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A series of asymmetric, homoleptic Fe(II) compounds based on the facially-binding tridentate ligand N-methyl-1,1-di(pyridin-2-yl)Cn-amine (LCn) (Cn = butyl, hexyl, octyl, decyl, dodecyl, tetradecyl and hexadecyl alkyl chains) with formula [FeII(LCn)2](X)2·solvate, where n = 4, 14 and X = BF4 (1C4 and 1C14) or n = 6, 8, 10, 12, 16 and X = CF3SO3 (1C6–1C12 and 1C16), are reported. Complexes 1C6 to 1C16 pack in crystalline bilayers in the solid state, forming hydrophobic and hydrophilic regions between adjacent layers of complexes. The combination of short Fe–N bond distances (∼2.00 Å) and SQUID magnetic susceptibility measurements show that the complexes are in the low-spin state across all measured temperature ranges. Differential scanning calorimetry confirmed phase transitions occur in compounds 1C6, 1C12, 1C14 and 1C16 upon heating from room temperature. The lack of any spin transitions and thermal stability conferred by thermogravimetric analysis over this temperature range suggest that these transitions are crystallographic in nature. 1H NMR studies show that the low-spin Fe(II) centres undergo partial conversion to paramagnetic species in solution. UV-vis spectroscopy in a range of common organic solvents show that the central Fe ions remain in the +2 oxidation state, suggesting that the increase in magnetic susceptibility in solution is likely due to partial spin-crossover, or due to speciation, in which a proportion of the compounds are high-spin Fe(II) complexes. [ABSTRACT FROM AUTHOR]

Boron-β-diketonates are classical emissive materials that have been utilized in various fields, however, boron monothio-β-thioketonates, where one oxygen atom is exchanged for a sulphur atom, have not been explored in detail. To gain a better understanding of this class of materials, we synthesised various aryl substituted monothio-β-diketonate boron complexes with two different aryl substitutions on the boron center and studied their structural, optical and electrochemical properties. Single crystal X-ray analysis revealed that there is considerable deviation in B–O and B–S bond lengths for bis(pentafluorophenyl)boron complexes against diphenyl boron complexes. The bis(pentafluorophenyl)boron complexes have a relatively high absorption coefficient over diphenyl boron complexes. More importantly, a striking difference was observed for the emission behaviour of these compounds. The bis(pentafluorophenyl)boron complexes exhibit weak emission in the solution as well as in the solid state, whereas diphenyl boron complexes do not show any emission in either solution or the solid state. Further, the electrochemical study reveals that diphenyl boron complexes show a reduction potential that is more negative compared to the bis(pentafluorophenyl)boron complexes. The high absorption coefficient of the compounds pointed towards the possibility of high first order hyperpolarizability upon optical excitation, which motivated us to ascertain the nonlinear optical coefficients in the near infrared range, towards applicability of such compounds in optical limiting and switching. The open aperture Z-scan measurements at ultrashort time scales elucidated a few critical features of such compounds towards optical limiting applications. [ABSTRACT FROM AUTHOR]

Spin-crossover complexes, valued for their bistability, are extensively studied due to their numerous potential applications. A primary challenge in this molecular class is to identify effective methods to adjust the spin-transition temperature, which frequently falls outside the desired temperature range. This typically necessitates intricate chemical design and synthesis or the use of stimuli such as light or pressure, each introducing its own set of challenges for integrating these molecules into end-user applications. In this work, we aim to address this challenge using an oriented external electric field (OEEF) as one stimulus to modulate the spin-transition temperatures. For this purpose, we have employed both periodic and non-periodic calculations on three well-characterised Fe(II) SCO complexes, namely [Fe(phen)2(NCS)2] (1, phen = 1,10-phenanthroline), [Fe(bt)2(NCS)2] (2, bt = 2,2'-bi-2-thiazoline) and [Fe(py)2phen(NCS)2] (3, py = pyridine) possessing a similar structural motif of {FeN4N'2}. To begin with, DFT calculations employing the TPSSh functional were performed on complexes 1 to 3, and the estimated low-spin (LS) and high-spin (HS) gaps are 24.6, 15.3 and 15.4 kJ mol-1, and these are in the range expected for Fe(II) SCO complexes. In the next step, an OEEF was applied in the molecule along the pseudo-C2 axis that bisects two coordinated -NCS groups. Application of an OEEF was found to increase the Fe-ligand bond length and found to affect the spin-transition at the particular applied OEEF. While the HS state of 1 becomes the ground state at an applied field of 0.514 V Å-1, the LS state lies at a higher energy of 1.3 kJ mol-1. Similarly, complexes 2 and 3 also show the HS ground state at an applied field of 0.514 V Å-1, where the LS state stays at higher energies of 6.13 and 11.62 kJ mol-1, respectively. It is found that the overall change in enthalpy (HHL) and entropy (SHL) for the spin transition in the presence of OEEFs decreases upon increasing the strength of the applied field. The computed spin-transition temperature (T1/2) using DFT was found to be in close agreement with the experimentally reported values. It is estimated that on increasing the strength of the applied electric field, the T1/2 increases significantly. While the DFT computed T1/2 values for the optimised geometry of 1, 2 and 3 were found to be 134.6 K, 159.9 K and 111.4 K respectively, at the applied field of 0.6425 V Å-1 T1/2 increases up to 187.3 K, 211.0 K and 184.4 K respectively, unveiling an hitherto unknown strategy to tune the T1/2 values. A limited benchmarking was performed with five additional exchange-correlation functionals: PBE, BLYP, B3LYP*, B3LYP, and PBE0. These functionals were found to be unsuitable for predicting the correct SCO behaviour for complex 2, and their behaviour under various electric fields did not improve. This emphasises the importance of choosing the correct functional at zero OEEF prior to testing them under various electric fields. Furthermore, calculations were performed with complex 1 adsorbed on the Au(111) surface. The formation of an Au-S bond during adsorption significantly stabilises the low-spin (LS) state, hindering the observation of spin-crossover (SCO) behaviour. Nonetheless, the application of an OEEF reduces this gap and brings the T1/2 value closer to the desired temperature. This offers a novel postfabrication strategy for attaining SCO properties at the interface. [ABSTRACT FROM AUTHOR]

Potassium borate glass has great potential as an ion transport material. The ion transport rate is closely related to the microstructure of the glass. However, the disorder and variations in boron and oxygen atom types in the glass structure pose challenges in the analysis of this complex glass structure. In this work, the structure of potassium borate glass was unveiled through the neutron diffraction method and ab initio molecular dynamics (AIMD) simulations. The B–O, K–O, and O–O atomic interactions, bond lengths, coordination numbers, cavity distribution, ring structure distributions and other detailed information in the microstructure of potassium borate glass were obtained. By comparing the structure and properties of potassium borate glass with those of crystals of similar components, it is found that the bond lengths of 3B–BO (BO, bridging oxygen), 4B–BO and 3B–NBO (NBO, non-bridging oxygen) are longer than those of corresponding crystals, so the structure of the boron–oxygen network is looser and the density is smaller than that of similar crystals. Moreover, we found a rule that in both borate glass and crystal, the increase of NBO shortened the length of the B–O bond, and the increase of 4B increased the length of the B–O bond. The key structures affecting the transport rate of K+ were NBO, chain structure units and cavities. This work will provide reference data for designing and developing electrically conductive amorphous materials with faster potassium-ion transport rates. [ABSTRACT FROM AUTHOR]

A series of four Cd(II) complexes with 5-methyl-4-imidazolecarboxaldehyde (L) with different inorganic anions within or outside the coordination sphere of general formula: [CdCl2L2] (1), [CdBr2L2] (2), [CdI2L2] (3), and [CdL4](PF6)2·3H2O (4) was synthesized through one-step and two-step reactions, respectively. All complexes were obtained as colorless crystals without the need for recrystallization and exhibited solubility in aqueous solutions. Structural analysis revealed different coordination environments for each complex, with variations in bond lengths and angles. The crystal packing of the complexes was stabilized by hydrogen bonding and π–π stacking interactions. FT-IR analysis indicated coordination of the ligand to the metal ion, and UV-Vis studies confirmed the stability of the complexes in solution. Computational analysis has revealed the polar nature of the complexes and their favorable stability constants. Affinity studies with DNA using the switchSense technique demonstrated rapid association and dissociation processes for all complexes, with temperature-dependent binding constants. Thermodynamic analysis suggested spontaneous with positive entropy change and endothermic formation processes for the complexes. Overall, the study underscores the synthesis, examination, and interaction with DNA of Cd(II) complexes, demonstrating their promise within medicinal chemistry. [ABSTRACT FROM AUTHOR]

