Qualitative Analysis of Nitrogen and Sulfur Compounds in Vacuum Gas Oils via Matrix-Assisted Laser Desorption Ionization Time of Flight Mass Spectrometry.

Analysis of the heavy fractions in crude oil has been important in petroleum industries. It is well known that heavy fractions such as vacuum gas oils (VGOs) include heteroatoms, of which sulfur and nitrogen are often characterized in many cases. We conducted research regarding the molecular species analysis of VGOs. Further refine processes using VGOs are becoming important when considering carbon recycling. In this work, we attempted to classify compounds within VGOs provided by Kuwait Institute for Scientific Research. Two VGOs were priorly distillated from Kuwait Export crude and Lower Fars crude. Quantitative analysis was performed mainly using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOFMS). MALDI-TOF-MS has been developed for analyzing high-molecular-weight compounds such as polymer and biopolymers. As matrix selection is one of the most important aspects in MALDI-TOFMS, the careful selection of a matrix was firstly evaluated, followed by analysis using a Kendrick plot with nominal mass series (z*). The objective was to evaluate if this work could provide an effective classification of VGOs compounds. The Kendrick plot is a well-known method for processing mass data. The difference in the Kendrick mass defect (KMD) between CnH2n-14S and CnH2n-20O is only 0.0005 mass units, which makes it difficult in general to distinguish these compounds. However, since the z* value showed effective differences during the classification of these compounds, qualitative analysis could be possible. The analysis using nominal mass series showed the potential to be used as an effective method in analyzing heavy fractions.

Nonlinear Optical and Magnetic Properties of FeII-SCN-HgII Isomers: Centrosymmetric Layers and Chiral Networks.

Research on isomers is highly desirable due to their prospective role in better understanding of physicochemical properties of similar systems and further development of multifunctional molecular materials. Iron(II) and tetra(thiocyanato)mercury(II) ions self-assembled in the presence of 2-acetylpyridine (2-acpy) excess to form two {[Fe(2-acpy)][Hg(µ-SCN)4]}n isomers: two-dimensional (2D) centrosymmetric layers with folded ring structural motifs (1) and three-dimensional (3D) chiral networks with right- or left-handed {···Fe-NCS-Hg-SCN···}∞ helixes (2). New methods of designing and synthesizing functional thiocyanate-bridged materials have been proposed. In addition, the similarity between 1 and 2 allowed for the description of subtle changes in IR and UV-visible spectra. Moreover, 2 shows spontaneous resolution, and it crystallizes in the noncentrosymmetric space group P21, leading to the occurrence of nonlinear optical activity in circular dichroism studies and second harmonic generation (SHG). At room temperature, the SH susceptibility for powder sample 2 reached 6.0 × 10-11 esu. Ab initio calculations indicated the electric polarization vector and the crystallographic twofold screw axis pass through the aromatic ring. Magnetic studies for 1 and 2 revealed high-spin iron(II) with zero-field splitting at low temperatures. Analysis of magnetic data gave |D| = 37.45 cm-1, |E/D| = 5.59 cm-1, and ⟨g⟩ = 2.15 for 1, |D| = 36.78 cm-1, |E/D| = 4.92 cm-1, and ⟨g⟩ = 2.18 for 2, and information about the orientation of magnetic anisotropy vectors for both compounds.

Low-Frequency Sub-Terahertz Absorption in HgII -XCN-FeII (X=S, Se) Coordination Polymers.

Self-assembly FeII complexes of phenazine (Phen), quinoxaline (Qxn), and 4,4'-trimethylenedipyridine (Tmp) with tetrahedral building blocks of [HgII (XCN)4 ]2- (X=S or Se) formed six new high-dimensional frameworks with the general formula of [Fe(L)m ][Hg(XCN)4 ]⋅solvents (L=Phen, m/X=2/S, 1; L=Qxn, m/X=2/S, 2; L=Qxn, m/X=1/S, 3; L=Qxn, m/X=1/Se, 3-Se; L=Tmp, m/X=1/S, 4; and L=Tmp, m/X=1/Se, 4-Se). 1, 3, and 3-Se show an intense sub-terahertz (sub-THz) absorbance of around 0.60 THz due to vibrations of the solvent molecules coordinated to the FeII ions and crystallization organic molecules. In addition, crystals of 1, 4, and 4-Se display low-frequency Raman scattering with exceptionally low values of 0.44, 0.51, and 0.53 THz, respectively. These results indicate that heavy metal FeII -HgII systems are promising platforms to construct sub-THz absorbers.

