Metal Charge Transfer Research Articles

Synthesis, Characterization and Analysis of Leishmanicide Ability of the Compound [Ru(Cl)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>(gly)

Studies of coordinated compounds containing ruthenium (Ru2+ and Ru3+) have shown very effective in vitro results for the treatment of cancer and neglected diseases such as leishmaniasis. In this paper, we present the synthesis of the compound [Ru(Cl)3(H2O)2(gly)], which was characterized by spectroscopic (Ultraviolet-visibleand infrared) and thermal analysis (Thermogravimetry/Derived Thermogravimetry and Thermogravimetry/Differential Thermal Analysis). The analysis of the compound in the Ultraviolet-visibleregion showed a 290 nm band λmax (ε= 1.685 × 103 L·cm-1·mol-1), attributed to the ligand metal charge transfer (LMCT). The spectroscopy (IR) showed major vibrational bands at δa (-COO-) 1664 cm-1, δs (-COO-) 1388 cm-1, δs () 1571 cm-1 and δs (CCN) 889 cm-1. The thermal analysis by TG/DTG and TG-DTA indicated that the complex has five consecutive stages of decomposition: at 115°C (TG = 12.18%; Calculated = 11.32%) H2O (coordinating water), exothermic peaks at 230°C, 307°C, 440°C and 463°C due to oxidative decomposition of glycine, followed by the formation of RuClO residue at 665°C (TG = 41.11%; Calculated = 40.81%). The thermal characterization suggested the stoichiometry of the complex [RuCl3(H2O)2(gly)]. The antileishmanial capacity of this compound was also evaluated and the results indicated a 31% decrease in the parasitic infection of macrophages and a 1.5 to 3 fold reduction in the number of parasites per cell after treatment with 100 μg/mL of the complex. These results support the possible use of this compound as a therapeutic alternative against medical and veterinary parasites.

Modulating photo-luminescence of Au2Cu6 nanoclusters via ligand-engineering

The luminescence of Au2Cu6 nanocluster is controlled by tailoring the ligand to metal charge transfer via engineering the phosphine ligands.

The fluorescence properties of tiara like structural thiolated palladium clusters.

A series of tiara like structural Pdn(SR)2n (5 ≤n≤ 20) nanoclusters were synthesized by using a modified Brust-Schiffrin route and isolated via thin layer chromatography, and further measured using MALDI-MS. A new crystal structure of tiara like structural Pd6(SC2H4Ph)12 was determined by single-crystal X-ray crystallography. The atomic distance of PdPd increased and the Pd-S bond length decreased with the increase in the n value in the optimized structure of Pdn(SR)2n (5 ≤n≤ 10), which were optimized by density functional theory at the B3LYP level. All these 16 Pdn(SR)2n nanoclusters exhibit weak emission at 620 nm with single band excitation at around 268 nm. The origin of emission of this series of clusters could be illustrated by using a ligand to metal charge transfer model.

Preparation of Cu Nanocomposites from EDA, DETA, and Jeffamine Cored PAMAM Dendrimers with TRIS and Carboxyl Surface Functional Groups.

This study presents the synthesis and UV-Vis characterization of Cu nanocomposites from ethylenediamine (EDA) (E), diethylenetriamine (DETA) (D), and Jeffamine® T-403 (P) cored PAMAM dendrimers (PAMAMs) with TRIS and carboxyl surface functional groups. Cu-PAMAM dendrimer encapsulated nanoparticles (Cu-DENs) were characterized by UV-Vis spectroscopy. Disappearance of the 680 nm d-d transition and 270-300 nm ligand to metal charge transfer (LMCT) peaks and the formation of monotically increasing exponential band were used as the evidence of the successful synthesis of Cu-DENs in addition to immediate color change of dendrimer-metal mixture solutions from blue to golden brown by reduction. Synthesized Cu-DENs could be facilitated as novel alternatives to the existing nanomaterials used in a wide range of applications involving bio and chemical sensors, catalysis, hydrogenations, oxidations, semiconductors, noble metals, magnetic dendrimer nanocomposites, environmental cleanup and many others.

