bands have been recorded. The ultraviolet emission is of much shorter duration than the green with these gas mixtures. The reservoir of the ultraviolet band is the O^?_u state of the mercury dimer which correlates with Hg(6³P_o), Hg(6¹S_o) and is generated in the combination of metastable and ground-state mercury atoms. The Hg₂ O^?_u is efficiently relaxed to the O^±_g firstexcited states of the dimer in collision with Hg atoms, but rather inefficiently in collisions with Ar atoms. The rate coefficient for formation of excited trimers in the reaction Hg₂ O^±_g+ Hg(6¹S_o) + N₂ → Hg^*₃ + N₂ has been recorded as 1.95(±0.1) × 10^?30 cm⁶ molecule^?2s^?1 at 304 K.     

A novel and efficient excitation- and ionization-scheme for laser resonance ionization of mercury

A novel, efficient scheme for mercury atomic resonance ionization is proposed and experimentally studied with wavelengths λ₁=254 nm, λ₂=313 nm and λ₃=626 nm. The cross-sections of mercury photoionization from different excited states were estimated using a new imaging method of resonance ionization signal measurement. Almost 100% efficiency of Hg resonance ionization was achieved using the first harmonic of a dye laser at 626 nm to ionize mercury atoms excited into the 6³D₂ state. The photoionization cross-section from this state was found to be 1.5×10⁻¹⁸ cm². Suppression of the ionization signal by coherent effects (electromagnetically-induced transparency) and the efficiency of resonance ionization were also studied.     

Manganese mercury thio­cyanate (MMTC) glycol mono­methyl ether

In the title complex, [MnHg(NCS)₄(C₃H₈O₂)]_n, each Hg atom is tetrahedrally coordinated with four S atoms of the SCN^? ions, and each Mn atom is octahedrally coordinated with four N atoms of the SCN^? ions, one hydroxyl O atom and one ethereal O atom of the glycol mono­methyl ether mol­ecule. Each pair of Hg and Mn atoms is bridged by one SCN^? ion. A 24‐membered Mn₃Hg₃(SCN)₆ ring is formed as the strucrural unit, with the six metal atoms in a chair‐form hexagonal arrangement. The units are condensed and linked three‐dimensionally in the crystal resulting in a diamond‐like structure.     

A violet emission from optically excited mercury vapour. Kinetics of the formation and decay of excited dimers and trimers

A new electronic systems has been observed from excited Hg vapour, which is assigned to collisionally induced emission from the Hg₂ O^±_g first excited states of the dimer: Hg₂O^±_g + M → 2Hg(6 ¹S₀) + M + hv(γ_max 3950 A). For M = N₂, the rate coefficient is 5.3(±0.7) × 10^?19 cm³ molecule^?1 at 298 K. From time resolved measurements of the luminescence in the afterglow following pulsed excitation, the decay rate of the green emission, in an excess of N₂, is shown to be a linear function of [Hg][N₂]. It is concluded that the reaction which controls the decay of the excitation is formation of an excited trimer in a termolecular reaction; the trimer is the carrier of the green emission: Hg₂ O^±_g + Hg(6 ¹S₀ + Hg(6¹S₀ + N₂ → Hg₃³Π_u + N₂. The rate coefficient is 1.10(±0.07) × 10^?30 cm⁶ molecule^?2 s^?1 at 298 K.     

Quenching cross sections for the deactivation of metastable mercury 6 (3P0)

By monitoring the relative concentrations of mercury ³P₀ atoms using absorption photometry, absolute rate constants have been measured for the excimer-forming reaction Hg (³P₀) + Hg + N₂ → Hg₂* + N₂ and for the quenching of Hg (³P₀) atoms by ethane, propane, deuterated propanes, and nitrous oxide.     