Synchronous Switching of Dielectric Constant and Photoluminescence in Cyanidonitridorhenate-Based Crystals.

Switching of multiple physical properties by external stimuli in dynamic materials enables applications in, e.g., smart sensors, biomedical tools, as well as data-storage devices. Among stimuli-responsive materials, inorganic-organic molecular hybrids exhibiting thermal order-disorder phase transitions were tested as promising molecular switches of electrical characteristics, including dielectric constant. We aimed at broadening the multifunctional potential of such hybrid materials towards the switching of not only electrical but also other physical properties, e.g., light emission. We report two ionic salts based on luminescent tetracyanidonitridorhenate(V) anions bearing two different diamine ligands, 1,2-diaminoethane (1) and 1,3-diaminopropane (2), both crystallizing with polar N-methyl-dabconium cations. They exhibit an order-disorder phase transition related to the heating-induced turning-on of the rotation of polar cations. This leads to a unique synchronous switching of the dielectric constant as well as metal-complex-centered photoluminescence, as demonstrated by changes in, e.g., emission lifetime. The roles of organic cations, non-trivial Re(V) complexes, and their interaction in achieving the coupled thermal switching of electrical and optical properties are discussed utilizing experimental and theoretical approaches.

Development of Nd (III)-Based Terahertz Absorbers Revealing Temperature Dependent Near-Infrared Luminescence.

Molecular vibrations in the solid-state, detectable in the terahertz (THz) region, are the subject of research to further develop THz technologies. To observe such vibrations in terahertz time-domain spectroscopy (THz-TDS) and low-frequency (LF) Raman spectroscopy, two supramolecular assemblies with the formula [NdIII (phen)3 (NCX)3] 0.3EtOH (X = S, 1-S; Se, 1-Se) were designed and prepared. Both compounds show several THz-TDS and LF-Raman peaks in the sub-THz range, with the lowest frequencies of 0.65 and 0.59 THz for 1-S and 1-Se, and 0.75 and 0.61 THz for 1-S and 1-Se, respectively. The peak redshift was observed due to the substitution of SCN- by SeCN-. Additionally, temperature-dependent TDS-THz studies showed a thermal blueshift phenomenon, as the peak position shifted to 0.68 THz for 1-S and 0.62 THz for 1-Se at 10 K. Based on ab initio calculations, sub-THz vibrations were ascribed to the swaying of the three thiocyanate/selenocyanate. Moreover, both samples exhibited near-infrared (NIR) emission from Nd (III), and very good thermometric properties in the 300-150 K range, comparable to neodymium (III) oxide-based thermometers and higher than previously reported complexes. Moreover, the temperature dependence of fluorescence and THz spectroscopy analysis showed that the reduction in anharmonic thermal vibrations leads to a significant increase in the intensity and a reduction in the width of the emission and LF absorption peaks. These studies provide the basis for developing new routes to adjust the LF vibrational absorption.

Ratiometric and Colorimetric Optical Thermometers Using Emissive Dimeric and Trimeric {[Au(SCN)2 ]- }n Moieties Generated in d-f Heterometallic Assemblies.

Gold complexes can generate excimers ([Au2 ]→[Au2 ]*) and exciplexes ([Au3 ]→[Au3 ]*) with light excitation. Four GdIII and YIII complexes were assembled with dimeric {[Au(SCN)2 ]- }2 and trimeric {[Au(SCN)2 ]- }3 bis(thiocyanato)gold(I) counterions. The vibrational signature associated with the Au⋅⋅⋅Au vibrational mode was probed with ultralow frequency (ULF) Raman spectroscopy as a function of temperature. Emission spectroscopy was used to explore photophysical properties. Two broad features in the high- and low-energy regions were associated with the fluorescence and phosphorescence of the gold entities, respectively. Temperature-dependent luminescence measurements showed that the emission color can be tuned from blue to green via cyan and white. Hence, these complexes can act as colorimetric thermometers. Additionally, a ratiometric thermal sensing ability was incorporated with high sensitivity up to 5 % K-1 in the cryogenic temperature range.