Structural Design of Zeolitic Cluster Organic Frameworks from Hexamethylentetramine and Copper-Halide Clusters

Zeolitic cluster organic frameworks constructed with two different tetrahedral units, hexamethylenetetramine (hmt) and hmt-type [Cu4Cl6]2– clusters, are realized in this work for the first time. By using a tetrahedral hmt ligand to assemble in situ hmt-type Cu4Cl6 clusters, a three-dimensional cluster organic framework with lonsdaleite (lon) topology is successfully built to host the two-dimensional honeycomb-like metal–organic complex. Furthermore, a series of cluster organic frameworks based on hmt and other well-defined copper-halide clusters, such as Cu2Cl3, Cu3Cl2, Cu4Cl4, Cu5Cl6, and Cu6Cl6, are also presented, which exhibit rich topological nets. These compounds are further investigated by infrared, powder X-ray diffraction, thermogravimetric analysis, infrared and photoluminescent spectroscopy. Photoluminescent studies reveal that these compounds display yellow green emissions based on halide to metal charge transfer. This work reveals a versatile synthetic method to generate a large family of copper-halide cluster organic frameworks with hmt ligands.

Synthesis and characterization of a Ce3+ trivalent scheelite-type double tungstate by solid state method

The trivalent cerium silver tungstate, AgCe(WO4)2, with scheelite-like structure has been synthesized by solid-state method despite the relatively high instability of the trivalent Ce ion. This behavior could be explained by the redox properties of Ag2O in the solid state reaction at high temperature in air, which stabilizes the trivalent valence state. X-ray diffraction analysis was carried out and the refinement was performed in the tetragonal S.G. I 41/a (No. 88). Initially differential thermal analysis (DTA) and thermal gravimetric (TG) were used to analyze the reaction process and chemical mechanism. High temperature X-ray diffraction was introduced in to investigate the thermal stability and phase transition properties. It is found that AgCe(WO4)2 can be decomposed into Ag2W2O7 and Ce2(WO4)3 at temperature range of 500 °C – 700 °C. No phase transition was observed up to 900 °C from room temperature. The results of magnetic susceptibility measurement give confirmed evidence that the trivalent cerium cation existed in the compounds Ag(1+x) Ce(1-x)(WO4)2 (x from 0 to 1/3), and no transition from trivalent Ce3+ cation to tetravalent Ce4+ cation was observed even with decreasing cerium concentration. The fluorescence properties of Eu3+ and Tb3+ doped AgCe(WO4)2 were investigated. It is found that Tb3+ is qualified as a local structure probe rather than Eu3+ in the AgCe(WO4)2 compound considering the quenching mechanism which probably due to the metal to metal charge transfer between Ce3+/W6+.

Unraveling the Key Features of the Reactive State of Decatungstate Anion in Hydrogen Atom Transfer (HAT) Photocatalysis

The decatungstate anion [W10O32]4– is a widely used photocatalyst for promoting hydrogen atom transfer (HAT) reactions. The mechanism implicated in the activation of organic substrates, however, still needs to be clarified and has been claimed to involve an unknown relaxed excited state of triplet multiplicity, tagged wO. A subpicosecond investigation allowed us to follow early events leading to the chemically reactive species. A hot singlet excited state (S1HOT) has been individuated through pump–probe experiments, yielding S1 by ultrafast decay (<1 ps). The reactive species wO arises from S1 in competition with decay to S0 (efficiency ca. 0.5) and has been detected spectroscopically by flash photolysis experiments, with peculiar absorption bands in the near-UV (370 nm) and visible (600–800 nm) regions. TD-DFT calculations demonstrated that excitation to S1 occurs through a ligand to metal charge transfer (LMCT) transition, involving a displacement of electron density from dicoordinated (bridging) oxygen...

