Metal Charge Transfer Research Articles

Reversal of charge transfer direction at gold/copper phthalocyanine film interface on post deposition annealing: A vibrational spectroscopic study

Charge transfer interaction at the gold (Au)/copper phthalocyanine (CuPc) interface, with Au on CuPc film, was investigated using vibrational techniques - Fourier Transform Infra Red and Raman spectroscopy, in combination with X- ray photoelectron spectroscopy. The charge transfer direction at this interface was found to be changing after annealing of the CuPc film, as compared to that before annealing. Molecule to metal charge transfer at the Au/CuPc interface observed for the as deposited film was found to be reversing to metal to molecule charge transfer for the annealed film. This reversal of charge transfer direction in the latter was attributed to the modified electronic structure/work function of the CuPc film and the varying orientation of CuPc molecules at the interface, brought about by the increased surface roughness, change in morphology, etc. The reversal in charge transfer direction was suggested to be supporting the reduction in parasitic contact resistance at the Au/CuPc interface for a top contact OFET with the annealed CuPc film, as compared to that with the as deposited film. This study demonstrates the influence of morphology of the organic semiconductor film on the charge transfer behaviour at the metal/organic semiconductor interface.

Composition-Thermometric Properties Correlations in Homodinuclear Eu3+ Luminescent Complexes.

A family of homodinuclear Ln3+ (Ln3+ = Gd3+, Eu3+) luminescent complexes with the general formula [Ln2(β-diketonato)6(N-oxide)y] has been developed to study the effect of the β-diketonato and N-oxide ligands on their thermometric properties. The investigated complexes are [Ln2(tta)6(pyrzMO)2] (Ln = Eu (1·C7H8), Gd (5)), [Ln2(dbm)6(pyrzMO)2] (Ln = Eu (2), Gd (6)), [Ln2(bta)6(pyrzMO)2] (Ln = Eu (3), Gd (7)), [Ln2(hfac)6(pyrzMO)3] (Ln = Eu (4), Gd (8)) (pyrzMO = pyrazine N-oxide, Htta = thenoyltrifluoroacetone, Hdbm = dibenzoylmethane, Hbta = benzoyltrifluoroacetone, Hhfac = hexafluoroacetylacetone, C7H8 = toluene), and their 4,4′-bipyridine N-oxide (bipyMO) analogues. Europium complexes emit a bright red light under UV radiation at room temperature, whose intensity displays a strong temperature (T) dependence between 223 and 373 K. This remarkable variation is exploited to develop a series of luminescent thermometers by using the integrated intensity of the 5D0 → 7F2 europium transition as the thermometric parameter (Δ). The effect of different β-diketonato and N-oxide ligands is investigated with particular regard to the shape of thermometer calibration (Δ vs T) and relative thermal sensitivity curves: i.e.. the change in Δ per degree of temperature variation usually indicated as Sr (% K–1). The thermometric properties are determined by the presence of two nonradiative deactivation channels, back energy transfer (BEnT) from Eu3+ to the ligand triplet levels and ligand to metal charge transfer (LMCT). In the complexes bearing tta and dbm ligands, whose triplet energy is ca. 20000 cm–1, both deactivation channels are active in the same temperature range, and both contribute to determine the thermometric properties. Conversely, with bta and hfac ligands the response of the europium luminescence to temperature variation is ruled by LMCT channels since the high triplet energy (>21400 cm–1) makes BEnT ineffective in the investigated temperature range.

Photo Augmented Copper-based Fenton Disinfection under Visible LED Light and Natural Sunlight Irradiation

Copper-based Fenton disinfection system (Cu(II)/H2O2) is an emerging advanced oxidation process (AOP). Previous works have used reducing agents and organic ligands to improve the disinfection efficiency of Cu(II)/H2O2 system. Here, we report visible light/Cu(II)/H2O2 system showed enhanced disinfection compared to Cu(II)/H2O2 system, without the need of reducing chemical agent or organic ligand. Energy-efficient LED array was used as a visible light source in the visible light/Cu(II)/H2O2 system. Under the optimized condition, pseudo-first-order inactivation rate constant (kobs) of E. coli by visible light/Cu(II)/H2O2 (0.613 ± 0.005 min−1) was about ~8 times greater than Cu(II)/H2O2 (0.08 ± 0.011 min−1). Scanning electron microscopy and Baclight Live/Dead assay proved enhanced cell membrane damage by visible light/Cu (II)/H2O2 in comparison with Cu(II)/H2O2. Based on the bovine serum albumin (BSA) degradation and OH˙ radical measurement by visible light/Cu(II)/H2O2, a ligand to metal charge transfer (LMCT) mechanism by Cu(II)–bacterial complex is proposed for enhanced disinfection. Electrical energy efficiency (E E,1) for a log reduction of E. coli and the total treatment cost of visible light/Cu(II)/H2O2 was determined to be 32.64 KWh/m3 and 350 ₹/m3 (3.9 €/m3 or 4.74 $/m3), respectively, indicating its cost-effectiveness. Disinfection efficiency by sunlight/Cu(II)/H2O2 system (solar irradiance; 746 ± 138 W/m2) was almost comparable to LED-based visible light/Cu(II)/H2O2 system, with total treatment cost estimated to be 80 ₹/m3 (0.9 €/m3 or 1.1 $/m3).

