A Solid‐State Electrochemiluminescence Sensor for Label‐Free Analysis of Leukemia Cells

A novel electrochemiluminescence (ECL) method for label‐free detection of cancer cells was proposed for the first time by capturing negatively charged Jurkat cells onto Ru(bpy′)${{{2+\hfill \atop 3\hfill}}}$ ‐immobilized indium tin oxide (ITO) electrode via electrostatic interaction. The ECL sensor exhibited excellent sensitivity, good stability and a linear response to Jurkat cells in the concentration range from 1×10³ to 2×10⁵ cells/mL, with a detection limit of 730 cells/mL. Furthermore, the method was successfully applied in the study of cell growth and cell apoptosis, which was supported by fluorescent images analysis. The proposed protocol is simple, rapid, inexpensive and universally targetable for tumors, offering a novel platform for the development of an ECL biosensor for cell detection.     

Polysulfide Chemistry in Sodium–Sulfur Batteries and Related Systems— A Computational Study by G3X(MP2) and PCM Calculations

The sodium–sulfur (NAS) battery is a candidate for energy storage and load leveling in power systems, by using the reversible reduction of elemental sulfur by sodium metal to give a liquid mixture of polysulfides (Na₂S_n) at approximately 320 °C. We investigated a large number of reactions possibly occurring in such sodium polysulfide melts by using density functional calculations at the G3X(MP2)/B3LYP/6‐31+G(2df,p) level of theory including polarizable continuum model (PCM) corrections for two polarizable phases, to obtain geometric and, for the first time, thermodynamic data for the liquid sodium–sulfur system. Novel reaction sequences for the electrochemical reduction of elemental sulfur are proposed on the basis of their Gibbs reaction energies. We suggest that the primary reduction product of S₈ is the radical anion ${{\rm S}{{{{\bullet}}- \hfill \atop 8\hfill}}}$ , which decomposes at the operating temperature of NAS batteries exergonically to the radicals ${{\rm S}{{{{\bullet}}- \hfill \atop 2\hfill}}}$ and ${{\rm S}{{{{\bullet}}- \hfill \atop 3\hfill}}}$ together with the neutral species S₆ and S₅, respectively. In addition, ${{\rm S}{{{{\bullet}}- \hfill \atop 8\hfill}}}$ is predicted to disproportionate exergonically to S₈ and ${{\rm S}{{2- \hfill \atop 8\hfill}}}$ followed by the dissociation of the latter into two ${{\rm S}{{{{\bullet}}- \hfill \atop 4\hfill}}}$ radical ions. By recombination reactions of these radicals various polysulfide dianions can in principle be formed. However, polysulfide dianions larger than ${{\rm S}{{2- \hfill \atop 4\hfill}}}$ are thermally unstable at 320 °C and smaller dianions as well as radical monoanions dominate in Na₂S_n (n=2–5) melts instead. The reverse reactions are predicted to take place when the NAS battery is charged. We show that ion pairs of the types ${{\rm NaS}{{{{\bullet}}\hfill \atop 2\hfill}}}$ , ${{\rm NaS}{{- \hfill \atop n\hfill}}}$ , and Na₂S_n can be expected at least for n=2 and 3 in NAS batteries, but are unlikely in aqueous sodium polysulfide except at high concentrations. The structures of such radicals and anions with up to nine sulfur atoms are reported, because they are predicted to play a key role in the electrochemical reduction process. A large number of isomerization, disproportionation, and sulfurization reactions of polysulfide mono‐ and dianions have been investigated in the gas phase and in a polarizable continuum, and numerous reaction enthalpies as well as Gibbs energies are reported.     