Cd2+ and Pb2+ complexation by glutathione and the phytochelatins

Phytochelatins or PCn, (γGlu-Cys)n-Gly, and their glutathione (GSH) precursor are thiol-rich peptides that play an important role in heavy metal detoxification in plants and microorganisms. Complex formation between Cd2+ and Pb2+ and GSH or PCn (n = 2, 4 and 6) are investigated by microcalorimetry, absorption spectrophotometry and T-jump kinetics. Complex formation with Pb2+ or Cd2+ is exothermic, and induces ligand metal charge transfer bands in UV absorption spectral range, which implies the formation of a coordination bond between the metal and the thiol groups of the phytochelatins. Absorption spectra and microcalorimetry experiments allow the determination of the affinity constants and the stoichiometry of the complexes. We show that the three PCn interact with Pb2+ to form the 1:1 and 2:1 M:L complexes, with similar affinity constants (log K11Pb∼4.6, log K21Pb∼11.4). These affinities are independent of the number of thiols and are, moreover, lower than those determined for complex formation with Cd2+. On the other hand, with Cd2+, PC2-Cd, PC2-Cd2, (PC2)3-Cd2, PC4-Cd, PC4-Cd2, PC6-Cd, (PC6)2-Cd3 and PC6-Cd3 complexes are detected. Furthermore, for PC4-Cd, the 1:1 complex is the most stable: affinity constant (log K11Cd∼7.5). Kinetic studies indicate that complex formation between Cd2+ and GSH occurs in the ms range; direct rate constant kobs = (6.8 ± 0.3) 106 M−1 s−1 and reverse rate constant k−obs = 340 ± 210 s−1. Thus, when encapsulated in a silica matrix, PCn can be good candidates for heavy metal detection.

Systematic First-Principles Calculations of Charge Transfer Transitions of Transition Metal Ions in α-Al2O3 and Optimization of the Computational Condition

[Introduction] Persistent phosphors are materials showing continuous luminescence for long durations from several minutes to hours after optical excitation has ceased. The materials have carrier traps that play the most important role in the persistent luminescence process. Ueda et al. of Kyoto University developed a blue-light-induced persistent luminescence material Ce3+ -Cr3+:Y3Al2Ga3O12 by doping Cr into Ce3+:Y3Al2Ga3O12, where the 3d orbitals of Cr3+ work as trap centers to capture electrons[1]. The persistent luminescence properties are dominated by the position of the energy levels of the trap centers in the band gap and therefore can be controlled by changing the doped transition metal (TM) ion. Generally, it is difficult to calculate the band gap energy by first-principles calculations based on the cluster method due to the poor reproduction of the conduction band. Accordingly, the transition energy from the impurity level to the conduction band cannot be calculated directly. However, the position of the impurity level within the band gap can be estimated by calculating the charge transfer transition energy from the valence band (Ligand to Metal Charge Transfer: LMCT). In this study, in order to obtain the LMCT energy for various trivalent TM ions in α-Al2O3, we performed first-principles calculations using the DVME method[2]based on configuration interaction (CI) method and constructed the theoretical energy diagram of the transition metal 3d levels within the band gap. By comparing the theoretical diagram with the available experimental LMCT energies in detail, the optimized computational condition was also proposed. [Computational Method] We constructed a 7-atom cluster with C3 symmetry consisting of the central aluminum ion and the first-neighbor oxygen ions from the crystal data of α-Al2O3 [3]and then we substituted various trivalent TM (Sc, Ti, V, Cr, Mn, Fe, Co) ions for the central aluminum ion. The effective Madelung potential was considered by setting point charges on the atomic sites around the cluster. In order to improve the computational accuracy, the lattice relaxation (LR) caused by the substitution of TM for aluminum was considered by estimating the change of the bond length based on the Shannon’s crystal radii, and the configuration dependent correction (CDC) was also considered. The LMCT energy was calculated as the transition energy from the top of the valence band corresponding to the highest one of the MOs mainly consisting of oxygen 2p orbital to the MO mainly consisting of TM 3d orbital based on the MO calculation using the DV-Xα method and the CI calculation using the DVME method. [Result] The theoretical LMCT energies calculated with LR and CDC are shown as the diagram in Fig. 1 together with the diagram for the experimental values[4-6]. The figure shows that the experimental trend was successfully reproduced by first-principles calculations. The remaining underestimation for Sc and Ti is probably due to the overestimation of the lattice relaxation arising from the simple approximation. On the other hand, the overestimation for Fe is probably due to the insufficient consideration of electron correlation. [References] [1] J. Ueda, et al,. Appl. Phys. Lett. 104, 101904, (2014). [2] K. Ogasawara, et al., Phys. Rev. B, 64, 115413, (2001). [3] E. N. Maslen, et al., Acta Crystallogr. Sect. B, 49, 973-980 (1993). [4] B. R. Namozov, et al., Physics of the Solid State, 40, 599-600 (1998). [5] H. H. Tippins, Phys. Rev. B, 1, 126-135 (1970). [6] D. S. McClure, J. Phys. Chem., 36, 2757-2779 (1962). Figure 1