Homoligand and mixed-ligand complexes of mercury(II) with aspartic acid and iminodiacetic acid and its derivatives

The formation of homoligand mercury(II) complexes with aspartic acid (H₂Asp) and aspartate-chelant mixed-ligand mercury(II) complexes with iminodiacetic acid (H₂Ida, IDA), 2-hydroxyethyliminodiacetic acid (H₂Heida, HEIDA), and nitrilotriacetic acid (H₃Nta, NTA) in an aqueous perchlorate medium was studied by spectrophotometry and pH-potentiometric titration. The following complexes were identified: [Hg(OH)Asp]^?, [HgAsp₂]^2?, [Hg(Asp)Ida]^2?, [Hg(Asp)Heida]^2?, and [Hg(Asp)Nta]^3?. The logarithms of their stability constants are, respectively, 11.74 ± 0.12, 20.18 ± 0.17, 20.11 ± 0.10, 19.82 ± 0.09, 19.48 ± 0.11, and 20.58 ± 0.07 (μ = 0.1 (NaClO₄), t = (20 ± 2)°C). The hydrogen and hydroxyl competition regions were located in the systems, and relationships between the molar yields of complex species and the reactant concentrations were established. The protonation and dissociation constants of aspartic acid were derived from pH-potentiometric titrations. Experimental data were analyzed using mathematical models allowing one to judge the existence of various complex species in the solution and to identify the species that are sufficient to reproduce the observed data.     

Crystal structure and vibrational spectrum of copper mercury ortho-thiophosphate CuHgPS4

The compound CuHgPS₄ crystallizes in the orthorhombic system, space group Pna2₁ (No. 33), Z = 4, with lattice parameters a = 12.660(3), b = 7.3498(7), c = 6.0943(4) Å, and δ_calc = 4.96 g/cm³. The title compound is stable in air and moisture and behaves as a semiconductor. The crystal structure consists of discrete tetrahedral PS₄^3- anions joined together by Cu⁺ and Hg²⁺ cations. The arrangement of the sulfur atoms is approximately hexagonal close-packed in which P, Cu, and Hg occupy tetrahedral sites. The PS₄, HgS₄, and CuS₄ tetrahedra are slightly distorted with mean distances d(P-S) = 2.055, d(Hg-S) = 2.524, and d(Cu S) = 2.320 Å, and 8% of the Hg atoms were found to be disordered, occupying interstitial tetrahedral sites. The title compound is isotypic to AgZnPS₄ and can be considered to be a defect structure of Enargite (Cu₃AsS₄), which is a substitution derivative of the Wurtzite (ZnS) structure. The CuHgPS₄ vibrational spectrum has been recorded. The internal modes experimentally observed are in accord with the factor group prediction. A tentative assignment of the vibrational frequencies is proposed.     

Indirect ultraviolet determination of cyanide with mercury complexes

Cyanide ion can be determined in the range of 0.50 to 10 parts per million by the decrease in ultraviolet absorption of the mercury complexes HgBr₄^2?, HgCl₄^2?, HgI₄^2?, Hg(SCN)₄^2?, and Hg(SO₃)₂^2?. The decrease in absorbance is linear with cyanide concentration. Reaction of cyanide with the complexes is rapid in pH 6.86 and 9.01 buffers and in water. Solutions of the complexes are reasonably stable.     

Study of excited fragment emission from the electron impact dissociation of volatile mercury(II) halides

Emission resulting, from collisions of 5–200 eV electrons with gaseous H_gX₂, and CH₃H_gX (X = Cl, Br. I) was characterized in the 3800–5600 A region. HgX BX emission dominates and absolute cross section as a function of electron energy were determined. The formation of electronically excited Hg atoms, and the trend of the cross sections with the nature of the halogen atom are discussed in terms of a simple charge transfer model.     