Unprecedented Electron‐Poor Octahedral Ta6 Clusters in a Solid‐State Compound: Synthesis,Characterisations and Theoretical Investigations of Cs2BaTa6Br15O3

The crystal structure of Cs₂BaTa₆Br₁₅O₃ has been elucidated by using synchrotron X‐ray powder diffraction and absorption experiments. It is built from edge‐bridged octahedral [(Ta₆${{\rm Br}{{{\rm i}\hfill \atop 9\hfill}}}$ ${{\rm O}{{{\rm i}\hfill \atop 3\hfill}}}$ )${{\rm Br}{{{\rm a}\hfill \atop 6\hfill}}}$ ]^4? cluster units with a singular poor metallic electron (ME) count equal to thirteen. This leads to a paramagnetic behaviour related to one unpaired electron. The arrangement of the Ta₆ clusters is similar to that of Cs₂LaTa₆Br₁₅O₃ exhibiting 14‐MEs per [(Ta₆${{\rm Br}{{{\rm i}\hfill \atop 9\hfill}}}$ ${{\rm O}{{{\rm i}\hfill \atop 3\hfill}}}$ )${{\rm Br}{{{\rm a}\hfill \atop 6\hfill}}}$ ]^5? motif. The poorer electron‐count cluster presents longer metal–metal distances as foreseen according to the electronic structure of edge‐bridged hexanuclear cluster. Density functional theory (DFT) calculations on molecular models were used to rationalise the structural properties of 13‐ and 14‐ME clusters. Periodic DFT calculations demonstrate that the electronic structure of these solid‐state compounds is related to those of the discrete octahedral units. Oxygen–barium interactions seem to prevent the geometry of the octahedral cluster to strongly distort, allowing stabilisation of this unprecedented electron‐poor Ta₆ cluster in the solid state.     

Guanidinium Alkynesulfonates with Single‐Layer Stacking Motif: Interlayer Hydrogen Bonding Between Sulfonate Anions Changes the Orientation of the Organosulfonate R Group from “Alternate Side” to “Same Side”

Hydrolyses of HC?CSO₃SiMe₃ ( 1 ) and CH₃C?CSO₃SiMe₃ ( 2 ) lead to the formation of acetylenic sulfonic acids HC?CSO₃H?2.33 H₂O ( 3 ) and CH₃C?CSO₃H?1.88 H₂O ( 4 ). These acids were reacted with guanidinium carbonate to yield [⁺C(NH₂)₃][HC?CSO₃^?] ( 5 ) and [⁺C(NH₂)₃][CH₃C?CSO₃^?] ( 6 ). Compounds 1 – 6 were characterized by spectroscopic methods, and the X‐ray crystal structures of the guanidinium salts were determined. The X‐ray results of 5 show that the guanidinium cations and organosulfonate anions associate into 1D ribbons through ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) dimer interactions, whereas association of these ions in 6 is achieved through ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) and ${{\rm R}{{1\hfill \atop 2\hfill}}}$ (6) interactions. The ribbons in 5 associate into 2D sheets through ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) dimer interactions and ${{\rm R}{{3\hfill \atop 6\hfill}}}$ (12) rings, whereas those in 6 are connected through ${{\rm R}{{1\hfill \atop 2\hfill}}}$ (6) and ${{\rm R}{{2\hfill \atop 2\hfill}}}$ (8) dimer interactions and ${{\rm R}{{4\hfill \atop 6\hfill}}}$ (14) rings. Compound 6 exhibits a single‐layer stacking motif similar to that found in guanidinium alkane‐ and arenesulfonates, that is, the alkynyl groups alternate orientation from one ribbon to the next. The stacking motif in 5 is also single‐layer, but due to interlayer hydrogen bonding between sulfonate anions, the alkynyl groups of each sheet all point to the same side of the sheet.     

Calixarene‐Based Surfactants: Conformational‐Dependent Solvation Shells for the Alkyl Chains