Conductivity in Cuprates Arises from Two Different Sources: One-Electron Exchange and Disproportionation

Simulation of the resistivity in the normal state of doped La2−xSrxCuO4 has been performed using a hopping model based on Marcus theory. The results are in substantial agreement with experimental results. At oxidative doping, Cu(III) sites are formed and electron mobility possible due to hopping: Cu(III)Cu(II) → Cu(II)Cu(III) (one-electron exchange). In the underdoped, non-metallic region, the resistivity (ρ) decreases from almost insulation at T = 0 to a minimum at about T = 100 K. ρ then increases more than linearly with T (∼T3/2) in the region 100 < T < 500 K. A photo-induced metal-metal (MM) charge transfer transition at 2 eV 2Cu(II) + h ν→ Cu(I) + Cu(III) is responsible for the strong absorption in the visible spectrum of La2CuO4. The down-shift of spectral density with doping (x) in La2−xSrxCuO4 depends on the appearance of Cu(III) sites which makes optical as well as thermal one-electron exchange transitions possible with lower energy. Disproportionation occurs spontaneously for x > 0.06, opening up for electron pair formation. Configuration interaction between two-electron states of low chemical potential, but strong vibrational coupling, gives rise to the superconductor and pseudogaps. Data from photo-induced conductivity and absorption spectra are used in the simulation, which gives results in good agreement with experiments. Possible explanations for Raman and MIR absorption suggest themselves.

Introducing saccharic acid as an efficient iron chelate to enhance photo-Fenton degradation of organic contaminants

The identification of iron chelates that can enhance photo-Fenton degradation is of great interest in the field of advanced oxidation process. Saccharic acid (SA) is a polyhydroxy carboxylic acid and completely non-toxic. Importantly, it can effectively bind Fe(III) as well as induce photoreduction of Fe(III). Despite having these interesting properties, the effect of SA on photo-Fenton degradation has not been studied. Herein, we demonstrate the first assessment of SA as an iron chelate in photo-Fenton process using methylene blue (MB) as a model organic contaminant. Our results demonstrate that SA has the ability to (i) enhance the photo-Fenton degradation of MB by about 11 times at pH 4.5 (ii) intensify photochemical reduction of Fe(III) to Fe(II) by about 17 times and (iii) accelerate the rate of consumption of H2O2 in photo-Fenton process by about 5 times (iv) increase the TOC reduction by about 2 times and (v) improve the photo-Fenton degradation of MB in the presence of a variety of common inorganic ions and organic matter. The influential properties of SA on photo-Fenton degradation is attributed to the efficient photochemical reduction of Fe(III) via LMCT (ligand to metal charge transfer reaction) to Fe(II), which then activated H2O2 to generate OH and accelerated photo-Fenton degradation efficiency. Moreover, the effect of operational parameters such as oxidant: contaminant (H2O2: MB) ratio, catalyst: contaminant (Fe(III)SA: MB) ratio, Fe(III): SA stoichiometry and pH on the degradation of MB by photo-Fenton in the presence of SA is demonstrated. Importantly, SA assisted photo-Fenton caused effective degradation of MB and 4-Chlorophenol under natural sunlight irradiation in natural water matrix. The findings strongly support SA as a deserving iron chelate to enhance photo-Fenton degradation.