Removal of toxic heavy metal ions from waste water using superchalcogens: A theoretical study

One of the most exciting events in chemistry is the stable assemblies of atoms, denoted by superatoms, that could mimic the behaviors of elements in the periodic table. For the first time by Jena et al., a novel type of di-anions superchalcogens (BeAl122− and TiAu122-) has been introduced based on the various electron-counting rules. Inspired by the fascinating finding of these superatoms and guided by density functional theory calculations, we propose a novel and efficient strategy to capture pollutants from waste water via adsorbing the toxic heavy metal cations (Cd2+, Hg2+, and Pb2+) by the BeAl122− and TiAu122− superchalcogens. Our results reveal that the BeAl122− and TiAu122− superchalcogens were powerful to adsorb the Pb2+, Hg2+, and Cd2+ cations in the aqueous solution. Furthermore, by investigating the hydrated cations, the adsorption of hydrated [Pb(H2O)4]2+ on the BeAl122− and TiAu122− superatoms was found thermodynamically more favorable than the [Cd(H2O)4]2+ and [Hg(H2O)4]2+. Our calculations also showed that the adsorbing heavy metal cations can considerably narrow the wide HOMO-LUMO gap and remarkably enhance the first hyperpolarizability of the pristine BeAl122− and TiAu122− superchalcogens, due to electron transfer in this type of superatoms. Moreover, the results highlight the systems with higher electron transport rates, show the larger first hyperpolarizability as well as the higher nonlinear optical response. Time-dependent density functional calculations also revealed “ligand to metal charge transfer” vertical excitations for the cation/superchalcogen systems. However, these theoretical findings might be helpful for experimental scientists toward designing high-efficient adsorbents based on superatoms for eliminating water pollutants.

Prediction of NLO response of substituted organoimido hexamolybedate: First theoretical framework based on p-anisidine adduct [Mo6O18(p-MeOC6H4N)]2-

The second-order nonlinear optical (NLO) responses and dipole polarizabilities of p-anisidine adduct (imido derivative of hexamolybdates/polyoxometalates/POMs/Cluster) are studied by means of time dependent density functional (TDDFT) calculations. A substantial molecular second-order NLO response has been noticed in these organic-inorganic hybrid compounds, particularly [Mo6O17 cis-(p-MeOC6H4N)2]2− (system 2) and [Mo6O18 p-MeOC6H4N]2- (system 1) having static second-order polarizability (βvec) calculated to be 1949.60 au and 1565.10 au respectively. Both p-anisidine and cis-(p-anisidine) are found to be preferred choice over the trans-(p-anisidine) adduct. There is a fair probability for these systems to be selected as efficient second-order nonlinear optical materials. The movement of charge transfer from p-anisidine to hexamolybdate cluster (D–A) along the y-axis suggests molybdenum cluster acts as an acceptor (A) whereas p-anisidine working as a donor (D) in all the studied systems which is responsible for NLO response in such adducts. An incremental increase in the computed βvec values were evaluated by incorporation of an electron donor (Metalloporphyrin) instead of p-anisidine. Furthermore, substitution of Fe over Zn in Metalloporphyrin cage has enhanced the optical nonlinearity. This research effort offers a significant understanding into metal (Fe/Zn) to metal (Mo) charge transfer through imido-linkage in hexamolybdates, which has been found to be an efficient mode to enhance NLO response as a prime example in modulation of optoelectronics.

Microwave-assisted in-situ incorporation of nanostructured HyWO3-x on cotton cellulose for enhanced ultraviolet shielding applications

Nanostructured materials modified cotton cellulose could be a versatile and cost-effective solution for developing wide range of protective fabrics. In this background, cotton cellulose was surface modified with hydrated form of non-stoichiometric tungsten oxide (HyWO3-x) using microwave reduction technique for the development of UV radiation blocking and thermo-chromic fabrics. Herein, the surface modification and characterization of cotton cellulose having ligand to metal charge transfer (LMCT) transition via reduction process with enhanced UV blocking features are presented. X-ray diffraction patterns confirmed the poly-crystalline and amorphous nature of unmodified and surface modified cotton fabrics. Scanning electron micrographs revealed the growth of nanostructured HyWO3-x on cotton cellulose and surface analysis showed the existence of tungsten, carbon, oxygen elements. Differential scanning calorimetry of treated fabric exhibited a change of exothermic behavior from endothermic at the characteristic onset temperature. Thermogravimetric analysis revealed the least weight loss up to 600°C of the surface treated cotton cellulose. Further, Ultraviolet Protection Factor (UPF) of the modified fabric was measured using an in-vitro method following the AATCC 183:2004 standard employing UV transmittance analyzer. The UPF was estimated to be 2000, which is excellent for protective clothing applications according to UPF standard for fabrics. Also, the ligand to metal charge transfer characteristics of WO3-x modified cotton cellulose revealed the selective transition towards microwave irradiation at different reduction power.