Thermodynamic parameters obtained from studying the micellization of amphiphilic p‐sulfonatocalix[n]arenes were correlated with the alkyl chain length and with the number of monomeric units (n) in the calix[n]arene structure. The micellization Gibbs free energy (Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ ) becomes more negative upon increasing the alkyl chain length of the p‐sulfonatocalix[4]arene. This is in agreement with the trend generally observed for other surfactants. However, the Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ value for transferring one CH₂ group from the bulk aqueous medium to the micelle [Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ (CH₂)] is lower than the value generally observed for single‐chain surfactants, suggesting the existence of intramolecular interactions between the alkyl chains of the free unimers. On the other hand, the critical micelle concentration (cmc; per alkyl chain unit) increased with the increasing number of monomeric units. These results are explained on the basis of the conformation adopted by the calixarene in the bulk solution. The calix[4]arene derivatives are preorganized into the cone conformation, which is favorable for the formation of globular aggregates. The calix[6]arene and calix[8]arene derivatives do not adopt cone conformations. Changing these conformations to the more favorable cone conformer in the aggregates implies an energetic cost that contributes to making Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ less efficient. In the case of the calix[6]arene derivative this energetic cost is enthalpic, whereas in the case of the octamer it is both enthalpic and entropic. Both the Δ${G{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ (CH₂) value and the change in heat capacity (ΔC${{\rm p}{{{\rm o}\hfill \atop {\rm M}\hfill}}}$ ) seem to indicate that for the cone calix[4]arene derivatives all alkyl chains are solvated by the same hydration shell, whereas in the case of the highly flexible calix[8]arene derivative each alkyl chain is individually hydrated.     

Crystal Structures and Emitting Properties of Trifluoromethylaminoquinoline Derivatives: Thermal Single‐Crystal‐to‐Single‐Crystal Transformation of Polymorphic Crystals That Emit Different Colors

2,4‐Trifluoromethylquinoline (TFMAQ) derivatives that have amine ( 1 ), methylamine ( 2 ), phenylamine ( 3 ), and dimethylamine ( 4 ) substituents at the 7‐position of the quinoline ring were prepared and crystallized. Six crystals including the crystal polymorphs of 2 (crystal GB and YG) and 3 (crystal B and G) were obtained and characterized by X‐ray crystallography. In solution, TFMAQ derivatives emitted relatively strong fluorescence (${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$ =418–469 nm and Φ_f(s)=0.23–0.60) depending on the solvent polarity. From Lippert–Mataga plots, Δμ values in the range of 7.8–14 D were obtained. In the crystalline state, TFMAQ derivatives emitted at longer wavelengths (${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$ =464–530 nm) with lower intensity (Φ_f(c)=0.01–0.28) than those in n‐hexane solution. The polymorphous crystals of 2 and 3 emitted different colors: 2 , ${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$ =470 and 530 nm with Φ_f(c)=0.04 and approximately 0.01 for crystal GB and YG, respectively; and 3 , ${\lambda {{{\rm f}\hfill \atop {\rm max}\hfill}}}$ =464 and 506 nm with Φ_f(c)=0.28 and approximately 0.28 for crystal B and G, respectively. In both crystal polymorphs of 2 and 3 , crystals GB and G showed emission color changes by heating/melting/cooling cycles that were representative. By following the color changes in heating at the temperature below the melting point with X‐ray diffraction measurements and X‐ray crystallography, the single‐crystal‐to‐single‐crystal transformations from crystal GB to YG for 2 and from crystal B to G for 3 were revealed.     

Enhanced Electrogenerated Chemiluminescence of Tris(2,2′‐bipyridyl) Ruthenium(II)/tripropylamine in the Presence of Pyridine and Its Analogues

In the present work, we conducted an investigation on the electrochemical and ECL behavior of Ru(bpy) /TPrA system in the presence of pyridine and its analogues on platinum and gold electrode. Results showed that pyridine and its analogues enhanced Ru(bpy) /TPrA ECL signal and exhibited different enhancement effects on different electrodes. On platinum electrode, the maximum enhancement factor of about 5 was obtained. On gold electrode, a low‐oxidation‐potential (LOP) ECL signal occurred and increased.     

A Copper–Formate Framework Showing a Simple to Helical Antiferroelectric Transition with Prominent Dielectric Anomalies and Anisotropic Thermal Expansion,and Antiferromagnetism