UV light induces Ag nanoparticle formation: roles of natural organic matter, iron, and oxygen

Nanoparticles occurring in the environment originate either from engineered, synthetically produced nanoparticles, or from naturally produced nanoparticles. The latter can be formed in natural media by light-induced reduction of metal ions in presence of natural organic matter, such as humic substances occurring widely in waters, soils and sediments. There is actually few knowledge on the effect of sunlight and of the nature of organic matter on nanoparticle formation. Therefore, we studied here the photoreduction of silver(I) ion to silver nanoparticles with and without ferrous ion under oxic and anoxic conditions, using humic and fulvic acids as proxies of natural organic matter. UV light-induced formation of silver nanoparticles was monitored up to 60 min by measuring surface plasmon resonance in air-saturated mixture and nitrogen-saturated mixture of silver(I) ion–organic matter. Results show that the surface plasmon resonance intensity was about 2.5 times higher in the nitrogen-purged solution mixture than the air-saturated solution. This finding suggests the oxygen-containing species had no major role in forming silver nanoparticles. Therefore, photo-driven formation of silver nanoparticles most likely involved photoactivation of silver(I) ion and natural organic matter complexes. We observed also that both iron(II) and iron(III) ions highly modified the surface plasmon resonance spectra of the particles with broader features. Results also reveal that in the presence of humic acid, the intensity of the surface plasmon resonance peak decreased by at least 50 %, while almost no change in the intensity was seen when fulvic acid was used. Overall, our findings demonstrate that the ligand–metal charge transfer process, affected by the nature of organic matter, i.e., humic acid versus fulvic acid, was influenced by redox iron species.

Consequences of ET and MMCT on Luminescence of Ce(3+)-, Eu(3+)-, and Tb(3+)-doped LiYSiO4.

Ce(3+), Eu(3+), and Tb(3+) singly doped, Ce(3+)-Tb(3+), Tb(3+)-Eu(3+), and Ce(3+)-Eu(3+) doubly doped, as well as Ce(3+)-Tb(3+)-Eu(3+) triply doped LiYSiO4 phosphors were prepared by a high-temperature solid-state reaction technique. Rietveld refinement was performed to determine the structure of host compound. The cross-relaxation (CR) of Tb(3+) is quantitatively analyzed with the Inokuti-Hirayama model of energy transfer (ET), and the site occupancy is confirmed by emission spectra of Eu(3+). ET and metal-metal charge transfer (MMCT) are systematically investigated in Ce(3+)-Tb(3+), Tb(3+)-Eu(3+), and Ce(3+)-Eu(3+) doubly doped systems. The combined effects of ET and MMCT on luminescence and emission color of Ce(3+)-Tb(3+)-Eu(3+) triply doped samples are discussed in detail, showing that the photoluminescence emission is tunable in a large color gamut.

Optical Properties of Gold Nanoclusters Functionalized with a Small Organic Compound: Modeling by an Integrated Quantum-Classical Approach.

Motivated by the growing importance of organometallic nanostructured materials and nanoparticles as microscopic devices for diagnostic and sensing applications, and by the recent considerable development in the simulation of such materials, we here choose a prototype system - para-nitroaniline (pNA) on gold nanoparticles - to demonstrate effective strategies for designing metal nanoparticles with organic conjugates from fundamental principles. We investigated the motion, adsorption mode, and physical chemistry properties of gold-pNA particles, increasing in size, through classical molecular dynamics (MD) simulations in connection with quantum chemistry (QC) calculations. We apply the quantum mechanics-capacitance molecular mechanics method [Z. Rinkevicius et al. J. Chem. Theory Comput. 2014, 10, 989] for calculations of the properties of the conjugate nanoparticles, where time dependent density functional theory is used for the QM part and a capacitance-polarizability parametrization of the MM part, where induced dipoles and charges by metallic charge transfer are considered. Dispersion and short-range repulsion forces are included as well. The scheme is applied to one- and two-photon absorption of gold-pNA clusters increasing in size toward the nanometer scale. Charge imaging of the surface introduces red-shifts both because of altered excitation energy dependence and variation of the relative intensity of the inherent states making up for the total band profile. For the smaller nanoparticles the difference in the crystal facets are important for the spectral outcome which is also influenced by the surrounding MM environment.