Atomic substitution is a promising approach for controlling structures and properties for developing clusters with desired responses. Although many possible coordination candidates could be deduced for substitution, not all can be prepared. Therefore, predicting the correlation between structures and physical properties is important prior to synthesis. In this study, regarding Keggin-type polyoxometalates (POMs) as a model cluster, the dominant factors affecting the protonation were investigated by atomic substitutions and geometry changes. The valence of Keggin-type POMs and the constituent elements of the cluster shell structure affect the charge and potential distribution, which change the protonation sites. Furthermore, the valence of Keggin-type POMs and the bond length between the core and shell structure determine the protonation energy. These factors also affect the HOMO–LUMO gap, which governs photochemical and redox reactions. These governing factors derived from actual parameters of the α-isomer of Keggin-type POMs enabled us to deduce the protonation energy of the β-isomer, which is more difficult to prepare and isolate than the α-isomer. [ABSTRACT FROM AUTHOR]

We describe a study of the influence of cryptand denticity on the structural, electronic, and electrochemical properties of UIII-containing cryptates. Two cryptands (2.2.2 and 2.2.1) are reported. The cryptand with the smaller denticity leads to negative electrochemical potentials and shorter bond lengths that are consistent with a better fit for UIII than the larger cryptand. These studies provide insight into the rational design of cryptand-based ligands for trivalent uranium. [ABSTRACT FROM AUTHOR]

A method is proposed to estimate the energetic and entropic effects of spins of neighbouring molecules on the spin transition of a mononuclear spin crossover (SCO) complex in a molecular crystal. Density functional theory (DFT) methods have been used to model the SCO material [FeII(Lnpdtz)2(NCS)2] (Lnpdtz = 2-naphthyl-5-pyridyl-1,2,4-thiadiazole) exhibiting numerous π–π interactions using a 2D arrangement of 15 molecules. The modelling considers only the effects in the crystallographical ac plane with a particularly pronounced stacking but paves the way for future work with 3D arrangements which are computational much more costly. It involves the optimisation and normal mode calculation of the molecules in a rigid matrix of both low-spin (LS) and high-spin (HS) neighbours. This procedure has been used to calculate the previously defined cooperativity parameter Hcoop (S. Rackwitz, W. Klopper, V. Schünemann and J. A. Wolny, Phys. Chem. Chem. Phys., 2013, 15, 15450). For [FeII(Lnpdtz)2(NCS)] we obtain Hcoop = 11 kJ mol−1, a value which is comparable to those found for 3D polynuclear spin crossover materials. A normal mode analysis of the optimised centrally located molecule indicates that the vibrational entropy of the spin transition is somewhat higher (5 J K−1 mol−1) for the LS to HS transition in the LS matrix than in the HS one. The calculations show that the interactions with the neighbours influence the low-frequency modes with wave numbers <65–70 cm−1. These cause the main difference in the vibrational entropy of the spin transition for the vicinity of high- and low-spin molecules. Furthermore, a deformation of the coordination sphere of the central molecule is observed when the spins of the surrounding centres are switched. This deformation is accompanied by a change in the equatorial Fe–N bond lengths. [ABSTRACT FROM AUTHOR]

In the process of handling and storage of radioactive actinides it is essential to selectively sequester the minor actinides, such as Am and Cm, through a competitive complexation process. Herein we computationally designed two core modified ligands (L21− and L3) through systematic oxygen substitution at the NH sites of dipyriamethyrin (L1_2H), a hexadentate expanded porphyrin, and studied their competitive complexation towards trivalent actinides (An = Am/Cm) from their trichlorides using density functional theory (DFT). We observed shorter An–N bonds and longer An–O bonds in complexes based on core modified ligands (L21− and L3). The An–Cl bond length increases with increasing axial coordination number (i.e., from L12− to L3) to accommodate the ligands. All the bonds were identified to be electrostatic in nature. L12− exhibits shorter bonds and larger bond orders on complexing with Am than with Cm. On moving from complexes of L21− to L3, the An–N bond lengths are shortened, while An–O bond lengths become larger. Between the complexes of Am and Cm, there is marginal difference in their bond distances with L21− and L3. Charge analysis shows ligand to metal charge transfer during coordination, with back-donation from An to N/O and Cl. The calculated spin-density analysis indicates that An remains in its trivalent oxidation state on complexation, while orbital occupation analysis shows that the 5f and 6d orbitals are involved in bonding; this was confirmed by molecular orbital (MO) analysis that shows the complexes of L21− and L3 to exhibit higher degeneracy in their overlapping MOs. Further, the energy decomposition analysis (EDA) confirms that all ionic bonds are primarily due to electrostatic contributions, where the orbital contributions increase from L12− to L3 complexes and maximum covalency was observed in Cm complexes due to the energy matching between the 5f orbitals of Cm and the 2p orbitals of N and Cl, compared to Am. To confirm the competitiveness in the complexation of the ligand towards Am vs. Cm, the thermodynamic parameters were analysed for the ligand and metal substitution reactions. L12− shows more affinity towards Am than Cm, while L21− and L3 prefer Cm. [ABSTRACT FROM AUTHOR]

We have utilised the 4,6-di-tert-butyl resorcinol bis(diphenylphosphinite) (POCOP) ligand for exploring its coordination ability towards group 11 metal centres. The treatment of the bidentate ligand 1 with various coinage metal precursors afforded a wide range of structurally diverse complexes 2–12, depending upon the metal precursors used. This furnishes several multinuclear Cu(I) complexes with dimeric (2) and tetrameric cores (3, 4, and 5). The tetrameric stairstep complex 4 shows thermochromic behaviour, whereas the dimeric complex 2 and tetrameric complex 3 show luminescence properties at cryogenic temperatures. Interestingly, the halide substitution reaction of the dimeric complex 2 with KPPh2 produces a unique mixed phosphine-based tetrameric Cu(I) complex, 5. Treatment of the POCOP ligand with [CuBF4(CH3CN)4] in the presence of 2,2′-bipyridine afforded heteroleptic complex 6, consisting of tri- and tetra-coordinated cationic Cu(I) centres. Furthermore, we could also isolate cubane (8) and stairstep (9) complexes of Ag(I). The cationic Au(I) complex (12) was obtained from the dinuclear Au(I) complex of POCOP, 11. Complex 12 revealed the presence of a strong intramolecular aurophilic interaction with an Au⋯Au bond distance of 3.1143(9) Å. Subsequently, the photophysical properties of these complexes have been studied. All the complexes were characterised by single-crystal X-ray diffraction studies, routine NMR techniques, and mass spectroscopy. [ABSTRACT FROM AUTHOR]

Herein, we report the first set of pincer complexes 1 and 2 with the general formula [Ru(CNC)(PPh3)2Cl]Cl having a protic- and classical-NHC in the same molecule and nearly identical environments. Deprotonation of the protic-NHC complex 2 with one equivalent of base leads to the formation of anionic-NHC complex 2′. These complexes allow a direct comparison of protic- and anionic-NHCs with the classical-NHC ligand. A comparison of the molecular structure indicated that the metal carbene bond length trend is anionic-NHC > protic-NHC > classical-NHC. The electrochemical investigation revealed the electron donation tendency is classical-NHC > protic-NHC and anionic-NHC > protic-NHC. Cooperation between the metal and the ligand is indicated by the reaction of 2′ with H2 gas at 1 atm pressure and 110 °C to give the Ru-hydride complex 3. [ABSTRACT FROM AUTHOR]