We present here the compound [NH₄][Cu(HCOO)₃], a new member of the [NH₄][M(HCOO)₃] family. The Jahn–Teller Cu²⁺ ion leads to a distorted 4⁹?6⁶ chiral Cu–formate framework. In the low‐temperature (LT) orthorhombic phase, the Cu²⁺ is in an elongated octahedron, and the ${{\rm NH}{{+\hfill \atop 4\hfill}}}$ ions in the framework channel are off the channel axis. From 94 to 350 K the ${{\rm NH}{{+\hfill \atop 4\hfill}}}$ ion gradually approaches the channel axis and the related modulation of the framework and the hydrogen‐bond system occurs. The LT phase is simple antiferroelectric (AFE). The material becomes hexagonal above 355 K. In the high‐temperature (HT) phase, the Cu²⁺ octahedron is compressed, and the ${{\rm NH}{{+\hfill \atop 4\hfill}}}$ ions are arranged helically along the channel axis. Therefore, the phase transition is one from LT simple AFE to HT helical AFE. The temperature‐dependent structure evolution is accompanied by significant thermal and dielectric anomalies and anisotropic thermal expansion, due to the different status of the ${{\rm NH}{{+\hfill \atop 4\hfill}}}$ ions and the framework modulations, and the structure–property relationship was established based on the extensive variable‐temperature single‐crystal structures. The material showed long range ordering of antiferromagnetism (AFM), with low dimensional character and a Néel temperature of 2.9 K. Therefore, within the material AFE and AFM orderings coexist in the low‐temperature region.     

A First‐Principles Study on the Interaction between Alkyl Radicals and Graphene

The interaction between alkyl radicals and graphene was studied by means of dispersion‐corrected density functional theory. The results indicate that isolated alkyl radicals are not likely to be attached onto perfect graphene. It was found that the covalent binding energies are low, and because of the large entropic contribution, Δ${G{{{\ominus}\hfill \atop 298\hfill}}}$ is positive for methyl, ethyl, isopropyl, and tert‐butyl radicals. Although the alkylation may proceed by moderate heating, the desorption barriers are low. For the removal of the methyl and tert‐butyl radicals covalently bonded to graphene, 15.3 and 2.4 kcal mol^?1 are needed, respectively. When alkyl radicals are agglomerated, the binding energies are increased. For the addition in the ortho position and on opposite sides of the sheet, the graphene–CH₃ binding energy is increased by 20 kcal mol^?1, whereas for the para addition on the same side of the sheet, the increment is 9.4 kcal mol^?1. In both cases, the agglomeration turns the Δ${G{{{\ominus}\hfill \atop 298\hfill}}}$ <0. For the ethyl radical, the ortho addition on opposite sides of the sheet has a negative Δ${G{{{\ominus}\hfill \atop 298\hfill}}}$ , whereas for isopropyl and tert‐butyl radicals the reactions are endergonic. The attachment of the four alkyl radicals under consideration onto the zigzag edges is exergonic. The noncovalent adsorption energies computed for ethyl, isopropyl, and tert‐butyl radicals are significantly larger than the graphene–alkyl‐radical covalent binding energies. Thus, physisorption is favored over chemisorption. As for the Δ${G{{{\ominus}\hfill \atop 298\hfill}}}$ for the adsorption of isolated alkyl radicals, only the tert‐butyl radical is likely to be exergonic. For the phenalenyl radical we were not able to locate a local minimum for the chemisorbed structure since it moves to the physisorbed structure. An important conclusion of this work is that the consideration of entropic effects is essential to investigate the interaction between graphene and free radicals.     

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

We report herein some outstanding examples of atropisomerism and tautomerism in five (meso‐)strapped porphyrins. Porphyrins S0 – S4 have been synthesised, characterised and studied in detail by spectroscopic and spectrometric techniques, and their isomeric purity verified by HPLC analysis. In particular, they exhibit perfectly well‐defined NMR spectra that display distinct patterns depending on their average symmetry at room temperature: C_2v, D_2d, C_2h, C_2v, and D_2h for S0 – S4 , respectively. NH tautomerism was evidenced by variable‐low‐temperature ¹H NMR experiments in [D₂]dichloromethane performed on S0 (Δ${G{{{\ne}\hfill \atop {\rm 298K}\hfill}}}$ =48±1 kJ mol^?1) and S1 (Δ${G{{{\ne}\hfill \atop {\rm 298K}\hfill}}}$ =55±3 kJ mol^?1), which has led to an understanding of the average spectra observed for the five porphyrins at room temperature. On the other hand, S2 and S3 are stable atropisomers at room temperature, easily separated and characterised, as a result of restricted rotation of their strapped bridges due to their high rotational barrier energies. Upon heating to 82 °C, they slowly equilibrate to a thermodynamic ratio of 64:36 in favour of the more stable S2 isomer. This atropisomerisation process was evidenced by ¹H NMR spectroscopy and monitored by HPLC, from which high rotational energy barriers of 115.2 (Δ${G{{{\ne}\hfill \atop {\rm S2}\rightarrow {\rm S3}\hfill}}}$ ) and 116.9 kJ mol^?1 (Δ${G{{{\ne}\hfill \atop {\rm S2}\rightarrow {\rm S3}\hfill}}}$ ) were deduced.     