Magnetic Properties and Second Harmonic Generation of Noncentrosymmetric Cyanido-Bridged Ln(III)-W(V) Assemblies.

One-dimensional zigzag cyanido-bridged coordination polymers have been prepared as a result of self-assembly of lanthanide(III) ions with octacyanidotungstate(V) anions in the presence of N,N-dimethylacetamide (dma). All compounds crystallized in noncentrosymmetric space group P21 with a molecular formula of [LnIII(dma)5][WV(CN)8] [Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5), Tm (6), Yb (7), Lu (8), or Y (9)]. Magnetic studies revealed weak antiferromagnetic interactions through LnIII-NC-WV bridges and the formation of ferrimagnetically coupled chains at very low temperatures. Moreover, temperature dependencies of magnetic susceptibilities were fitted using the crystal field parameters for Ln(III) ions, determined by the ab initio calculations, yielding magnetic coupling constants in the range of -1 to -5 cm-1. The wide optical transparency of 1-9 has been determined using solid state absorption spectroscopy. Samples exhibited second harmonic (SH) generation properties with SH susceptibilities ranging from 4.7 × 10-12 to 9.4 × 10-11 esu due to the presence of nonlinear optical susceptibility tensor elements (χijk) χzxx, χzyy, χzzz, χzxy, χyyz, χyzx, χxyz, and χxzx, corresponding to space group P21. The determined values were also compared with the results of theoretical calculations and previous reports, indicating a potential relationship between the type of lanthanide ion and the SH intensity.

Screening of COVID-19 polymerase chain reaction tests using saliva for pregnant women and their partners in Himeji city.

A screening of coronavirus disease 2019 (COVID-19) polymerase chain reaction (PCR) tests using saliva for pregnant women and their partners was performed at all 12 maternity facilities located in Himeji city between May 29 and September 5, 2020. Pregnant women at 37 or more weeks of gestation or who experienced threatened labor and their partners who cared for an infant underwent a saliva PCR test with informed consent. As a result, all of 1475 pregnant women and 1343 partners tested negative for COVID-19 PCR. There were no cases of false positive or false negative PCR tests. This cohort study revealed for the first time that a screening of COVID-19 PCR tests using saliva may be useful to sustain perinatal medical care during the pandemic period in Japan.

Room-Temperature Bistability in a Ni-Fe Chain: Electron Transfer Controlled by Temperature, Pressure, Light, and Humidity.

Bistable and stimuli-responsive molecule-based materials are promising candidates for the development of molecular switches and sensors for future technologies. The CN-bridged {NH4 [Ni(cyclam)][Fe(CN)6 ]⋅5 H2 O}n chain exists in two valence states: NiII -FeIII (1HT ) and NiIII -FeII (1LT ) and shows unique multiresponsivity under ambient conditions to various stimuli, including temperature, pressure, light, and humidity, which generate measurable response in the form of significant changes in magnetic susceptibility and color. The electron-transfer phase transition 1LT ↔1HT shows room-temperature thermal hysteresis, can be induced by irradiation, and shows high sensitivity to small applied pressure, which shifts it to higher temperatures. Additionally, it can be reversibly turned off by dehydration to the {NH4 [NiII (cyclam)][FeIII (CN)6 ]}n (1 d) phase, which features the NiII -FeIII valence state over the whole temperature range, but responds to pressure by yielding NiIII -FeII above 1.06 GPa.

Proton Conductive Luminescent Thermometer Based on Near-Infrared Emissive {YbCo2} Molecular Nanomagnets.