A series of metallophthalocyanine (PcM) complexes with axial N-heterocyclic carbene ligands (NHC; 1,3-diisopropylimidazol-2-ylidene (DIP) and 1,3-dimethylbenzimidazol-2-ylidene (DMB)) were prepared and structurally characterized. PcCoII(DIP), PcZnII(DIP), and PcZnII(DMB) are five-coordinate complexes with mild dome-type Pc-ring distortions, while PcFeII(DIP)2 is six-coordinate and has a very large ruffle-type ring-distortion with respect to typical PcM(L)2 systems. The distortion is induced by the highly steric axial DIP ligands. The distortions were quantified and classified by their bond lengths and torsion angles, and according to the normal-coordinate structural decomposition (NSD) analysis. Upon ligation of the NHC, the insoluble PcM materials were solublized in common organic solvents, with typical UV-visible Q-band maxima observable between 658 and 677 nm; the increased solubility is rationalized in terms of the reduced solid-state aggregation of the complexes, attributable to the axial ligation. [ABSTRACT FROM AUTHOR]

LiCa8[CrIVN3]2N2F (Pnnm (#58), a = 17.5230(13) Å, b = 7.3379(5) Å, c = 4.9433(4) Å) is an example of a multinary nitridochromate fluoride, that provides additional information on almost elusive tetravalent nitridochromates. Shorter Cr–N bond lengths compared to those in the previously reported nitridochromates(III), as well as diamagnetic behavior and vibrational spectroscopy data suggest Cr(IV), which is in good agreement with the charge balance and crystal structure refinement. According to band structure calculations, LiCa8[CrIVN3]2N2F is a semiconductor with a band gap of 1.1 eV. The compound features trigonal planar [CrN3]5− units of Cs symmetry, and lithium, calcium, nitrogen and fluorine atoms arranged in a fragment of the rock salt type structure. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of the first sulfur-containing derivatives of the C,C-biscarborane {ortho-C2B10}2 cluster – thiol, thioether, and disulfide – are reported. The biscarboranyl dithiol (1-HS-C2B10H10)2 exhibits an exceedingly long intracluster carbon–carbon bond length of 1.858(3) Å, which is attributed to the extensive interaction between the lone pairs of the thiol groups and the unoccupied molecular orbital of the carborane cluster. The structures of the doubly deprotonated biscarboranyl dithiolate anion (1-S-C2B10H10)22− with various counter cations feature an even longer carbon–carbon bond length of 2.062(10) Å within the cluster along with a short carbon–sulfur bond of 1.660(7) Å, both indicative of significant delocalization of electron density from the sulfur atoms into the cluster. [ABSTRACT FROM AUTHOR]

At present, tuning the luminescence characteristics of phosphors by external physical stimuli such as temperature and pressure has attracted the interest of researchers. However, the emission-tunable luminescence processes by temperature or pressure in lead-free perovskite with ordered vacancy materials have not been systematically studied. In this study, Bi3+-doped Rb2SnCl6 crystals were successfully synthesized using a simple precipitation method, and these crystals demonstrated a remarkable enhancement of luminescence intensity compared with the unannealed ones at 140–200 °C, and with a red-shift in the emission peak from 450 to 500 nm. It was found that the annealing treatment increased the Bi–Cl bond length leading to emission red-shift and achieved the change in the emission intensity due to the band gap modulation of the material. Furthermore, a candidate material for the color-changing optical security strategies was obtained by combining the Bi3+-doped Rb2SnCl6 phosphor and printing ink. This work is a valuable reference for the rational design of luminescent perovskites with promising new functionalities and stimulates the great potential of luminescent perovskites in developing promising phosphors for advanced anticounterfeiting. [ABSTRACT FROM AUTHOR]

Despite extensive research on the photoluminescence properties of Bi3+ ions, the origins of their emission and excitation bands remain elusive. Herein, we present a comprehensive analysis of the photoluminescence properties of Bi3+-activated LuXnGaO4 (Xn = Mg, Zn), elucidating the underlying factors governing the intra-ionic and extra-ionic electronic transitions. By integrating crystal structure data and spectroscopic data analyses with semi-empirical formula calculations, the origins of excitation and emission states were elucidated. Moreover, the impact of alterations in chemical surroundings on the luminescence of Bi3+ was investigated. Both LuXnGaO4:Bi3+ phosphors exhibit three excitation peaks in the near ultraviolet region and display a broadband yellow emission. However, the luminous behavior of LuMgGaO4:Bi3+ and LuZnGaO4:Bi3+ differs due to variations in the band gap, bond length and neighboring atoms. It is anticipated that the investigation of Bi3+-activated gallates presents a promising avenue for advancing wide-band and long-wavelength emitting phosphors. [ABSTRACT FROM AUTHOR]

Five decanuclear lanthanide–iron clusters, formulated as [Ln2Fe8(hmp)10(μ2-OH)4(μ3-OH)2(μ4-O)4(H2O)6]·6ClO4·xH2O (x ≈ 8, Ln = Y for 1; x ≈ 6, Ln = Dy for 2; x ≈ 6, Ln = Ho for 3; x ≈ 7, Ln = Tb for 4; x ≈ 7, Ln = Gd for 5, Hhmp = 2-(hydroxymethyl)pyridine), have been synthesized and structurally characterized. Single-crystal structural analysis reveals that the cluster consists of six face-sharing defective cubane units. Dynamic magnetic investigations indicated that cluster 2 exhibits single-molecule magnet behavior under a zero dc field eliciting an effective energy barrier of Ueff = 17.76 K and a pre-exponential factor of τ0 = 7.93 × 10−8 s. Investigation of the performance of a series of FeIII–DyIII SMMs indicates that the relatively low energy barrier in 2 is associated with the weak ferromagnetic coupling between FeIII and DyIII ions, while the strength of ferromagnetic interaction in these clusters is mainly related to the bond distances between DyIII and O atoms coordinated to FeIII ions. Clusters 3 and 4 exhibit similar dual relaxation pathways under their respective optimal external applied dc field, where the direct relaxation process occurs in the low-frequency area, which impedes the extraction of the Ueff, while the secondary relaxation process appears at a higher frequency, which is probably a connection with intermolecularly driven relaxation. Our findings offer a magneto-structural correlation model for further investigating the single-molecule magnet behavior in lanthanide–iron systems. [ABSTRACT FROM AUTHOR]

Crystallographic investigations of eight homoleptic N,N′-dimethylpropyleneurea (dmpu) coordinated metal ions in the solid state, [Mg(dmpu)5]I2 (1), [Ca(dmpu)6]I2 (2), [Ca(dmpu)6](ClO4)2 (3), [Ca(dmpu)6](CF3SO3)2 (4), [Sr(dmpu)6](CF3SO3)2 (5), [Ba(dmpu)6](CF3SO3)2 (6), [Sc(dmpu)6]I3 (7), and [Pr(dmpu)6]I(I3)2 (8), and the complex [CoBr2(dmpu)2] (9) as well as the structures of the dmpu coordinated calcium, strontium, barium, scandium(III) and cobalt(II) ions and the cobalt(II) bromide complex in dmpu solution as determined by EXAFS are reported. The methyl groups in the dmpu molecule are close to the oxygen donor atom, causing steric restrictions, and making dmpu space-demanding at coordination to metal ions. The large volume required by the dmpu ligand at coordination contributes to crowdedness around the metal ion with often lower coordination numbers than for oxygen donor ligands without such steric restrictions. The crowdedness is seen in M⋯H distances equal to or close to the sum of the van der Waals radii. To counteract the space-demand at coordination, the dmpu molecule has an unusual ability to increase the M–O–C bond angle to facilitate as large coordination numbers as possible. M–O–C bond angles in the range of 125–170° are reported depending on the crowdedness caused by the coordination figure and the M–O bond distance. All reported structures of dmpu coordinated metal ions in both the solid state and dmpu solution are summarized to study the relationship between the M–O–C bond angle and the crowdedness around the metal ion. However, highly symmetric complexes seem to be favoured in the solid state due to favourable lattice energies. As a result, the dmpu coordinated lanthanoid(III) ions are octahedral in the solid state, while they, except lutetium, are seven-coordinate in the dmpu solution. [ABSTRACT FROM AUTHOR]