Tuning the Photocatalytic Activity of CdS Nanocrystals through Intermolecular Interactions in Ionic‐Liquid Solvent Systems

Synthetic solvent systems for the fine‐tuned preparation of CdS nanocrystallites, active in visible‐light photocatalytic hydrogen production, were studied. To control crystallite size and spectral properties, the CdS crystals were synthesised by using different solvent systems, containing a series of tetrabutylammonium amino carboxylate ionic liquids as the crystal‐growth control agents. Six samples of CdS, all with similar physical and spectral properties, exhibited greatly varying photocatalytic activity, with the most active sample outperforming the least active one by almost 60 %. To rationalise this effect, the intermolecular interactions of the synthesis solvent system with the growing CdS nanocrystallites were characterised by using the Reichart betaine dye and the ${E{{{\rm N}\hfill \atop {\rm T}\hfill}}}$ polarity scale. A correlation was observed between the ${E{{{\rm N}\hfill \atop {\rm T}\hfill}}}$ values of the solvent system and the photocatalytic activity of the CdS nanocrystallite, suggesting that the hydrogen‐bond‐donating ability and/or dipolarity/polarisability interactions of the solvent system led to the preferential formation of active surfaces/surface sites on the CdS crystals.     

Ultrafast Deactivation Mechanism of the Excited Singlet in the Light‐Induced Spin Crossover of [Fe(2,2′‐bipyridine)3]2+

The mechanism of the light‐induced spin crossover of the [Fe(bpy)₃]²⁺ complex (bpy=2,2′‐bipyridine) has been studied by combining accurate electronic‐structure calculations and time‐dependent approaches to calculate intersystem‐crossing rates. We investigate how the initially excited metal‐to‐ligand charge transfer (MLCT) singlet state deactivates to the final metastable high‐spin state. Although ultrafast X‐ray free‐electron spectroscopy has established that the total timescale of this process is on the order of a few tenths of a picosecond, the details of the mechanisms still remain unclear. We determine all the intermediate electronic states along the pathway from low spin to high spin and give estimates for the deactivation times of the different stages. The calculations result in a total deactivation time on the same order of magnitude as the experimentally determined rate and indicate that the complex can reach the final high‐spin state by means of different deactivation channels. The optically populated excited singlet state rapidly decays to a triplet state with an Fe d⁶(${{\rm t}{{5\hfill \atop {\rm 2g}\hfill}}}$ ${{\rm e}{{1\hfill \atop {\rm g}\hfill}}}$ ) configuration either directly or by means of a triplet MLCT state. This triplet ligand‐field state could in principle decay directly to the final quintet state, but a much faster channel is provided by internal conversion to a lower‐lying triplet state and subsequent intersystem crossing to the high‐spin state. The deactivation rate to the low‐spin ground state is much smaller, which is in line with the large quantum yield reported for the process.     

Rubidium Polyhydrides Under Pressure: Emergence of the Linear H3− Species

The structures of compressed rubidium polyhydrides, RbH_n with n>1, and their evolution under pressure are studied using density functional theory calculations. These phases, which start to stabilize at only P=2 GPa, consist of Rb⁺ cations and one or more of the following species: H^? anions, H₂ molecules, and ${{\rm H}{{- \hfill \atop 3\hfill}}}$ molecules. The latter motif, the simplest example of a three‐center four‐electron bond, is found in the most stable structures, RbH₅ and RbH₃, which metallize above 200 GPa. At the highest pressures studied, our evolutionary searches find an RbH₆ phase which contains polymeric (${{\rm H}{{- \hfill \atop 3\hfill}}}$ )_∞ chains that show signs of one‐dimensional liquid‐like behavior.     