Optical Determination of Electron Transfer Dynamics and Kinetics for Asymmetrical [Mo2]–ph–[Mo2] Systems

We report the study, in terms of electronic coupling (EC) and electron transfer (ET), on three asymmetrical Mo2 dimers [Mo2(DAniF)3]2[μ-(NH)OCC6H4CO2] ([NO–ph–OO]) (DAniF = N,N′-di(p-anisyl)formamidinate), [Mo2(DAniF)3]2[μ-(NH)2CC6H4CO2] ([NN–ph–OO]), and [Mo2(DAniF)3]2[μ-(NH)2CC6H4C(NH)O] ([NN–ph–NO]), which are closely related to the three symmetrical analogues [OO–ph–OO], [NO–ph–NO], and [NN–ph–NN] reported earlier. The mixed-valence (MV) complexes [NO–ph–OO]+, [NN–ph–OO]+, and [NN–ph–NO]+ exhibit metal to ligand and ligand to metal charge transfer bands, along with an intervalence (IV) transition absorption in the Near-IR region. The free energy change (ΔG°) for ET is determined by comparing the redox potential splitting (ΔE1/2) and IV transition energy (EIT) with the data for the symmetrical species. The reorganization energy (λ) is estimated from the Hush model (Δν1/2 = [16ln(2)λRT]1/2). Significantly, electrochemical and optical analyses verify EIT = ΔG° + λ, the core energetic relationship underlying the semiclassical theories. With the electronic coupling parameters calculated from the method suggested by Creutz, Newton and Sutin (HMM′ = ∼ 500 cm–1), the adiabatic ET rate constants ket (f) are determined to be ∼1010 s–1 for [NO–ph–OO]+ and [NN–ph–NO]+, smaller than ket (r) for the backward reaction and ket for the symmetrical analogues by 1 order of magnitude, and ∼109 s–1 for [NN–ph–OO]+. This work illustrates that the redox asymmetry in D–B–A systems controls the ET rate and direction.

A computational study of magnetic exchange interactions of 3d and 4f electrons in Ti-Ce co-doped AlN

To investigate the nature of 3d-4f exchange interactions in III-Nitride semiconductors, Ti-Ce co-doped AlN were studied using first principles calculations. The calculations were performed using supercell approach with varying dopant concentration and different inter-dopant separation. The configuration with dopant located as nearest neighbor distance and diluted concentration of 3.125% was found most stable. The results exhibited prominent evidence of 3d-4f-5d strong hybridization suggesting 3d-4f direct exchange interactions which may play valuable role to exploit the system as high Curie temperature ferromagnetic semiconductors for use in spintronics. Moreover, metal to metal charge transfer was also observed in the materials which may be exploited for their use in electrochemical applications. The 4f-5d and 3d-5d hybridizations were observed that predicts excellent luminescence phenomena in the materials. The presence of impurity related deep intermediate bands suggest applications of the materials in opto-electronic and spintronics devices.

Photoluminescence, Judd–Ofelt analysis and photometric characterization of Eu3+ activated Ca0.5Gd(WO4)2 red phosphor