Due to the limited abundance of the actinide elements, computational methods, for now, remain an exclusive avenue to investigate the periodic trends across the actinide series. As every actinide element can exhibit a +3-oxidation state, we have explored model systems of gas-phase actinide trihalides, phosphates, and arsenates across the series to capture the periodic trends. By doing so, we were able to capture the periodic trends down the halogen series as well, and for the first time we are reporting a study on actinide astatides. Using scalar and spin–orbit relativistic Density Functional Theory (DFT) calculations, we have explored the variations in bond lengths, bond angles, and the charges on actinides (An). Despite the use of different sets of ligands, the trends remain similar. The properties of trivalent Pa, U, Np, and Pu are nearly identical; similar ionic radii could be the reason. The actinide elements show a tendency to exhibit a pre-Pu and a post-Cm behaviour, with Am acting as a switch. This could be due to the change in the behaviour from d–f-type to f-filling/d-type at around Pu–Cm in the actinides as already proposed in the previous literature. Bond lengths in the AnX3 increase down the halide series, and the atomic charges decrease on the actinide elements. [ABSTRACT FROM AUTHOR]

Nickel chloride and thiolate complexes supported by benzene–pyridine-based nonsymmetrical PCN pincer ligands, [2-(tBu2PO)-6-(2-pyrindinyl-4-R)-C6H3]NiX (R = H, CH3, CF3; X = Cl, SH, SPh), were synthesized and fully characterized. The structures of these complexes and the catalytic reactivity of the chloride complexes were investigated along with the related POCOP counterparts [2,6-(tBu2PO)2C6H3]NiX (X = Cl, SH). It was found that the composition and substitution of the pincer backbone evidently influence the structures and catalytic reactivity. The Ni–P and Ni–Cipso bond lengths in the PCN complexes are significantly shorter than those in the POCOP complex. The Ni–Cl and Ni–S bond lengths in the PCN complexes are longer than those in the POCOP complexes. An electron rich pyrindinyl ring in the PCN complexes makes the Ni–Cl bond longer. The Ni–N bond length is more sensitive to the auxiliary ligand compared with the Ni–P bond length in the PCN complexes. The PCN chloride complexes were found to be active catalysts for selective hydration of nitriles to primary amides in the presence of NaOH at 80 °C and the catalytic activity increases with the increase of electron richness of the pyridinyl ring. However, the corresponding POCOP counterpart is inactive under the same conditions. [ABSTRACT FROM AUTHOR]

In order to balance the contradiction between mesopore introduction and loss of microporosity, a surface modification strategy is proposed by selectively adsorbing organic alkaline molecules on Beta molecular sieves before NaOH etching. Organic alkaline molecules adsorb on framework aluminum sites and the protective function of organic bases is affected by the adsorption configuration and physical barrier effect of organic bases. Organic alkaline molecules serve as a protective agent to increase the bond length of Al-O bonds. Therefore, the as-synthesized hierarchical Beta molecular sieves have more acid sites due to the preservation of aluminum atoms. When employed as catalysts in the dehydration reaction of glucose, 5-hydroxymethylfurfural (5-HMF) is obtained under the synergistic effect of Brønsted and Lewis acid sites. The unique contribution is to realize the porosity regulation and alleviate the acidity loss of Beta molecular sieves. These results are important to broaden the application fields of aluminum-silicon molecular sieves especially for large molecule-engaged acid catalyzed reactions. [ABSTRACT FROM AUTHOR]

In this study, a glycerol group substituted bis(2-pyridylamino)isoindoline (BPI-OH) ligand and its metal complexes (M = Pt, Cu and Co) were synthesized. Characterization of all new compounds was carried out using FT-IR, NMR, UV-Vis, and mass spectroscopy. Various biological activities of BPI derivatives were also tested. The antioxidant activities of BPI-OH, Pt-BPI-OH, Cu-BPI-OH, and Co-BPI-OH were 87.52 ± 4.62%, 98.05 ± 5.61%, 92.20 ± 5.12%, and 89.27 ± 4.74%, at 200 mg L−1 concentration respectively. BPI derivatives displayed perfect DNA cleavage activity and plasmid DNA was completely broken at all tested concentrations. The antimicrobial and antimicrobial photodynamic therapy (APDT) activities of the compounds were investigated and BPI derivatives showed good APDT. E. coli cell viability was inhibited at 125 and 250 mg L−1. BPI-OH, Pt-BPI-OH, Cu-BPI-OH, and Co-BPI-OH also successfully inhibited the biofilm formation of S. aureus and P. aeruginosa. Furthermore, the antidiabetic activity of BPI derivatives was studied. This study also evaluates the binding affinities of four compounds (BPI-OH, Pt-BPI-OH, Cu-BPI-OH, and Co-BPI-OH) to various residues of DNA using hydrogen bond distance measurements and binding energies. The results show that the BPI-OH compound forms hydrogen bonds with residues in the major groove of DNA, while BPI-Pt-OH, BPI-Cu-OH, and BPI-Co-OH compounds form hydrogen bonds with residues in the minor groove. The hydrogen bond distances for each compound range from 1.75 to 2.2 Angstroms. [ABSTRACT FROM AUTHOR]

Hexanuclear polyoxomolybdenum-based discrete supermolecules Nax[MoV6O6(μ2-O)9(Htrz)6−x(trz)x]·nH2O (x = 0, n = 15, 1; x = 1, n = 12, 2; x = 2, n = 10, 3; x = 2, n = 49, 4; Htrz = 1H-1,2,3-triazole) have been prepared and fully characterized with different amounts of sodium cations inside and outside the intrinsic holes. Structural analyses demonstrate that they all exist a triangular channel constructed by six molybdenum–oxygen groups with inner diameters of 2.86 (1), 2.48 (2), and 3.04 (3/4) Å, respectively. Zero, one, or two univalent enthetic guest Na+ have been hosted around the structural centers, which reflect the expansion and contraction effects at microscopic level. Water-soluble species can serve as crown ether-like metallacycles before and after the sodium binding. Diverse nanoscale pores are further formed through intermolecular accumulations with hydrogen bonding. Gas adsorption studies indicate that 2–4 can selectively adsorb CO2 and O2 but have little or even no affinities toward H2, N2, and CH4. Theoretical calculations corroborate the roles of Na+ and auxiliary ligand with different states in bond distances, molecular orbitals, electrostatic potentials, and lattice energies in these discrete clusters. The binding orders of sodium cations in 2–4 are similar with the classical crown ethers, where 2 is the strongest one with 2.226(4)av Å for sodium cation bonded to six O atoms. [ABSTRACT FROM AUTHOR]

Five new compounds of formula [LnII(Mentpa)2](BPh4)2 (Ln = Eu, n = 0 (1-Eu), n = 2 (2-Eu) and n = 3 (3-Eu); Ln = Yb, n = 0 (1-Yb) and n = 2 (2-Yb); tpa = tris(2-pyridylmethyl)amine, n = 0–3 corresponds to successive methylation of the 6-position of the pyridine rings of Mentpa) have been synthesized and their structural, photophysical and electrochemical properties investigated. The LnII ions in the five complexes possess cubic coordination geometry and exhibit only small structural differences, due to the lengthening of the Ln–N bonds to accommodate the additional steric bulk associated with increasing methylation of the Mentpa ligands. Photophysical studies indicate moderate shifts in absorbance, emission and excitation bands associated with the 4f7 ↔ 4f65d1 (EuII) and 4f14 ↔ 4f135d1 (YbII) transitions, while electrochemistry reveals modulation of the redox potential of the LnII to LnIII oxidation. There is a strong correlation between Ln–N bond lengths and both the photophysical transition energies and metal redox-potentials, revealing how subtle ligand changes and ligand field effects can be used to modulate the electronic properties of complexes of divalent lanthanoid ions. Utilization of these insights may ultimately afford design and property tuning strategies for future functional molecular complexes based on divalent lanthanoid metals. [ABSTRACT FROM AUTHOR]