Photochemistry of RuII 4,4′‐Bi‐1,2,3‐triazolyl (btz) Complexes: Crystallographic Characterization of the Photoreactive Ligand‐Loss Intermediate trans‐[Ru(bpy)(κ2‐btz)(κ1‐btz)(NCMe)]2+

We report the unprecedented observation and unequivocal crystallographic characterization of the meta‐stable ligand loss intermediate solvento complex trans‐[Ru(bpy)(κ²‐btz)(κ¹‐btz)(NCMe)]²⁺ ( 1 a ) that contains a monodentate chelate ligand. This and analogous complexes can be observed during the photolysis reactions of a family of complexes of the form [Ru($\widehat{NN}$ )(btz)₂]²⁺ ( 1 a – d : btz=1,1′‐dibenzyl‐4,4′‐bi‐1,2,3‐triazolyl; $\widehat{NN}$ =a) 2,2′‐bipyridyl (bpy), b) 4,4′‐dimethyl‐2,2′‐bipyridyl (dmbpy), c) 4,4′‐dimethoxy‐2,2′‐bipyridyl (dmeobpy), d) 1,10‐phenanthroline (phen)). In acetonitrile solutions, 1 a – d eventually convert to the bis‐solvento complexes trans‐[Ru($\widehat{NN}$ )(btz)(NCMe)₂]²⁺ ( 3 a – d ) along with one equivalent of free btz, in a process in which the remaining coordinated bidentate ligands undergo a new rearrangement such that they become coplanar. X‐ray crystal structure of 3 a and 3 d confirmed the co‐planar arrangement of the $\widehat{NN}$ and btz ligands and the trans coordination of two solvent molecules. These conversions proceed via the observed intermediate complexes 2 a – d , which are formed quantitatively from 1 a – d in a matter of minutes and to which they slowly revert back on being left to stand in the dark over several days. The remarkably long lifetime of the intermediate complexes (>12 h at 40 °C) allowed the isolation of 2 a in the solid state, and the complex to be crystallographically characterized. Similarly to the structures adopted by complexes 3 a and d , the bpy and κ²‐btz ligands in 2 a coordinate in a square‐planar fashion with the second monodentate btz ligand coordinated trans to an acetonitrile ligand.     

Fabrication and Properties of Redox Ion Doped Few Monolayer Thick Polyelectrolyte Film for Electrochemical Biosensors at High Sensitivity and Specificity

Redox ions are deposited on a polyelectrolyte‐coated gold electrode by an electric field to fabricate an ion‐selective thin film electrode. The Fe(CN)${{{4- \hfill \atop 6\hfill}}}$ ions are deposited on a few monolayer‐coated polyelectrolyte gold electrode by a slow periodic potential cycle. The deposition process and electrode properties are quantitatively and simultaneously monitored by cyclic voltammetry and a novel technique, using a Scanning Electrometer for Electrical Double‐layers (SEED). No redox properties are obtained without the electric‐field‐deposition. Owing to the redox mediation and net charge due to the redox ion, the electrode is ion‐selective. We demonstrate the principle to detect 1 µM of dopamine in a mixture with 1 mM of ascorbic acid.     

A Bis(pyridine N‐oxide) Analogue of DOTA: Relaxometric Properties of the GdIII Complex and Efficient Sensitization of Visible and NIR‐Emitting Lanthanide(III) Cations Including PrIII and HoIII