Visible‐Light‐Induced Vicinal Dichlorination of Alkenes through LMCT Excitation of CuCl2

AbstractThis work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl2 in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2‐dichloride compounds using an inexpensive, low‐molecular‐weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C−Cl bonds in this synthetic process.

Visible-Light-Induced Vicinal Dichlorination of Alkenes through LMCT Excitation of CuCl2.

This work demonstrates photoredox vicinal dichlorination of alkenes, based on the homolysis of CuCl2 in response to irradiation with visible light. This catalysis proceeds via a ligand to metal charge transfer process and provides an exciting opportunity for the synthesis of 1,2-dichloride compounds using an inexpensive, low-molecular-weight chlorine source. This new process exhibits a wide substrate scope, excellent functional group tolerance, extraordinarily mild conditions and does not require external ligands. Mechanistic studies show that the ready formation of chlorine atom radicals is responsible for the facile formation of C-Cl bonds in this synthetic process.

Large magnetodielectric effect based on spin-dependent charge transfer in metal–insulator type Co-(BaF2) nanogranular films

Cobalt-metal-fluoride nanogranular films exhibit high electrical resistivity (ρ) and high permittivity (ɛ′) as well as high magnetic moments, making them potentially suitable for applications in low power magnetoelectronic devices at a high-frequency range. Here, we present the DC/AC magnetoelectric effect of high-ρ Cox-(BaF2)1 − x nanogranular films that are constituted of Co nanogranules of about 2 nm in diameter in an insulating BaF2 crystal. Under the application of magnetic field (H), we observed the ρ variations (Δρ/ρ0) of 2.0%–5.9% for x ranging 0.19–0.54 and the ɛ′ variations (Δɛ/ε0′) of 0.7%–6.0% for x ranging 0.19–0.42, respectively. These magnetically controllable ρ and ɛ′ are realized based on the spin-dependent quantum-mechanical charge transfer. The Cox-(BaF2)1 − x film for x = 0.42 possesses high ρ, while remaining in a notably high Δɛ/ε0′ of 6% at a megahertz frequency range. This study demonstrates a candidate of high-resistive magnetoelectric nanogranular films, which may bring prosperous applications in high-frequency magnetoelectric devices with low power consumption.

A novel fluorescent chemosensor for Cu2+ ion based on a new hexadentate ligand receptor: X-ray single crystal of the perchlorate salt of the ligand, ion selectivity assays and TD-DFT study

New hexadentate chelates, H2L1 and L1, were synthesized. The Schiff base imine ligand, L1, was prepared by reaction of 2,2′-[ethane-1,2-diylbis(oxy)]dibenzaldehyde and propanolamine, and characterized by infrared (IR), 1H NMR and 13C NMR spectroscopies. The amine ligand, H2L1, was prepared in the form of perchlorate salt ([H4L1](ClO4)2,) by reduction of L1 with NaBH4, and was characterized by IR (in KBr pellet), 1H NMR, 13C NMR and 2D NMR correlation spectroscopy (COSY) (in solution). The X-ray crystal structure of [H4L1](ClO4)2 was also determined and discussed. Fluorescence studies showed that H2L1 is a highly selective novel fluorescence chemosensor for the Cu2+ cation. The sensor shows selectivity for Cu2+ over 12 other metal cations. In presence of Cu2+ (5 equivalents in the μM range) the fluorescence emission of the sensor, at 309 nm, is quenched by more than 98%. TD-DFT calculations show that ligand to metal charge transfer transitions in the complex formed between Cu2+ and the amine ligand contribute to the quenching of the fluorescence. An explanation based on TD-DFT results is also proposed for the weak fluorescence quenching in the presence of Zn2+.