Lanthanide(III)-based coordination complexes have been explored as a source of bifunctional molecular materials combining Single-Molecule Magnet (SMM) behavior with visible-to-near-infrared photoluminescence. In pursuit of more advanced multifunctionality, the next target is to functionalize crystalline solids based on emissive molecular nanomagnets toward high proton conductivity and an efficient luminescent thermometric effect. Here, a unique multifunctional molecule-based material, (H5O2)2(H)[YbIII(hmpa)4][CoIII(CN)6]2·0.2H2O (1, hmpa = hexamethylphosphoramide), composed of molecular {YbCo2}3- anions noncovalently bonded to acidic H5O2+ and H+ ions, is reported. The resulting YbIII complexes present a slow magnetic relaxation below 6 K and room temperature NIR 4f-centered photoluminescence sensitized by [Co(CN)6]3- ions. The microporous framework, built on these emissive magnetic molecules, exhibits a high proton conductivity of the H-hopping mechanism reaching σ of 1.7 × 10-4 S·cm-1 at 97% relative humidity, which classifies 1 as a superionic conductor. Moreover, the emission pattern is strongly temperature-dependent which was utilized in achieving a highly sensitive single-center luminescent thermometer with a relative thermal sensitivity, Sr > 1% K-1 in the 50-175 K range. This work shows an unprecedented combination of magnetic, optical, and electrical functionalities in a single phase working as a proton conductive NIR-emissive thermometer based on Single-Molecule Magnets.

Octacyanidorhenate(V) Ion as an Efficient Linker for Hysteretic Two-Step Iron(II) Spin Crossover Switchable by Temperature, Light, and Pressure.

A two-step hysteretic FeII spin crossover (SCO) effect was achieved in programmed layered Cs{[Fe(3-CNpy)2 ][Re(CN)8 ]}⋅H2 O (1) (3-CNpy=3-cyanopyridine) assembly consisting of cyanido-bridged FeII -ReV square grid sheets bonded by Cs+ ions. The presence of two non-equivalent FeII sites and the conjunction of 2D bimetallic coordination network with non-covalent interlayer interactions involving Cs+ , [ReV (CN)8 ]3- ions, and 3-CNpy ligands, leads to the occurrence of two steps of thermal SCO with strong cooperativity giving a double thermal hysteresis loop. The resulting spin-transition phenomenon could be tuned by an external pressure giving the room-temperature range of SCO, as well as by visible-light irradiation, inducing an efficient recovery of the high-spin FeII state at low temperatures. We prove that octacyanidorhenate(V) ion is an outstanding metalloligand for induction of a cooperative multistep, multiswitchable FeII SCO effect.

Dehydration-Hydration Switching of Single-Molecule Magnet Behavior and Visible Photoluminescence in a Cyanido-Bridged DyIIICoIII Framework.

Microporous magnets compose a class of multifunctional molecule-based materials where desolvation-driven structural transformation leads to the switching of magnetic properties. Herein, we present a special type of microporous magnet where a dehydration-hydration process within a bimetal coordination framework results in the switching of emissive DyIII single-molecule magnets (SMMs). We report a three-dimensional (3-D) cyanido-bridged coordination polymer, {[DyIII(H2O)2][CoIII(CN)6]}·2.2H2O (1), and its dehydrated form of {DyIII[CoIII(CN)6]} (2), which was obtained through a reversible single-crystal-to-single-crystal transformation. Both phases are composed of paramagnetic DyIII centers alternately arranged with diamagnetic hexacyanidocobaltates(III). The hydrated phase contains eight-coordinated [DyIII(µ-NC)6(H2O)2]3- complexes of a square antiprism geometry, while the dehydrated form contains six-coordinated [DyIII(µ-NC)6]3- moieties of a trigonal prism geometry. This change in coordination geometry results in the generation of DyIII single-molecule magnets in 2, whereas slow magnetic relaxation effect is not observed for DyIII sites in 1. The D4d-to-D3h symmetry change of DyIII complexes produces also the shift of photoluminescent color from nearly white to deep yellow thanks to the modulation of emission bands of f-f electronic transitions. A combined approach utilizing dc magnetic data and low-temperature emission spectra confirmed an axial crystal field of trigonal prismatic DyIII complexes in 2, which produces an Orbach type of slow magnetic relaxation. Therefore, we present a unique route to the efficient switching of SMM behavior and photoluminescence of DyIII complexes embedded in a 3-D cyanido-bridged framework.

Photoluminescent Lanthanide(III) Single-Molecule Magnets in Three-Dimensional Polycyanidocuprate(I)-Based Frameworks.