We report the synthesis of a cyclen‐based ligand (4,10‐bis[(1‐oxidopyridin‐2‐yl)methyl]‐1,4,7,10‐tetraazacyclododecane‐1,7‐diacetic acid= L1 ) containing two acetate and two 2‐methylpyridine N‐oxide arms anchored on the nitrogen atoms of the cyclen platform, which has been designed for stable complexation of lanthanide(III) ions in aqueous solution. Relaxometric studies suggest that the thermodynamic stability and kinetic inertness of the Gd^III complex may be sufficient for biological applications. A detailed structural study of the complexes by ¹H NMR spectroscopy and DFT calculations indicates that they adopt an anti‐Δ(λλλλ) conformation in aqueous solution, that is, an anti‐square antiprismatic (anti‐SAP) isomeric form, as demonstrated by analysis of the ¹H NMR paramagnetic shifts induced by Yb^III. The water‐exchange rate of the Gd^III complex is ${k{{298\hfill \atop {\rm ex}\hfill}}}$ =6.7×10⁶ s^?1, about a quarter of that for the mono‐oxidopyridine analogue, but still about 50 % higher than the ${k{{298\hfill \atop {\rm ex}\hfill}}}$ of GdDOTA (DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid). The 2‐methylpyridine N‐oxide chromophores can be used to sensitize a wide range of Ln^III ions emitting in both the visible (Eu^III and Tb^III) and NIR (Pr^III, Nd^III, Ho^III, Yb^III) spectral regions. The emission quantum yield determined for the Yb^III complex (${Q{{{\rm L}\hfill \atop {\rm Yb}\hfill}}}$ =7.3(1)×10^?3) is among the highest ever reported for complexes of this metal ion in aqueous solution. The sensitization ability of the ligand, together with the spectroscopic and relaxometric properties of its complexes, constitute a useful step forward on the way to efficient dual probes for optical imaging (OI) and MRI.     

New Nuclear‐Spin‐Induced Cotton–Mouton Effect in Fluids at High DC Magnetic Field

Based on Buckingham and Pople’s theory of magnetic double refraction, a theoretical expression is derived for a new Cotton–Mouton effect ${\phi _{{\rm{C}} - {\rm{M}}}^{(IB)} }$ in liquid induced by the crossed effect between the high dc magnetic field B₀ and the nuclear magnetic moment ${m_z^{(I)} }$ . It contains temperature‐independent and ‐dependent parts. The latter is proportional to the product between anisotropy of polarizability and the nuclear magnetic shielding tensor. For this new effect ${\phi _{{\rm{C}} - {\rm{M}}}^{(IB)} }$ , its order in magnitude for a molecule with large polarizability anisotropy is estimated to be comparable to the nuclear‐spin‐induced optical Faraday rotation (NSOFR). In the multipass approach, ${\phi _{{\rm{C}} - {\rm{M}}}^{(IB)} }$ can be eliminated by time‐reversal symmetry arguments, but NSOFR is enhanced.     

Electric and magnetic dipole shielding constants for the ground state of the relativistic hydrogen‐like atom: Application of the Sturmian expansion of the generalized Dirac‐Coulomb Green function

The Sturmian expansion of the generalized Dirac‐Coulomb Green function (Szmytkowski, J Phys B, 1997, 30, 825; erratum 1997, 30, 2747) is exploited to derive closed‐form expressions for electric $(\sigma_{E})$ and magnetic $(\sigma_{M})$ dipole shielding constants for the ground state of the relativistic hydrogen‐like atom with a point‐like and spinless nucleus of charge Ze. It is found that $\sigma_{E}=Z^{-1}$ (as it should be) and where $\gamma_{1}=\sqrt{1-(Z\alpha)^{2}}$ (α is the fine‐structure constant). This expression for $\sigma_{M}$ agrees with earlier findings of several other authors, obtained with the use of other analytical techniques, and is elementary compared to an alternative one presented recently by Cheng et al. (J Chem Phys 2009, 130, 144102), which involves an infinite series of ratios of the Euler's gamma functions. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

One‐Pot Hydrothermal Synthesis of Heterostructured ZnO/ZnS Nanorod Arrays with High Ethanol‐Sensing Properties

ZnO/ZnS heterostructured nanorod arrays with uniform diameter and length were synthesized from zinc substrates in a one‐pot procedure by using a simple hydrothermal method. Structural characterization by HRTEM indicated that the heterostructured nanorods were composed of parallel segments of wurtzite‐type ZnO and zinc‐blende ZnS, with a distinct interface along the axial direction, which revealed the epitaxial relationship, ZnO (10$\bar 1$ 0) and ZnS ($\bar 1$ 1$\bar 1$ ). The as‐prepared ZnO/ZnS nanorods showed only two green emissions at around 523 nm and 576 nm. We also found that the nanorods exhibited high sensitivity to ethanol at relatively low temperatures, owing to their smaller size and structure.