UV continuum emission and diagnostics of hydrogen-containing non-equilibrium plasmas

For the first time the emission of the radiative dissociation continuum of the hydrogen molecule ($a^{3}\Sigma_{g}^{+} \to b^{3}\Sigma_{u}^{+}$ electronic transition) is proposed to be used as a source of information for the spectroscopic diagnostics of non-equilibrium plasmas. The detailed analysis of excitation-deactivation kinetics, rate constants of various collisional and radiative transitions and fitting procedures made it possible to develop two new methods of diagnostics of: (1) the ground $X^{1}\Sigma_{g}^{+}$ state vibrational temperature $T_{\text{vib}}$ from the relative intensity distribution, and (2) the rate of electron impact dissociation (d[\mbox{H_{2}}]/dt)_{\text{diss}} from the absolute intensity of the continuum. A known method of determination of $T_{\text{vib}}$ from relative intensities of Fulcher-$\alpha$ bands was seriously corrected and simplified due to the revision of $d \to a$ transition probabilities and cross sections of $d \gets X$ electron impact excitation. General considerations are illustrated with examples of experiments in pure hydrogen capillary-arc and H$_{2}$+Ar microwave discharges.Comment: REVTeX, 25 pages + 12 figures + 9 tables. Phys. Rev. E, eprint replaced because of resubmission to journal after referee's 2nd repor

Distribution and Demography of Antarctic Krill and Salps in the Atlantic Sector of the Southern Ocean during Austral Summer 2021–2022

The study aimed to investigate krill (Euphausia superba) and salp (Salpa thompsoni) populations in the Atlantic sector of the Southern Ocean in January and February 2022. Samples were obtained to measure the abundance, biomass and distribution patterns of krill and salp. Sex differences and feeding habits of the Antarctic krill were determined. The dependence of the physiological state of the studied aquatic organisms on changes in environmental parameters was analyzed. Current data on the association of the dynamics of hydrometeorological parameters and processes with the distribution of chlorophyll a, krill, and salp were obtained. It was established that, at numerous stations, the biomass of salps prevailed over krill. The result indicates the replacement of the Antarctic krill populations by gelatinous zooplankton. The obtained results allow assessment of the biological resource potential in the studied region based on the analysis of the samples collected

Toward Luminescence Vapochromism of Tetranuclear Au^I–Cu^I Clusters

A family of triphosphine gold–copper clusters bearing aliphatic and hydroxyaliphatic alkynyl ligands of general formula [HC­(PPh₂)₃Au₃Cu­(C₂R)₃]⁺ (R = cyclohexyl (<b>1</b>), cyclopentyl (<b>2</b>), Bu^t (<b>3</b>), cyclohexanolyl (<b>4</b>), cyclopentanolyl (<b>5</b>), 2,6-dimethylheptanolyl (<b>6</b>), 2-methylbutanolyl (<b>7</b>), diphenylmethanolyl (<b>8</b>)) was synthesized via a self-assembly protocol, which involves treatment of the (AuC₂R)_<i>n</i> acetylides with the (PPh₂)₃CH ligand in the presence of Cu⁺ ions and NEt₃. Addition of Cl^– or Br^– anions to complex <b>8</b> results in coordination of the halides to the copper atoms to give neutral HC­(PPh₂)₃Au₃CuHal­(C₂COHPh₂)₃ derivatives (Hal = Cl (<b>9</b>), Br (<b>10</b>)). The title compounds were characterized by NMR and ESI-MS spectroscopy, and the structures of <b>1</b>, <b>4</b>, <b>7</b>, and <b>8</b> were determined by single-crystal X-ray diffraction analysis. The photophysical behavior of all of the complexes has been studied to reveal moderate to weak phosphorescence in solution and intense emission in the solid state with a maximum quantum yield of 80%. Exposure of the solvent-free X-ray amorphous samples <b>8</b>–<b>10</b> (R = diphenylmethanolyl) to vapors of the polar solvents (methanol, THF, acetone) switches luminescence with a visible hypsochromic shift of emission of 50–70 nm. The vapochromism observed is tentatively ascribed to the formation of a structurally ordered phase upon absorption of organic molecules by the amorphous solids

Solid-State and Solution Metallophilic Aggregation of a Cationic [Pt(NCN)L]⁺ Cyclometalated Complex