Crystal chemistry of mercury(I) and mercury(I, II) minerals

The crystal structures of 16 mercury(I)- and mercury(I, II)-containing minerals having (Hg-Hg)²⁺ groups are considered. The Hg-Hg and Hg-X bond lengths and the HgHgX angles (X = Cl, Br, I, O, S) are analyzed. A comparative crystal chemical analysis of the environment of Hg atoms is carried out. The Hg-Hg and Hg-X distances vary within 2.43-2.60 and 1.93-2.43 å, respectively; the angles defining the deviation of the X-Hg-Hg-X groups from linearity are from 146 to 177?. In most cases, the coordination environment of the mercury atoms involves the metal atom of the (Hg-Hg)²⁺ dumbbell and the X atom, but in several compounds the coordination number of the mercury atoms increases due to the additional atoms lying 2.5–3.5 å away. In terlinguaite and kuznetsovite, the Hg₃ triangle is rather unusual; in the latter mineral, the Hg-Hg bonds are lengthened to 2.64-2.70 å. The review covers structural data up to May 1997.     

Synthesis and crystal structure of (dibenzo-18-crown-6)bis(thiocyanato-S)mercury(II)

A new host-guest complex (dibenzo-18-crown-6)bis(thiocyanato-S)mercury(II), [Hg(SCN)₂(DB18C6], was synthesized and studied by X-ray diffraction method. The crystal structure (space group P2₁/n, a = 19.372, b = 8.199, c = 31.799 Å, β = 103.58°, Z = 8) was solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.092 for 6392 independent reflections; CAD-4 autodiffractometer, λMoK _α. In two independent similar complex molecules, the Hg²⁺ cation lies in the cavity of the DB18C6 crown ligand and is coordinated by all the six O atoms and is covalently bonded to two S atoms of the SCN^? ligands lying on the opposite sides of the mean plane of the six O atoms of the DB18C6 ligand. The coordination polyhedron of two independent Hg atoms is a distorted hexagonal bipyramid. Both independent DB18C6 ligands have the “butterfly” conformation with the approximate C _2v symmetry.     

Crystallochemistry of mercury chalcogenides. IV. Crystalline structure of two polymorphous modifications of the mercury sulfochalcogenide Hg3S2Br1.5Cl0.5

Two modifications of a new mercury sulfohalide of Hg₃S₂Br_2−x Cl_x (x = 0.5) composition have been grown from the gas phase and explored by X-ray structural analysis. The compounds were obtained at an attempt to synthesize an analogue of the rare mineral arzakite Hg₃S₂(Br, Cl)₂ (Br > Cl). The refinement of the crystalline structures of monoclinic (I) and cubic (II) phases (I: a = 17.824(4) Å, b = 9.238(2) Å, c = 10.269(2) Å, β = 115.69(1)°, V = 1523.8(5) ų, space group C2/m, Z = 8, R = 0.0513; II: a = 18.248(2) Å, V = 6076.4(12) ų, space group Pm3ˉn, Z = 32, R = 0.038) has shown that they are polymorphous modifications of the compound of Hg₃S₂Br_1.5Cl_0.5 formula. The monoclinic modification I is isostractural to the synthetic compound α-Hg₃S₂Br₂. Modification II is isostructural to synthetic β-Hg₃S₂Cl₂. In both structures, each atom S has in its surrounding three atoms of Hg forming umbrella-type groups SHg₃ with spaces Hg—S 2.366–2.430 Å and angles HgSHg 95.66–97.60°. SHg₃-fragments are bound by Hg-apices with the formation of isolated cubic groups [Hg₁₂S₈]. Like that in other structures of mercury chalcohalides, the main role in structure-forming of the investigated compounds is played by atoms of halogens creating a cubic sublattice in which radicals Hg—S are arranged. Original Russian Text Copyright ? 2006 by N. V. Pervukhina, S. A. Magarill, D. Yu. Naumov, S. V. Borisov, V. I. Vasil’yev, and B. G. Nenashev __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 47, No. 2, pp. 318–323, March–April, 2006.     