A series of complexes L22-M (L2: 6,6"-bis(4-methoxyphenyl)-4'-phenyl-2,2':6',2"-terpyridine, M: Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+) were synthesized by coordinating p-methoxyphenyl 6,6"-substituted terpyridine ligand with first-row transition metal ions and characterized by NMR, ESI-MS, and X-ray single crystal diffraction techniques. Single-crystal structures demonstrated that the steric hindrance of p-methoxyphenyl substituents endowed complexes L22-M with obvious longer coordination bond lengths and larger bond angles and dihedral angles compared with unmodified L12-M (L1: 4'-phenyl-2,2':6',2"-terpyridine). The chiral helix geometry was observed for L22-M, in which 2,2':6',2"-terpyridine moiety dramatically twisted to a spiral form in comparison to the nearly coplanar structure of the parent L12-M, resulting in plentiful intramolecular and intermolecular π- π interactions. Also, the appealing racemic (P and M) double helix packed structure for 6,6"-modified bisterpyridine complex L22-Cu was formed in the crystal. The consequent appealing charge transfer (CT) emission for L22-Zn in the solution and solid were investigated via UV-vis and fluorescence spectroscopy techniques and time-dependent density functional theory (TD-DFT) calculations. This work afforded a new method to achieve intriguing chiral geometry and CT optical properties via the subtle design and modification of terpyridine ligands. [ABSTRACT FROM AUTHOR]

Zirconocene cations react with Cp2WH2 affording the bimetallic [Cp2Zr(μ-H)(μ–η1:η5-C5H4)WHCp]+ bridging hydride 1 (Cp = cyclopentadienyl anion, C5H5−) via σ-bond metathesis. Complex 1 features an atypical out of plane Zr(μ-H)W moiety, where no intermetallic interaction is involved, and a fluxional core. Coordination geometry and bond distances of the bridging hydride interaction can be modulated upon reaction with Lewis bases and unsaturated substrates. PMe3, P(p-tol)3, 3,5-dimethylpyridine and THF bind to 1 and shift the hydride bridge on the coordination plane of Zr. Insertion of olefins and alkynes into the Zr–C bond of 1 leads instead to alkyl and vinyl species where the Zr and W coordination planes are perpendicular to each other. Such alterations of the Zr(μ-H)W arrangement are reflected in the average 1H NMR chemical shift values of the hydride, which correlate linearly with computed Zr–H distances. Reactivity experiments with H2 showed that the bridging hydride interaction prevents bimetallic cooperativity and that σ-bond metathesis between Zr–C and H–H bonds is the preferred pathway for all the investigated complexes. [ABSTRACT FROM AUTHOR]

The effect of point defects on the performance of the Li3InCl6 solid electrolyte was investigated using first-principles simulations. The Li-ion conductivity of Li3InCl6 was improved by the presence of point defects, such as a 4g site occupation by In or a Cl vacancy. The diffusion of Li ions was activated by the movement of some Li ions to vacant sites in the In layer, and the point defects reduced the energy barrier of this step, resulting in an overall increase in Li-ion diffusivity. The underlying mechanism of this effect was examined in terms of the structural and chemical properties of Li–Cl and In–Cl bonds, which indicated the energy barrier was closely related to changes in the bond distance and covalent interaction between the migrating Li and nearby Cl ions and nonuniformity among In–Cl bonds. Thermodynamic analysis showed that defect formation was unfavorable during conventional high-temperature synthesis; therefore, it is suggested that heating is applied at low temperatures only as a supplementary process to modify the crystallinity after preparing defective Li3InCl6 crystals by mechanical or solution-based routes to practically implement the effect of point defects and improve the solid electrolyte performance of Li3InCl6. [ABSTRACT FROM AUTHOR]

A series of Ni(II) complexes with pyridine-based macrocyclic ligand L (3,12,18-triaza-6,9-dioxabicyclo[12.3.1]octadeca-1(18),14,16-triene) with general formula [Ni(L)(X)2]0/2+ (X = Br− (1), I− (2), CH3CN (3), NCS− (4), imidazole (5)) was prepared and thoroughly investigated. X-ray molecular structures confirmed pentagonal bipyramidal geometry for all studied complexes with a strong Jahn–Teller distortion in the pentagonal equatorial plane and significantly elongated Ni–O distance(s) with a decrease of this distortion by varying axial coligands (CH3CN > Br− > I− > NCS− > imidazole). Direct current magnetic measurements revealed the easy-axis type of magnetic anisotropy with negative as well as positive axial zero-field-splitting parameter D ranging from +6.8 to −14.5 cm−1, which remains not affected in the halogenido series Cl− → Br− → I−, but which increases in the series with N-axial ligands in order CH3CN → NCS− → imidazole. Theoretical calculations helped to elucidate (i) the final coordination numbers 6 + 1 for 1 and 2, and 5 + 2 for 2–5, (ii) the pattern of splitting of d-orbitals, contributions of excited states to the final D-values and their final signs, and (iii) the complexity in the variation of the D and E parameters with elongation of axial bond distances in such strongly distorted systems. The studied complexes did not show any alternating magnetic susceptibility signal, but it was clearly documented that the magnetic anisotropy of the pentagonal bipyramidal Ni(II) complexes can be modulated/tuned by variation of axial coligands. Nevertheless, great care has to be taken for symmetry of the equatorial ligand field. [ABSTRACT FROM AUTHOR]

Silanones (O＝SiR2) are highly reactive species that readily convert to oligomeric siloxane (O–SiR2)n. The coordination of silanones to transition metal fragments to afford silanone-coordinated complexes is a reliable silanone stabilization method. Herein, a pyridine-stabilized silanone molybdenum complex Cp*(OC)2Mo{O＝SiMes2(py)}(SiMe3) (2b, Cp*: η5-C5Me5, Mes: 2,4,6-Me3C6H2, and py: pyridine) was synthesized by reacting the silyl(silylene) complex Cp*(OC)2Mo(＝SiMes2)(SiMe3) (4b) with pyridine-N-oxide in pyridine. X-ray crystal structure analysis revealed that the geometry of complex 2b is similar to those of the previously synthesized DMAP-stabilized analogue Cp*(OC)2Mo{O＝SiMes2(DMAP)}(SiMe3) (2a, DMAP: 4-(dimethylamino)pyridine). The Si＝O and Mo–O bond distances in 2b are similar to those observed in 2a, but the N–Si coordination bond of 2b is slightly longer (approximately 0.05 Å) than that of 2a, indicating weaker pyridine coordination than that of DMAP. The reaction of 2a with excess PMe3 in C6D6 at room temperature for 28 h afforded Cp*(OC)2Mo(PMe3)(SiMe3) (5c) in a 43% NMR yield. In contrast, reacting 2b with excess PMe3 in C6D6 at room temperature for 9 h afforded 5c and the five-membered metallacyclic carbene complex Cp*(OC)Mo(＝C(SiMe3)OSiMes2O)(PMe3) (6) in 10% and 41% NMR yields, respectively. The reactions of pyridine-stabilized silanone complexes Cp*(OC)2M(O＝SiMes2(py))(SiMe3) (M = Mo (2b) and W (1b)) with acetone proceeded via pyridine elimination, coordination of acetone to the Si center in the silanone ligand, and elimination of HSiMe3 to give Cp*(OC)2M{OSiMes2OC(Me)＝CH2} (M = Mo (8) and W (9)) in high yields. [ABSTRACT FROM AUTHOR]

The effect of point defects on the performance of the Li3InCl6 solid electrolyte was investigated using first-principles simulations. The Li-ion conductivity of Li3InCl6 was improved by the presence of point defects, such as a 4g site occupation by In or a Cl vacancy. The diffusion of Li ions was activated by the movement of some Li ions to vacant sites in the In layer, and the point defects reduced the energy barrier of this step, resulting in an overall increase in Li-ion diffusivity. The underlying mechanism of this effect was examined in terms of the structural and chemical properties of Li–Cl and In–Cl bonds, which indicated the energy barrier was closely related to changes in the bond distance and covalent interaction between the migrating Li and nearby Cl ions and nonuniformity among In–Cl bonds. Thermodynamic analysis showed that defect formation was unfavorable during conventional high-temperature synthesis; therefore, it is suggested that heating is applied at low temperatures only as a supplementary process to modify the crystallinity after preparing defective Li3InCl6 crystals by mechanical or solution-based routes to practically implement the effect of point defects and improve the solid electrolyte performance of Li3InCl6. [ABSTRACT FROM AUTHOR]