The noncovalent intermolecular interactions (π–π stacking, metallophilic bonding) of the cyclometalated complexes [Pt­(NCN)­L]⁺X^– (NCN = dipyridylbenzene, L = pyridine (<b>1</b>), acetonitrile (<b>2</b>)) are determined by the steric properties of the ancillary ligands L in the solid state and in solution, while the nature of the counterion X^– (X^– = PF₆^–, ClO₄^–, CF₃SO₃^–) affects the molecular arrangement of <b>2</b>·X in the crystal medium. According to the variable-temperature X-ray diffraction measurements, the extensive Pt···Pt interactions and π-stacking in <b>2</b>·X are significantly temperature-dependent. The variable concentration ¹H and diffusion coefficients NMR measurements reveal that <b>2</b>·X exists in the monomeric form in dilute solutions at 298 K, while upon increase in concentration [Pt­(NCN)­(NCMe)]⁺ cations undergo the formation of the ground-state oligomeric aggregates with an average aggregation number of ∼3. The photoluminescent characteristics of <b>1</b> and <b>2</b>·X are largely determined by the intermolecular aggregation. For the discrete molecules the emission properties are assigned to metal perturbed IL charge transfer mixed with some MLCT contribution. In the case of oligomers <b>2</b>·X the luminescence is significantly red-shifted with respect to <b>1</b> and originates mainly from the ³MMLCT excited states. The emission energies depend on the structural arrangement in the crystal and on the complex concentration in solution, variation of which allows for the modulation of the emission color from greenish to deep red. In the solid state the lability of the ligands L leads to vapor-induced reversible transformation <b>1</b> ↔ <b>2</b> that is accompanied by the molecular reorganization and, consequently, dramatic change of the photophysical properties. Time-dependent density functional theory calculations adequately support the models proposed for the rationalization of the experimental observations

Sky-Blue Luminescent Au^I–Ag^I Alkynyl-Phosphine Clusters

Treatment of the (AuC₂R)_<i>n</i> acetylides with phosphine ligand 1,4-bis­(diphenylphosphino)­butane (PbuP) and Ag⁺ ions results in self-assembly of the heterobimetallic clusters of three structural types depending on the nature of the alkynyl group. The hexadecanuclear complex [Au₁₂Ag₄(C₂R)₁₂(PbuP)₆]⁴⁺ (<b>1</b>) is formed for R = Ph, and the octanuclear species [Au₆Ag₂(C₂R)₆(PbuP)₃]²⁺ adopting two structural arrangements in the solid state were found for the aliphatic alkynes (R = Bu^t (<b>2</b>), 2-propanolyl (<b>3</b>), 1-cyclohexanolyl (<b>4</b>), diphenylmethanolyl (<b>5</b>), 2-borneolyl (<b>6</b>)). The structures of the compounds <b>1</b>–<b>4</b> and <b>6</b> were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of <b>1</b>–<b>3</b> in solution. In particular, complexes <b>2</b> and <b>3</b> undergo reversible transformation, which involves slow interconversion of two isomeric forms. The luminescence behavior of the titled clusters has been studied. All the compounds exhibit efficient sky-blue room-temperature phosphorescence both in solution and in the solid state with maximum quantum yield of 76%. The theoretical DFT calculations of the electronic structures demonstrated the difference in photophysical properties of the compounds depending on their structural topology

Sky-Blue Luminescent Au^I–Ag^I Alkynyl-Phosphine Clusters

Treatment of the (AuC₂R)_<i>n</i> acetylides with phosphine ligand 1,4-bis­(diphenylphosphino)­butane (PbuP) and Ag⁺ ions results in self-assembly of the heterobimetallic clusters of three structural types depending on the nature of the alkynyl group. The hexadecanuclear complex [Au₁₂Ag₄(C₂R)₁₂(PbuP)₆]⁴⁺ (<b>1</b>) is formed for R = Ph, and the octanuclear species [Au₆Ag₂(C₂R)₆(PbuP)₃]²⁺ adopting two structural arrangements in the solid state were found for the aliphatic alkynes (R = Bu^t (<b>2</b>), 2-propanolyl (<b>3</b>), 1-cyclohexanolyl (<b>4</b>), diphenylmethanolyl (<b>5</b>), 2-borneolyl (<b>6</b>)). The structures of the compounds <b>1</b>–<b>4</b> and <b>6</b> were determined by single crystal X-ray diffraction analysis. The NMR spectroscopic studies revealed complicated dynamic behavior of <b>1</b>–<b>3</b> in solution. In particular, complexes <b>2</b> and <b>3</b> undergo reversible transformation, which involves slow interconversion of two isomeric forms. The luminescence behavior of the titled clusters has been studied. All the compounds exhibit efficient sky-blue room-temperature phosphorescence both in solution and in the solid state with maximum quantum yield of 76%. The theoretical DFT calculations of the electronic structures demonstrated the difference in photophysical properties of the compounds depending on their structural topology