Three-dimensional bimetallic cyanido-bridged frameworks, [LnIII (2,2'-bipyridine N,N'-dioxide)2 (H2 O)][CuI 2 (CN)5 ]⋅5 H2 O (Ln=Dy, 1; Yb, 2), are reported. They exhibit the effect of slow relaxation of magnetization, leading to a magnetic hysteresis loop, and sensitized visible-to-near-infrared photoluminescence. Both physical properties are related to the eight-coordinated lanthanide(III) complexes embedded in the unprecedented coordination skeleton composed of symmetry-breaking polycyanidocuprate linkers. The three-dimensional d-f cyanido-bridged network was shown to serve as an efficient coordination scaffold to achieve emissive lanthanide single-molecule magnets.

Effect of Noble Metals on Luminescence and Single-Molecule Magnet Behavior in the Cyanido-Bridged Ln-Ag and Ln-Au (Ln = Dy, Yb, Er) Complexes.

Self-assembly of lanthanide(III) complexes of 2,2':6',2″-terpyridine (terpy) with dicyanidoargentate(I) and dicyanidoaurate(I) anions in water results in the formation of six isostructural dinuclear systems [LnIII(terpy)(H2O)(NO3)2][MI(CN)2] (LnIII/MI = Dy/Ag, 1; Dy/Au, 2; Yb/Ag, 3; Yb/Au, 4; Er/Ag, 5; Er/Au, 6). They form three-dimensional supramolecular networks based on dinuclear molecules linked by hydrogen bonds, π-π interactions, and argentophilic (Ag···Ag) or aurophilic (Au···Au) interactions. All of the assemblies show complex solid-state strong UV and weak vis-NIR absorption due to overlapping contributions from 2,2':6',2″-terpyridine, dicyanidoargentate(I), dicyanidoaurate(I), and lanthanide(III) ions. Moreover, they exhibit excitation-wavelength-dependent multicolor photoluminescence ranging from bright white to blue via yellow, green, and cyan colors due to variable contributions from the dicyanidometalate and ligand. Assemblies 3-6 show NIR emission originating from YbIII and ErIII metal centers. Furthermore, compounds 1-6 and their magnetically diluted samples are magnetic-field-induced single-molecule magnets with energy barriers of up to 35 K. The effect of noble metal substitution on the magnetic properties of particular lanthanide ions is described. The influence on the thermal anisotropic energy barrier, which relates to the strength of the magnetic anisotropy, depends on the type of lanthanide used. The Ag-to-Au substitution enhances the anisotropy of the prolate YbIII ion and decreases it for the oblate DyIII ion. It also modifies the strength of dipolar interactions affecting the slow magnetic relaxation processes.

In Situ Ligand Transformation for Two-Step Spin Crossover in FeII[MIV(CN)8]4- (M = Mo, Nb) Cyanido-Bridged Frameworks.

We report a unique synthetic route toward the multistep spin crossover (SCO) effect induced by utilizing the partial ligand transformation during the crystallization process, which leads to the incorporation of three different FeII complexes into a single coordination framework. The 3-acetoxypyridine (3-OAcpy) molecules were introduced to the self-assembled FeII-[MIV(CN)8]4- (M = Mo, Nb) system in the aqueous solution which results in the partial hydrolysis of the ligand into 3-hydroxypyridine (3-OHpy). It gives two novel isostructural three-dimensional {FeII2(3-OAcpy)5(3-OHpy)3[MIV(CN)8]}· nH2O (M = Mo, n = 0, FeMo; M = Nb, n = 1, FeNb) coordination frameworks. They exhibit an unprecedented cyanido-bridged skeleton composed of {Fe3M2} n coordination nanotubes bonded by additional Fe complexes. These frameworks contain three types of Fe sites differing in the attached organic ligands, [Fe1(3-OAcpy)4(µ-NC)2], [Fe2(3-OHpy)4(µ-NC)2], and [Fe3(3-OAcpy)3(3-OHpy)(µ-NC)2], which lead to the thermal two-step FeII SCO, as proven by X-ray diffraction, magnetic susceptibility, UV-vis-NIR optical absorption, and 57Fe Mössbauer spectroscopy studies. The first step of SCO, going from room temperature to the 150-170 K range with transition temperatures of 245(5) and 283(5) K for FeMo and FeNb, respectively, is related to Fe1 sites, while the second step, occurring at the 50-140 K range with transition temperatures of 70(5) and 80(5) K for FeMo and FeNb, respectively, is related to Fe2 sites. The Fe3 site with both 3-OAcpy and 3-OHpy ligands does not undergo the SCO at all. The observed two-step SCO phenomenon is explained by the differences in the ligand field strength of the Fe complexes and the role of their alignment in the coordination framework. The simultaneous application of two related pyridine derivatives is the efficient synthetic route for the multistep FeII SCO in the cyanido-bridged framework which is a promising step toward rational design of advanced spin transition molecular switches.