We provide definitive experimental proof that the archetypal string-like compound [Cr5(tpda)4(NCS)2] has alternating long and short Cr–Cr separations in the solid state, as conjectured by F. A. Cotton, rather than essentially equally spaced Cr atoms, as initially claimed (H2tpda = N2,N6-di(pyridin-2-yl)pyridine-2,6-diamine). Single-crystal X-ray data collected from 292 to 3 K revealed that the misinterpretation is caused by pseudo-merohedral twinning and that bond length alternation is enhanced at low temperature. [ABSTRACT FROM AUTHOR]

The tridentate pincer ligand [LONS]3− with the ONS donor set was generated in situ by cleaving the disulfane linkage of the pristine redox-active H4Sar(AP/AP) ligand during the complexation reaction with Co(II) and Mn(II) salts in the presence of air and Et3N. X-ray crystal structure analysis of the Co complex (1) and Mn complex (2) revealed that both the complexes were neutral in charge and six-coordinate with the meridional coordination of the two pincer [LONS]n− ligands. The Co ion was in the trivalent state, while the Mn ion was in the tetravalent state. Thus, the generated two pincer [LONS]3− ligands were non-innocent and cumulatively were in trinegative and tetranegative charges for the respective complexes. The intraligand bond distances of the coordinating ligands in each complex were similar, implying the same oxidation/electronic structure of the two ligating units. Variable-temperature magnetic susceptibility measurements revealed an S = 1/2 ground state for each complex. X-band EPR measurements unambiguously established the presence of a ligand-based unpaired electron in complex 1, and in complex 2, the unpaired electron was at the Mn centre. DFT-based theoretical calculations suggested the three-electron oxidation of the two ligating units in complex 1. Two iminosemiquinone radicals were of opposite spins (α-spin and β-spin) and a thiyl radical in either α-spin or β-spin was delocalized between two sulfur atoms. Thus, the antiferromagnetic coupling among the two opposite spins provided an S = 1/2 ground state and resulted in the radical-based EPR spectrum. In complex 2, each ligating pincer unit contained an iminosemiquinone radical that interacted antiferromagnetically with the Mn(IV)-based three unpaired electrons. This rendered a doublet ground state with the residual electron density located at the Mn center. [ABSTRACT FROM AUTHOR]

This document is a back cover of an article featured in the journal "Dalton Transactions: An International Journal of Inorganic Chemistry." The article, written by Yasushi Sekine et al., focuses on the protonation of Keggin-type polyoxometalates and the factors that influence it. The research was conducted at Waseda University in Tokyo, Japan. The article also mentions another paper by Yuichi Kitagawa et al., which discusses the effective photosensitized emission of a Tb(III) complex. The document provides information about the authors, the topics covered in the articles, and the journal's publication details. [Extracted from the article]

Herein we report a series of CuI complexes supported by tetradentate RN4 pyridinophane ligands that coordinate to ethylene forming either mononuclear complexes with ethylene coordinated in an η2-mode or a binuclear complex where ethylene binds to two Cu atoms in a μ-η2-η2-mode, depending on the steric effects of the RN4 ligand and the reaction conditions. In the binuclear complex with bridging ethylene, the C＝C bond is significantly elongated, with a bond length of 1.444(8) Å according to X-ray diffraction analysis. This complex represents the only examination a μ-η2-η2-coordinated Cu–olefin complex reported to date, featuring one of the longest reported C＝C bonds. The spectroscopic characterization, structure, electrochemical properties and solution behavior are analyzed in this study. Coordination of ethylene was found to be reversible in these complexes and more favored in less sterically hindered RN4 ligands, so that ethylene binding is observed in a coordinating solvent (MeCN) environment. In the case of the MeN4 ligand, the ethylene complex is photoluminescent in the solid state. The ethylene binding modes in mono- and binuclear complexes are elucidated through Natural Bond Orbital and QTAIM analyses. [ABSTRACT FROM AUTHOR]

A series of small, middle, and large anatase TiO2 particles were synthesized through the hydrolysis of titanium tetraisopropoxide (TTIP) to investigate the size-related chemical bond length and strength variation. Unit cell volume contraction with decreasing particle size is identified from Rietveld refinement of high-resolution synchrotron powder X-ray diffraction (PXRD) patterns. More titanium vacancies are also found for smaller anatase particles. Contrary to the variation in unit cell volume, a larger Debye temperature ΘD(TiO2) derived from the linear and nonlinear fitting of atomic displacement parameters (Uiso(TiO2)) as a function of temperature is revealed for smaller anatase particles. The length of the Ti–O bond is also shorter for smaller anatase particles. Furthermore, optical phonon frequencies blue-shifting with the decrease in anatase particle size are determined by Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) analysis rules out the presence of a large amount of Ti3+, while optical diffuse reflectance measurement eliminates the existence of a large number of oxygen vacancies in all particles. Combining the analysis results of PXRD, thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR), more structural and surface hydroxyls (–OH) appear to exist in smaller anatase particles. It is the structural and surface –OH that are responsible for the size-related chemical bond length and strength variation in the as-synthesized anatase particles. [ABSTRACT FROM AUTHOR]

A series of small, middle, and large anatase TiO2 particles were synthesized through the hydrolysis of titanium tetraisopropoxide (TTIP) to investigate the size-related chemical bond length and strength variation. Unit cell volume contraction with decreasing particle size is identified from Rietveld refinement of high-resolution synchrotron powder X-ray diffraction (PXRD) patterns. More titanium vacancies are also found for smaller anatase particles. Contrary to the variation in unit cell volume, a larger Debye temperature ΘD(TiO2) derived from the linear and nonlinear fitting of atomic displacement parameters (Uiso(TiO2)) as a function of temperature is revealed for smaller anatase particles. The length of the Ti–O bond is also shorter for smaller anatase particles. Furthermore, optical phonon frequencies blue-shifting with the decrease in anatase particle size are determined by Raman spectroscopy. X-ray photoelectron spectroscopy (XPS) analysis rules out the presence of a large amount of Ti3+, while optical diffuse reflectance measurement eliminates the existence of a large number of oxygen vacancies in all particles. Combining the analysis results of PXRD, thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR), more structural and surface hydroxyls (–OH) appear to exist in smaller anatase particles. It is the structural and surface –OH that are responsible for the size-related chemical bond length and strength variation in the as-synthesized anatase particles. [ABSTRACT FROM AUTHOR]

Solids that change their thermal conductivity during a phase transition can be useful in the development of a thermal switch to allow control of heat flow and reduce energy consumption. Although a crystal of a spin crossover (SCO) complex is a representative solid with spin states correlated with heat transporting lattice vibrations, the heat transporting property of a crystal of the SCO complex during a spin state transition has not yet been reported. In this work, we report that the temperature dependence of the thermal conductivity of mononuclear Fe(III) SCO complexes is greatly affected by spin state transitions. It was found that the thermal conductivity was minimized at temperatures near the beginning edge of the spin state transitions, and the product of the velocity and the mean free path of phonons also reached a minimum close to the temperature at which the spin state transition progressed by 50%. These findings suggest that the spin state transitions accompanying the coordination bond length elongation and lowering of the vibration energy are allowed at a temperature where the mean-free path of phonons is minimized to the extent of intermolecular distances. These findings also indicate that SCO complexes reported in the literature are promising candidates for heat transportation switch materials. [ABSTRACT FROM AUTHOR]