The red emitting Ca0.5Gd(WO4)2:Eu3+ was synthesized by a solid-state reaction method. X-ray diffraction patterns were used to characterize crystal structure as well as phase purity. The results suggest that the as synthesized powder phosphor possess scheelite crystal structure with tetragonal symmetry along with the space group of I41/a. SEM studies reveal that the as synthesized sample show polyhedral morphology with particle size of 5.5 µm. Photoluminescence excitation spectrum depicts that a broad band (from 200 to 300 nm) centered at 242 nm is attributed to the ligand to metal charge transfer transition of WO42− and three intense with sharp absorption bands (observed at 394, 464 and 535 nm) are designated as f–f electronic transitions of Eu3+. Photoluminescence emission studies indicate that, under 394 nm UV excitation, a hypersensitive red emission was observed at 617 nm due to the transition from upper 5D0 level to the 7F2 lower level of Eu3+ ion. The spectroscopic behaviour of the as synthesized phosphor Ca0.5Gd(WO4)2:Eu3+ was determined using Judd–Ofelt theory. The CIE color coordinates, colour correlated temperature and luminous efficacies of radiation were estimated. The as obtained results indicating that the Ca0.5Gd(WO4)2:Eu3+ red phosphor is most suitable for solid state lighting applications.

5,6-Dihydroxyindole-2-carboxylic Acid–TiO2 Charge Transfer Complexes in the Radical Polymerization of Melanogenic Precursor(s)

A combination of biomedical and technological applications is generating, over the past decades, the well-established interest toward melanins and melanogenesis. Several compounds have been explored to promote/catalyze oxidative polymerization of melanogenic precursors, such as 5,6-dihydroxyindole-2-carboxylic acid (DHICA), to melanin-like biopolymers in vitro. TiO2 has shown a photocatalytic activity driving DHICA polymerization and leading to the formation of melanin–TiO2 hybrid nanostructures with unique biocide behavior even under visible light. However, the mechanism of melanin formation in those hybrids is not yet well understood although a ligand to metal charge transfer (LMCT) process involving DHICA and Ti4+ ions was hypothesized. Here, we focus on melanin formation and apply a complementary analysis, by using photoluminescence (PL), UV–vis, electron paramagnetic resonance (EPR), and nuclear magnetic resonance (NMR) spectroscopy to reveal the mechanism of DHICA polymerization in the presence of a...

Interactions between metal cations with H2 in the M+- H2 complexes: Performance of DFT and DFT-D methods

The interactions between metal cations (Ni+, Cu+, Zn+) and H2 molecule have been investigated in detail using dispersion-corrected and -uncorrected double hybrid density functional (DHDF), gradient corrected density functional, ordinary density functional and CCSD(T) methods in conjunction with the correlation consistent triple- ζ quality basis sets. Structural properties, depth of the potential well and dissociation energies are calculated using DFT, DFT-D and CCSD(T) methods and are compared with experimental results. A comparative analysis has been made among DFT, DFT-D and CCSD(T) methods with respect to experiments. The energy components of the interaction energy have been estimated by the symmetry-adapted perturbation theory (SAPT) to analyze the effect of various components on the interaction of the complexes. The dispersion-corrected DHDF, mPW2PLYP-D method shows the best agreement with the experimental values. An NBO analysis has been performed to understand the orbital participation in metal ligand interaction and charge transfer process in these complexes.

Bimetallic Au2Cu6 Nanoclusters: Strong Luminescence Induced by the Aggregation of Copper(I) Complexes with Gold(0) Species

AbstractThe concept of aggregation‐induced emission (AIE) has been exploited to render non‐luminescent CuISR complexes strongly luminescent. The CuISR complexes underwent controlled aggregation with Au0. Unlike previous AIE methods, our strategy does not require insoluble solutions or cations. X‐ray crystallography validated the structure of this highly fluorescent nanocluster: Six thiolated Cu atoms are aggregated by two Au atoms (Au2Cu6 nanoclusters). The quantum yield of this nanocluster is 11.7 %. DFT calculations imply that the fluorescence originates from ligand (aryl groups on the phosphine) to metal (CuI) charge transfer (LMCT). Furthermore, the aggregation is affected by the restriction of intramolecular rotation (RIR), and the high rigidity of the outer ligands enhances the fluorescence of the Au2Cu6 nanoclusters. This study thus presents a novel strategy for enhancing the luminescence of metal nanoclusters (by the aggregation of active metal complexes with inert metal atoms), and also provides fundamental insights into the controllable synthesis of highly luminescent metal nanoclusters.