Acid-Responsive Conductive Nanofiber of Tetrabenzoporphyrin Made by Solution Processing.

While cofacial one-dimensional (1-D) π stacking of a planar aromatic molecule is ideal for the construction of conduction systems, such molecules, including tetrabenzoporphyrin (BP), prefer to form edge-to-face stacking through CH-π interactions. We report here that the BP molecules spontaneously form a 1-D cofacial stack in chloroform containing 1% trifluoroacetic acid (TFA) and that a bundle of the formed nanofiber shows acid-responsive 1-D conductivity as high as 1904 S m-1. A small fraction (2.7%) of BP in the fiber exists in a cation radical state, and 1.5 equiv of TFA is located in an intercolumnar void. Dedoping and redoping of TFA with trimethylamine vapor results in 1300-2700-fold decreases and increases, respectively, in the conductivity and also the amount of the radical cation. The conductivity of the fiber also shows a correlation with the pKa of acid dopants.

Dehydration-Triggered Charge Transfer and High Proton Conductivity in (H3O)[NiIII(cyclam)][MII(CN)6] (M = Ru, Os) Cyanide-Bridged Chains.

The coexistence of dehydration-driven charge transfer, magnetic interactions, and high proton conductivity was found in two bimetallic alternating CN-bridged chains {(H3O)[NiIII(cyclam)][MII(CN)6]·5H2O} n (M = Ru (1), Os (2); cyclam = 1,4,8,11-tetraazacyclotetradecane). Dehydration of these materials causes structural transformation and triggers charge transfer between the metal centers: NiIII-NC-MII → NiII-NC-MIII. The CT process, whose extent is tuned by the change of the anionic building block, causes significant increase of magnetic moment, appearance of antiferromagnetic interactions, and noticeable changes in color. The high conductivity values of σ = 1.09 × 10-3 (1) and 1.12 × 10-3 S cm-1 (2) at 295 K and 100% relative humidity allow the classification of the materials as superionic conductors. The proton conduction occurs according to the Grotthuss mechanism as a hopping of protons between H-bonded water molecules due to the presence of the H3O+ ions, which compensate negative charge of the coordination chains.

Fine Tuning of Multicolored Photoluminescence in Crystalline Magnetic Materials Constructed of Trimetallic EuxTb1-x[Co(CN)6] Cyanido-Bridged Chains.

Coordination compounds built of trivalent lanthanide ions have been demonstrated as promising solid-state materials for diverse photoluminescent applications and as attractive magnetic objects with the prospective application in information storage and spintronics. We present a synthetic methodology in which both luminescent and magnetic functionalities are induced within lanthanide-based coordination polymers by the application of hexacyanocobaltate(III) anions and 3-hydroxypyridine (3-OHpy), both coordinated to 4f-metal ions modulating the lanthanide-centered properties. We report a series of trimetallic cyanido-bridged chains {[EuIIIxTbIII1-x(3-OHpy)2(H2O)4][CoIII(CN)6]}·H2O (x = 1, 0.8, 0.5, 0.4, 0.3, 0.2, 0.1, 0; compounds 1, 2, ..., 7, 8). They reveal tunable visible photoluminescence ranging from green, through yellow and orange, to red color depending on the composition of material and the wavelength of UV excitation light. Such multicolored emission is realized by the adjusted ratio between red emissive Eu3+ and green emissive Tb3+ and by the selection of wavelengths of UV light controlling the intensities of Eu- and Tb-based components of visible luminescence. The photoluminescence is enhanced by the energy-transfer (ET) process from [CoIII(CN)6]3- and 3-OHpy to lanthanides, and the efficiencies of ET to Eu and Tb play an important role in the switchable emission. The whole family, 1-8, exhibits temperature-dependent paramagnetism due to the intrinsic property of lanthanide(3+) ions. Tb-containing 2-8 reveal the field-induced slow relaxation of magnetization due to the magnetic anisotropy of Tb3+. Moreover, the compounds built of large amounts of Tb reveal the double relaxation, the faster of a typical TbIII single-ion origin, and the slower originating from the magnetic dipole-magnetic dipole interactions between neighboring TbIII centers. Compound 2, which can be considered as a magnetically diluted sample, exhibits almost single relaxation process with the thermal energy barrier ΔE/kB of 35.8(6) K and τ0 = 1.1(2) × 10-8 s at Hdc = 1500 Oe, indicating a single-molecule magnet behavior.