The coordination mode of the BH4− ligand in transition metal tetrahydroborate complexes is mainly dominated by the nature of the metal centres. However, other factors can also play important roles sometimes. In order to rationalize the coordination modes and the stability of the BH4− ligand in group 10 metal tetrahydroborate pincer complexes, [2,6-(tBu2PO)2C6H3]Pt(η1-HBH3) and [C6H4-o-(NCH2PtBu2)2B]M(η2-H2BH2) (M = Ni, Pt) were prepared and characterized. A structural comparison of [2,6-(tBu2PCH2)2C6H3]Ni(BH4), [2,6-(tBu2PO)2C6H3]M(BH4) and [C6H4-o-(NCH2PtBu2)2B]M(BH4) (M = Ni, Pd, and Pt) indicates that the M–P bond length, the P–M–P bite angle and the trans-influence of the central atom in the pincer platform also affect the coordination mode of the BH4− ligand. The nickel complexes tend to adopt a monodentate coordination mode while the palladium and platinum complexes can adopt either the monodentate or the bidentate mode depending on the structural features of the pincer platforms. Longer M–P bonds and smaller P–M–P bite angles favour the bidentate mode. The stability of the BH4− ligand is influenced by both the coordination mode and the nature of the metal centre. The BH3 species is released more easily from complexes with less electron rich metal centres. Following the series of Ni, Pd, and Pt, complexes with the same pincer ligand more easily lose a BH3 moiety. [ABSTRACT FROM AUTHOR]

The report on phosphaphthalimide (1), the phosphorus analogue of the phthalimide anion, dates back to forty years ago. However, the presence of π-delocalization between two-coordinated phosphorus centre and neighbouring carbonyl groups in 1 has been underestimated. Herein, sodium salts of 1 were obtained through a convenient procedure on a relatively large scale with a modified procedure. Reactivity studies demonstrated that 1 is indeed a good electrophile and the essential role of π-delocalization in 1 controlling its ambident properties. NBO analysis revealed the p–π conjugation and p–σ* hyperconjugation in 1 affecting its bond lengths in opposite ways. [ABSTRACT FROM AUTHOR]

Heterobimetallic Ln(III)–Pd(0) complexes (Ln = Y, Sm, Gd, Yb) featuring tetranuclear structures with COD as bridges were obtained via the metallation of tris(phosphinoamido) rare-earth metal complexes [Ph2PNAd]3Ln (Ad = adamantyl) with (COD)Pd(CH2SiMe3)2. Notably, the Sc(III)–Pd(0) complex possesses a C3-symmetry with a very short Sc–Pd bond length of 2.432(2) Å, while the tetranuclear complexes exhibited versatile structures both in solution and in the solid state. Reduction of the trivalent complex (Ph2PNAd)3Yb with one equivalent of KC8 in the presence of 18-c-6 afforded the divalent complex [(Ph2PNAd)3Yb][(18-c-6)K(THF)2], which was further reacted with (Ph3P)4Pd to form the first Yb(II)–Pd(0) complex. The Pd(0) → Yb dative interaction weakened significantly from Yb(III) to Yb(II) based on computational studies, which was attributed to the attenuated Lewis acidity of the Yb(II) center. Reactions of Ln(III)–Pd(0) complexes (Ln = Sc and Yb) with the disulfide PhSSPh showed that the Pd(0) center served as a two-electron donor while the reaction apparently occurred on the Ln(III) centers to form Ln(III)–Pd(0) bis-sulfide complexes. [ABSTRACT FROM AUTHOR]

Through a mixed-ligand strategy, the structural change from a discrete dinuclear DyIII cluster to a one-dimensional polymeric chain was achieved, maintaining the two magnetic entities with the same {Dy(dppbO2)2(H2O)5} (dppbO2 = 1,4-butylenebis(diphenylphosphine oxide)) core structure. Since the hydrogen bonding between the equatorial coordinated water molecules and the guests/solvents/anions is distinct, the local geometry and the equatorial planarity of the first coordination sphere of the central DyIII ion become slightly different caused by the second coordination sphere. As a result, the dinuclear compound shows typical butterfly-shaped hysteresis loops, while it significantly opens at zero magnetic field up to 11 K for the 1D polymer, which is unprecedented in coordination polymers. Our experimental observations and theoretical analysis indicate that the hydrogen bonding leads to the fine-tuning of certain bond lengths and angles of the coordination environment, as well as the crystal field to a certain extent, revealing that the second coordination sphere affects the first coordination sphere by hydrogen bonding. [ABSTRACT FROM AUTHOR]

A potential connection has previously been proposed between the emergence of unexpected covalent behaviour in various transcurium complexes and the increasing stability of the +2 oxidation state in the later members of the actinide series. We recently used computational methods to study AnCl3, finding evidence for energy degeneracy driven covalency in the later actinides, and here present a comparative study of AnCl2. The An--Cl bond lengths of the latter divide into two data sets; Th--Np, Cm, Bk and Pu, Am, Cf--No. On average the An--Cl bond length decreases for both sets but, with significant increases between Np and Pu, and between Bk and Cf, unlike the former group (Pu, Am, Cf--No)Cl2 have significantly larger lengths than the corresponding trichlorides. Using a range of Natural Bond Orbital (NBO), Natural Resonance Theory (NRT) and Quantum Theory of Atoms In Molecules (QTAIM) metrics, the covalency of the dichloride bonds is analysed. We find that the first group of dichlorides are similar to their trichloride counterparts and possess significantly more covalent bonds than (Pu, Am, Cf--No)Cl2. We believe this change in covalent behaviour across the series for the dichlorides is due to a decreased involvement of the 6d orbital in the later elements (as a result of the f--d excitation energy exceeding the d-stabilisation energy of the actinide ions in question). Moreover, we find that unlike the trichlorides, where the QTAIM delocalisation index indicates that covalency plateaus/moderately increases, An--Cl covalency decreases across the second half of the series for AnCl2. We attribute this difference in behaviour to a lack of significant energy degeneracy driven covalency for the dichlorides, with the energy difference between the dichlorides' β 5f and 3p Natural Atomic Orbitals being larger than for the trichlorides. Hence we find it is not the presence of a stable +2 oxidation state, but instead the extent of energy matching between the actinide 5f orbitals and the ligand 3p, that drives covalency in the transcurium chlorides. [ABSTRACT FROM AUTHOR]

Amidinate compounds with stabilized aluminium(II) and gallium(II) elements of composition L2M2X2 (3 and 4) have been prepared from their LMX2 (1 and 2) precursor, where M = Al (1 and 4) and Ga (2 and 3); L = PhC(NiPr2C6H3)2 (1 and 4) and PhC(NtBu)2 (2 and 3); and X is I (1 and 4) and Cl (2 and 3) and insights into their bonding are gained. The M–M bond lengths are reported along with the single-crystal X-ray structures of 1–4. [ABSTRACT FROM AUTHOR]

Doping Gd2LuAl5O12:Ce with a Ca2+/Si4+ pair produced a series of Gd1.97−xLuCaxAl5−xSixO12:0.03Ce (x = 0.0–1.2) garnet new phosphors, and remarkable regulation of the crystal structure and Ce3+ luminescence was achieved. Rietveld refinement and spectral analysis revealed that greater incorporation of Ca2+/Si4+ led to a higher lattice rigidity by cell contraction, a narrower bandgap, a longer average bond length/less distortion of the [CeO8] dodecahedron and decreased centroid shift/crystal field splitting of the Ce3+ 5d energy level. A blue-shifted 4f–5d1 transition, a narrower emission band, improved thermal stability of luminescence and a shorter fluorescence lifetime were observed with increasing Ca2+/Si4+ content. Applying the yellowish-green-emitting Gd0.77LuCa1.2Al3.8Si1.2O12:0.03Ce optimal phosphor (x = 1.2), together with a commercial CaAlSiN3:Eu red phosphor, in 450 nm-excited LED lighting produced a low CCT of ∼3625 K and a high CRI/R9 of ∼95.2/94.8, indicating that the phosphor has application potential in high-performance w-WLED. [ABSTRACT FROM AUTHOR]

Herein, we report a distinct Cr–Cr sextuple bond with an ultra-short length stabilized by equatorial alkali metals. Bonding analyses indicate that the two desired 4p–pi bonds failed to be formed but the bonding strength is enhanced due to the introduction of alkali metals, weakening the Cr–Cr 4s–4s effect. The Cr–Cr sextuple bond comprises five explicit 3d–3d overlaps and another delocalized σ bond. [ABSTRACT FROM AUTHOR]