Crystal structure determination of complexes of monomethylammonium chloride and mercury(II) chloride: CH3NH3HgCl3, (CH3NH3)2HgCl4, and CH3NH3Hg2Cl5

The crystal structures have been determined of CH₃NH₃HgCl₃, (CH₃NH₃)₂HgCl₄, and CH₃NH₃Hg₂Cl₅. In (CH₃NH₃)₂HgCl₄ the Hg^II atom is tetrahedrally coordinated by four Cl atoms with Hg? Cl bond lengths of 2.464 to 2.478 Å. In the other two compounds the Hg^II atom is involved in two short covalent Hg? Cl bonds, forming a pseudo HgCl₂ molecule and two much longer bridging Hg? Cl bonds. The methylammonium groups are connected by hydrogen bonds to the chlorine atoms. The nature of the hydrogen bonding scheme probably causes disorder of the methylammonium groups.     

Dichloro­[(6R,7S,8S,14S)‐(–)‐sparteine‐κ2N,N′]mercury(II)

In the title compound, [HgCl₂(C₁₅H₂₆N₂)], the chiral alkaloid (6R,7S,8S,14S)‐(−)‐l ‐sparteine acts as a bident­ate ligand, with two Cl⁻ ligands occupying the remaining coordination sites, producing a distorted tetra­hedron. The N—Hg—N plane is twisted by 81.1 (2)° from the Cl—Hg—Cl plane. The mid‐point of the N⋯N line does not lie exactly on the Cl—Hg—Cl plane but is tilted towards one of the N atoms by 0.346 Å. Similarly, the mid‐point of the Cl⋯Cl line is tilted toward one of the Cl atoms by 0.163 Å. The packing structure shows that the complex is stabilized by two inter­atomic Cl⋯H contacts involving both Cl atoms and the methyl­ene or methine H atoms of the (−)‐sparteine ligand.     

Crossed-beám chemiluminescence. II. Kinetics and mechanisms for reactions of group IIA Metals in ground and metastable states with fluorine

Visible chemiluminescence technique under crossed-beam conditions has been applied to the study of the reactions of the group IIA metal atoms Mg, Ca, Sr and Ba in their ground state (¹S₀) or in an excited metastable state (³P_i, ³D_i or ¹D₂) with F₂. The monofluoride emission bands are the most prominent features in the chemiluminescence spectrum. Using higher fluorine densities radiation is observed from excited alkaline earth difluorides, which are shown to principally originate from secondary reactions. Formations of MF* are determined to be first order with respect to both the metal atom and the fluorine molecule. Total cross sections for removal of ground state metal atoms from the beam by F₂ are 115 ± 15Ų for Ca, 125 ± 15Ų for Sr, and 160 ± 15Ų for Ba, which is consistent with an electron jump model. Chemiluminescence cross sections are reported for the reactions involving electronically excited reactants M*. Photon yields of 12 ± 3% for Mg*, 18 ± 5% for Ca*, 20 ± 5% for Sr*, and 15 ± 8% for Ba* reacting with F₂ are measured. These high photon yields are remarkable when compared with absolute photon yields for the ground state reactions which indicate that less than 2% of the products are MF* molecules. It was possible to obtain vibrational state distributions for some of the excited monofluorides which are found to be populated in a non-thermal manner. This strongly suggests that the dynamics of the reactions are governed by a direct mechanism. From the crossed-beam chemiluminescence spectra the dissociation energies of the ground state monofluorides are estimated. In addition, improved spectroscopic constants, dissociation energies and dissociation products of some of the excited electronic states of MF are given.     

Ultraviolet Photodissociation Dynamics of m-Bromofluorobenzene at around 240 nm?

The photodissociation dynamics of m-bromofluorobenzene has been experimentally investigated at around 240 nm using the DC-slice velocity map imaging technique. The kinetic energy release spectra and the recoiling angular distributions of fragmented Br(²P_3/2) and Br(²P_1/2) atoms from photodissociation of m-bromofluorobenzene have been measured at different photolysis wavelengths around 240 nm. The experimental results indicate that two dissociation pathways via (pre-)dissociation of the two low-lying ¹ππ^* excited states dominate the production process of the ground state Br(²P_3/2) atoms. Because of the weak spin-orbit coupling effect among the low-lying triplet and singlet states, the spin-orbit excited Br(²P_1/2) atoms are mainly produced via singlet-triplet state coupling in the dissociation step. The similarity between the present results and that recently reported for o-bromofluorobenzene indicates that the substitution position of the fluorine atom does not significantly affect the UV photodissociation dynamics of bromofluorobenzenes.     