Bis(aminoaryl) Carbon-Bridged Oligo(phenylenevinylene)s Expand the Limits of Electronic Couplings.

Carbon-bridged bis(aminoaryl) oligo(para-phenylenevinylene)s have been prepared and their optical, electrochemical, and structural properties analyzed. Their radical cations are class III and class II mixed-valence systems, depending on the molecular size, and they show electronic couplings which are among the largest for the self-exchange reaction of purely organic molecules. In their dication states, the antiferromagnetic coupling is progressively tuned with size from quinoidal closed-shell to open-shell biradicals. The data prove that the electronic coupling in the radical cations and the singlet-triplet gap in the dications show similar small attenuation factors, thus allowing charge/spin transfer over rather large distances.

Tuning of Charge Transfer Assisted Phase Transition and Slow Magnetic Relaxation Functionalities in {Fe(9-x)Co(x)[W(CN)8]6} (x = 0-9) Molecular Solid Solution.

Precisely controlled stoichiometric mixtures of Co(2+) and Fe(2+) metal ions were combined with the [W(V)(CN)8](3-) metalloligand in a methanolic solution to produce a series of trimetallic cyanido-bridged {Fe(9-x)Co(x)[W(CN)8]6(MeOH)24}·12MeOH (x = 0, 1, ..., 8, 9; compounds 0, 1, ..., 8, 9) clusters. All the compounds, 0-9, are isostructural, and consist of pentadecanuclear clusters of a six-capped body-centered cube topology, capped by methanol molecules which are coordinated to 3d metal centers. Thus, they can be considered as a unique type of a cluster-based molecular solid solution in which different Co/Fe metal ratios can be introduced while preserving the coordination skeleton and the overall molecular architecture. Depending on the Co/Fe ratio, 0-9 exhibit an unprecedented tuning of magnetic functionalities which relate to charge transfer assisted phase transition effects and slow magnetic relaxation effects. The iron rich 0-5 phases exhibit thermally induced reversible structural phase transitions in the 180-220 K range with the critical temperatures being linearly dependent on the value of x. The phase transition in 0 is accompanied by (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) charge transfer (CT) and the additional minor contribution of a Fe-based spin crossover (SCO) effect. The Co-containing 1-5 phases reveal two simultaneous electron transfer processes which explore (HS)Fe(II) W(V) ↔ (HS)Fe(III) W(IV) CT and the more complex (HS)Co(II) W(V) ↔ (LS)Co(III) W(IV) charge transfer induced spin transition (CTIST). Detailed structural, spectroscopic, and magnetic studies help explain the specific role of both types of CN(-)-bridged moieties: the Fe-NC-W linkages activate the molecular network toward a phase transition, while the subsequent Co-W CTIST enhances structural changes and enlarges thermal hysteresis of the magnetic susceptibility. On the second side of the 0-9 series, the vanishing phase transition in the cobalt rich 6-9 phases results in the high-spin ground state, and in the occurrence of a slow magnetic relaxation process at low temperatures. The energy barrier of the magnetic relaxation gradually increases with the increasing value of x, reaching up to ΔE/kB = 22.3(3) K for compound 9.