Toward Luminescence Vapochromism of Tetranuclear Au^I–Cu^I Clusters

A family of triphosphine gold–copper clusters bearing aliphatic and hydroxyaliphatic alkynyl ligands of general formula [HC­(PPh₂)₃Au₃Cu­(C₂R)₃]⁺ (R = cyclohexyl (<b>1</b>), cyclopentyl (<b>2</b>), Bu^t (<b>3</b>), cyclohexanolyl (<b>4</b>), cyclopentanolyl (<b>5</b>), 2,6-dimethylheptanolyl (<b>6</b>), 2-methylbutanolyl (<b>7</b>), diphenylmethanolyl (<b>8</b>)) was synthesized via a self-assembly protocol, which involves treatment of the (AuC₂R)_<i>n</i> acetylides with the (PPh₂)₃CH ligand in the presence of Cu⁺ ions and NEt₃. Addition of Cl^– or Br^– anions to complex <b>8</b> results in coordination of the halides to the copper atoms to give neutral HC­(PPh₂)₃Au₃CuHal­(C₂COHPh₂)₃ derivatives (Hal = Cl (<b>9</b>), Br (<b>10</b>)). The title compounds were characterized by NMR and ESI-MS spectroscopy, and the structures of <b>1</b>, <b>4</b>, <b>7</b>, and <b>8</b> were determined by single-crystal X-ray diffraction analysis. The photophysical behavior of all of the complexes has been studied to reveal moderate to weak phosphorescence in solution and intense emission in the solid state with a maximum quantum yield of 80%. Exposure of the solvent-free X-ray amorphous samples <b>8</b>–<b>10</b> (R = diphenylmethanolyl) to vapors of the polar solvents (methanol, THF, acetone) switches luminescence with a visible hypsochromic shift of emission of 50–70 nm. The vapochromism observed is tentatively ascribed to the formation of a structurally ordered phase upon absorption of organic molecules by the amorphous solids

Supramolecular Au^I–Cu^I Complexes as New Luminescent Labels for Covalent Bioconjugation

Two new supramolecular organometallic complexes, namely, [Au₆Cu₂(C₂C₆H₄<b>CHO</b>)₆(PPh₂C₆H₄PPh₂)₃]­(PF₆)₂ and [Au₆Cu₂(C₂C₆H₄<b>NCS</b>)₆(PPh₂C₆H₄PPh₂)₃]­(PF₆)₂, with highly reactive aldehyde and isothiocyanate groups have been synthesized and characterized using X-ray crystallography, ESI mass spectrometry, and NMR spectroscopy. The compounds obtained demonstrated bright emission in solution with the excited-state lifetime in microsecond domain both under single- and two-photon excitation. The luminescent complexes were found to be suitable for bioconjugation in aqueous media. In particular, they are able to form the covalent conjugates with proteins of different molecular size (soybean trypsin inhibitor, human serum albumin, rabbit anti-HSA antibodies). The conjugates demonstrated a high level of the phosphorescent emission from the covalently bound label, excellent solubility, and high stability in physiological media. The highest quantum yield, storage stability, and luminance were detected for bioconjugates formed by covalent attachment of the aldehyde-bearing supramolecular Au^I–Cu^I complex. The measured biological activity of one of the labeled model proteins clearly showed that introduced label did not prevent the biorecognition and specific protein–protein complex formation that was extremely important for the application of the conjugates in biomolecular detection and imaging

Coordination to Imidazole Ring Switches on Phosphorescence of Platinum Cyclometalated Complexes: The Route to Selective Labeling of Peptides and Proteins via Histidine Residues

In this study, we have shown that substitution of chloride ligand for imidazole (Im) ring in the cyclometalated platinum complex Pt­(phpy)­(PPh₃)Cl (<b>1</b>; phpy, 2-phenylpyridine; PPh₃, triphenylphosphine), which is nonemissive in solution, switches on phosphorescence of the resulting compound. Crystallographic and nuclear magnetic resonance (NMR) spectroscopic studies of the substitution product showed that the luminescence ignition is a result of Im coordination to give the [Pt­(phpy)­(Im)­(PPh₃)]Cl complex. The other imidazole-containing biomolecules, such as histidine and histidine-containing peptides and proteins, also trigger luminescence of the substitution products. The complex <b>1</b> proved to be highly selective toward the imidazole ring coordination that allows site-specific labeling of peptides and proteins with <b>1</b> using the route, which is orthogonal to the common bioconjugation schemes via lysine, aspartic and glutamic acids, or cysteine and does not require any preliminary modification of a biomolecule. The utility of this approach was demonstrated on (i) site-specific modification of the ubiquitin, a small protein that contains only one His residue in its sequence, and (ii) preparation of nonaggregated HSA-based Pt phosphorescent probe. The latter particles easily internalize into the live HeLa cells and display a high potential for live-cell phosphorescence lifetime imaging (PLIM) as well as for advanced correlation PLIM and FLIM experiments