Triplet splitting of the 1p state of mercury atoms in inert gas matrices

The effect of O₂ and N₂ impurities on the spectrum of Hg atoms in solid krypton matrices at 20°K has been investigated. The relative intensity of the components of Hg ¹P⁰₁ are shown to depend strongly on the amount of O₂ or N₂ in the matrix. Under certain conditions, the long wavelength triplet component can be completely eliminated. It is shown that the triplet arises from the superposition of spectra of atoms trapped at three distinct trapping sites.     

Photodissociation of 2-Bromobutane by Ion-velocity Map ImagingTechnique

The photodissociation dynamics of 2-bromobutane has been investigated at 233.62 and 233.95 nm by ion-velocity map imaging technique coupled with resonance-enhanced mul-tiphoton ionization. The speed and angular distribution of Br and Br* fragments were determined from the map images. The two Gaussian components, shown in the speed dis-tributions of Br and Br* atoms, are suggested to attribute to the two independent reaction paths of photodissociation for 2-bromobutane at 233.62 and 233.95 nm. The high-energy component is related to the prompt dissociation along the C-Br stretching mode, and the low-energy component to the dissociation from the repulsive mode with bending and C-Br stretching combination. The contributions of the excited ³Q₀, ³Q₁, and ¹Q₁ states to the products (Br and Br*) were discussed. Relative quantum yield of 0.924 for Br(²P_3/2) at about 234 nm in the photodissociation of 2-bromobutane is derived.     

Formation of mercury clusters during pulsed radiolysis of aqueous Hg 2 2+ solutions

Pulsed radiolysis, EPR, and optical spectroscopy were used to investigate the radiation-induced reduction of Hg ₂ ²⁺ ions in aqueous solutions. It was shown that the Hg ₂ ⁺ ions that form as a result of the reduction reaction react rapidly with Hg ₂ ²⁺ with formation of Hg ₄ ³⁺ . Constants of formation and disappearance of these ions were determined. The process of disappearance of this species results in the formation of more complex clusters containing six or more mercury atoms. Further complication of the clusters affords colloidal metal particles.Institute of Physical Chemistry, Russian Academy of Sciences, Moscow 117915. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 9–12, January, 1992.     

Homo- and heteroleptic mercury(II) complexes with monoamino complexones in aqueous solution

Reactions of mercury(II) with iminodiacetic (H₂Ida), 2-hydroxyethyliminodiacetic (H₂Heida), and nitrilotriacetic acids (H₃Nta) were studied by spectrophotometry and pH potentiometry. The resulting complexes included [HgIda], [Hg(OH)Ida]^?, [HgIda₂]^2?, [HgHeida], [Hg(OH)Heida]^?, [Hg(Heida)₂]^2?, [HgNta]^?, [HgNta₂]^4?, [Hg(Ida)Heida]^2?, [Hg(Ida)Nta]^3?, and [Hg(Heida)Nta]^3?. The logarithms of their stability constants calculated for I = 0.1 (NaClO₄) and T = 20 ± 2°C were 11.14 ± 0.07, 20.33 ± 0.08, 19.40 ± 0.10, 11.42 ± 0.04, 19.68 ± 0.11, 18.48 ± 0.09, 13.42 ± 0.05, 20.80 ± 0.08, 19.05 ± 0.06, 20.64 ± 0.11, and 20.53 ± 0.16, respectively. The experimental data were analyzed in terms of the mathematical models that predict the existence of a wide spectrum of complex species in solution and allow one to consider only those species that are sufficient for accurate reproduction of the observed pattern.