Metal complexes exhibiting multiple reversible redox states have drawn continuing research interest due to their electron reservoir features. In this context, the present article describes ruthenium-acac complexes (acac = acetylacetonate) incorporating redox-active azo-derived abim (azobis(1-methylbenzimidazole)) in mononuclear [RuII(acac)2(abim)] (1) and dinuclear [{RuIII(acac)2}2(μ-abim2−)] (2)/[{RuIII(acac)2}2(μ-abim˙−)]ClO4 ([2]ClO4) frameworks. Structural, spectroscopic, electrochemical, and theoretical analysis of the complexes revealed the varying redox states of the azo functionality of abim, i.e., [–N＝N–]0, [–NN–]˙−, and [–N–N–]2− in 1, [2]ClO4, and 2, respectively. Comparison between the calculated azo bond distances of analogous {Ru(acac)2}-coordinated azoheteroaromatics, i.e., abim and previously reported abbt (azobis(benzothiazole)) and abpy (azobis(pyridine)) examples, revealed the impact of varying amounts of intramolecular metal-to-azo electron transfer (i.e., the case of back-bonding) on stabilising radical anionic ([–NN–]˙−) and hydrazido ([–N–N–]2−) bridging modes in the complexes. An evaluation of the electronic forms of the complexes in accessible redox states via combined experimental and theoretical studies suggested a preferred resonance configuration rather than a precise description, primarily due to the severe mixing of metal-abim frontier orbitals. Moreover, the newly developed corresponding Cu-abim complex [Cu I2 (μ-abim)3](BF4)2 ([3](BF4)2) demonstrated the unique scenario of varying bridging modes of abim within the same molecular unit, involving both coordinated and non-coordinated azo functionalities. This also reemphasised the concept of the coordination-induced lengthening of the azo bond of abim (∼1.30 Å), via dπ(CuI) → π*(azo, abim) back-bonding, with reference to its non-coordinating counterpart (1.265(6) Å). [ABSTRACT FROM AUTHOR]

A series of iron(II) complexes with the general formula [FeII(L2-Qn)(L)]n+ (n = 1, L = F−, Cl−; n = 2, L = NCMe, H2O) have been isolated and characterized. The X-ray crystallographic data reveals that metal–ligand bond distances vary with varying ligand field strengths of the sixth ligand. While the complexes with fluoride, chloride and water as axial ligand are high spin, the acetonitrile-coordinated complex is in a mixed spin state. The steric bulk of the quinoline moieties forces the axial ligands to deviate from the Fe–Naxial axis. A higher deviation/tilt is noted for the high spin complexes, while the acetonitrile coordinated complex displays least deviation. This deviation from linearity is slightly less in the analogous low-spin iron(II) complex [FeII(L1-Qn)(NCMe)]2+ of the related asymmetric ligand L1-Qn due to the presence of only one sterically demanding quinoline moiety. The two iron(II)-acetonitrile complexes [FeII(L2-Qn)(NCMe)]2+ and [FeII(L1-Qn)(NCMe)]2+ generate the corresponding iron(IV)-oxo species with higher thermal stability of the species supported by the L1-Qn ligand. The crystallographic and spectroscopic data for [FeIV(O)(L1-Qn)](ClO4)2 bear resemblance to other crystallographically characterized S = 1 iron(IV)-oxo complexes. The hydrogen atom transfer (HAT) and oxygen atom transfer (OAT) reactivities of both the iron(IV)-oxo complexes were investigated, and a Box–Behnken multivariate optimization of the parameters for catalytic oxidation of cyclohexane by [FeII(L2-Qn)(NCMe)]2+ using hydrogen peroxide as the terminal oxidant is presented. An increase in the average Fe–N bond length in [FeII(L1-Qn)(NCMe)]2+ is also manifested in higher HAT and OAT rates relative to the other reported complexes of ligands based on the N4Py framework. The results reported here confirm that the steric influence of the ligand environment is of critical importance for the reactivity of iron(IV)-oxo complexes, but additional electronic factors must influence the reactivity of iron-oxo complexes of N4Py derivatives. [ABSTRACT FROM AUTHOR]

Neodymium (Nd), a technologically important metal ion, has emerged as a major contaminant in aquatic systems in recent years owing to its surge in electrical and electronic applications as a permanent magnet. The chelating molecules present in hydro- and biospheres could substantially enhance its absorption and lead to transportation and migration of Nd from the source. The mechanistic understanding of the Nd interaction with naturally relevant biomoieties present in flora and fauna is of primitive importance to estimate the toxicological effects of the metal ion. The present studies aimed at understanding the aquatic interaction of Nd with two biomoieties namely pyrazine-2-carboxylic acid (P2C) and pyrazine-2,3-dicarboxylic acid (P23C) by multiple experimental determinations and theoretical estimations. Potentiometry and spectrophotometry were employed to determine the aquatic speciation and thermodynamic stability of the complexes. Both techniques supported the formation of MLi (i = 1–4) complexes by Nd(III) with P2C and MLi (i = 1–3) complexes with P23C. The Nd–P23C complexes are more stable than the Nd–P2C complexes for ML formation, while the opposite trend is observed for the ML2 and ML3 complexes. Titration calorimetry was used to determine the enthalpies of complexation which was found to be exothermic and majorly favored by entropy contributions. The formation of the Nd(III)–P2C complexes is more exothermic than that of the respective Nd(III)–P23C complexes. Density functional theory was employed for the geometry optimization of the predicted complexes and for the estimation of the bond distances and partial charges on the coordinating atoms in the optimized geometries. Experimental insights provide crucial inputs at the macro (thermodynamic) level and theoretical calculations help in understanding the complexation process at the molecular level. [ABSTRACT FROM AUTHOR]

A series of mononuclear CuII complexes, [CuII(4-FBA)2(py)2(H2O)] (1), [CuII(3-FBA)2(py)2(H2O)] (2), and [CuII(3,4-F2BA)2(py)2(H2O)] (3), where 4-FBA = 4-fluorobenzoate, 3-FBA = 3-fluorobenzoate, 3,4-F2BA = 3,4-difluorobenzoate, and py = pyridine, respectively, was synthesized and the complexes crystallographically identified. All the CuII complex crystals share a one-dimensional O–H⋯O hydrogen-bonding chain substructure, although the mutual alignment of fluorinated benzoate (FxBA) ligands exhibits subtle differences among the various compounds, i.e., FxBA ligands align in an antiparallel fashion in crystals 1 and 3, while 3-FBA ligands in crystal 2 are interdigitated with a tilt along the a axis. Reversible phase transitions were found upon heating at 170.7, 171.3, and 267.5 K for crystals 1, 2, and 3, respectively; all crystals showed approximately 3% expansion and shrinkage of the intermolecular O–H⋯O hydrogen bond distances associated with the thermally activated orientational fluctuations of the FxBA ligands in crystals 1 and 3. The increase in dielectric constant with increasing temperature, at 240 K, activated molecular fluctuation in the 3,4-F2BA ligands in crystal 3. Heat capacity measurements indicated that both the expansion and shrinkage of hydrogen bonds, and the molecular fluctuation in 3,4-F2BA ligands, contributed to phase transition, and the latter caused dipole fluctuation, resulting in a dielectric anomaly in crystal 3. [ABSTRACT FROM AUTHOR]

The Ir–Si bond distances reported for Ir-(fac-κ3-NSiNOPy) and Ir-(fac-κ3-NSiN4MeOPy) species (NSiNOPy = bis(pyridine-2-yloxy)methylsilyl and NSiN4MeOPy = bis(4-methyl-pyridine-2-yloxy)methylsily) are in the range of 2.220–2.235 Å. These values are in the lowest limit of the Ir–Si bond distances found in the Cambridge Structural Database (CSD). To understand the origin of such remarkable shortening, a computational study of the bonding situation of representative examples of Ir-(fac-κ3-NSiN) species has been carried out. It is found that the Ir–Si bond can be described as an electron-sharing (i.e. covalent) bond. Despite that, this bond is highly polarized and as a result, the contribution of the electrostatic attractions to the bonding is rather significant. Indeed, there exists a linear relationship (R2 = 0.97) between the Ir–Si bond distance and the extent of the computed electrostatic interactions, which indicates that the ionic contribution to the bonding is mainly responsible for the observed Ir–Si bond shortening. [ABSTRACT FROM AUTHOR]