Triphenyl-imidazole based reversible coloro/fluorimetric sensing and electrochemical removal of Cu2+ ions using capacitive deionization and molecular logic gates

A simple hydroxyl-substituted triphenyl-imidazole based receptor (HTPI) which selectively detects Cu2+ ion by colorimetric and fluorimetric methods was developed. HTPI detects the Cu2+ ions with the absorption enhancement and fluorescence quenching by the possible ligand to metal charge transfer (LMCT) and the chelation-enhanced quenching (CHEQ) approaches, respectively. HTPI showed high selectivity and sensitivity for Cu2+ ions detection over other interfering and competing metal ions. Interestingly, HTPI detects Cu2+ ion (LOD) at nanomolar concentrations (19×10-9M (UV-vis) & 27×10-9M (fluorescence), respectively), which is lower than the permissible level of Cu2+ ion reported by World Health Organization (WHO). Furthermore, HTPI was applied to the molecular logic gate function by using chemical inputs, and Cu2+ ion was potentially removed (95%) via Capacitive Deionization technique.

Synthesis, characterization and density functional theory of copper(II) complex and cobalt(II) coordination polymer for detection of nitroaromatic explosives

In recent years there has been a significant interest to design luminescent materials to detect explosives with a great degree of selectivity, sensitivity, and fast response time. Two new luminescent compounds, [Cu(Biphen)(Meim)(H2O)] 1 and [Co(BDC)(Meim)2]n2 (where HBiphen = biphenyl-4-carboxylic acid, H2BDC = 1,4-benzenedicarboxylic acid and Meim = 1-methylimidazole) were synthesized under solvothermal and reflux conditions. The compounds were characterized by elemental analysis, FT-IR, thermogravimetric analysis, and electronic spectroscopy. Single Crystal X-ray Diffraction (SC-XRD) was used to determine their crystal structures. 1 crystallizes in the monoclinic space group I2/a, and the geometry around the metal center is square pyramidal connected by two (μ-N)2 of Meim and two (μ-O)2 of Biphen and a coordinated water molecule. 2 exhibits tetrahedral geometry connected by two (μ-N)2 of Meim and two (μ-O)2 halves of BDC in the triclinic space group P-1. Photophysical properties of the solid-state complexes were analyzed using fluorescence spectroscopy. 1 displayed high emissions at 430 nm (λex = 264 nm) and 2 at 384 nm (λex = 265 nm) which could be assigned to ligand to metal charge transfer (LMCT) due to the ligand's extended π-conjugation. Compounds 1 and 2 display selective nitroaromatic quenching response over other organic molecules having detection limits ranging between 1.66 ppm and 13.07 ppm, respectively. Density Functional Theory (DFT) revealed that potential interactions leading to the formation of adducts result from the transfer of electrons by hydrogen bonding and π-π stacking. Compound 2 was found to have greater ability to quench nitro analytes.

Light Runs Across Iron Catalysts in Organic Transformations.

Over the past decades, organometallic complexes with precious elements, such as ruthenium and iridium, are widely used as visible-light photoredox catalysts. Recently, more and more complexes based on earth-abundant and inexpensive elements have been used as sensitizers in photochemistry. Although the photoexcited state lifetimes of iron complexes are typically shorter than those of traditional photosensitizers, the utilization of iron catalysts in photochemistry has sprung up owing to their abundance, low price, nontoxicity, and novel properties, including exhibiting ligand to metal charge transfer states. This concept focuses on recent advances in light-driven iron catalysis in organic transformations, including iron/photoredox dual catalysis, light-induced iron photoredox catalysis and light-induced generation of active iron catalysts. The prospect for the future of this field is also discussed.

Continuous angular control over anisotropic photoemission from isotropic gold nanoshells.

A variety of applications rely on the efficient generation of hot carriers within metal nanoparticles and charge transfer to surrounding molecules or materials. The optimization of such processes requires a detailed understanding of excited carrier spatial, temporal, and momentum distributions, which also leads to opportunities for active optical control over hot carrier dynamics on nanometer and femtosecond scales. Such capabilities are emerging in nanoplasmonic systems and typically rely on tuning optical polarization and/or frequency to selectively excite one or more discrete hot spots defined by the particle geometry. Here, we introduce a unique case in which hot electron excitation and emission distributions can instead be continuously controlled via linear laser polarization in the azimuthal plane of a gold nanoshell supported on a substrate. In this configuration, it is the laser field that breaks the azimuthal symmetry of the supported nanoshell and determines the plasmonic field distribution. Using angle-resolved photoelectron velocity map imaging, we find that the hot electrons are predominantly emitted orthogonal to the nanoshell dipolar surface plasmon resonance axis defined by the laser polarization. Furthermore, such anisotropic emission is only observed for nanoshells, while solid gold nanospheres are found to be isotropic emitters. We show that all of these effects are recapitulated via simulation of the plasmonic electric field distributions within the nanoparticle volume and ballistic Monte Carlo modeling of the hot electron dynamics. These results demonstrate a highly predictive level of understanding of the underlying physics and possibilities for ultrafast spatiotemporal control over hot carrier dynamics.

One-Pot Synthesis of Thiol-Modified Liquid Crystals Conjugated Fluorescent Gold Nanoclusters.

Gold nanoclusters (AuNCs) and liquid crystals (LCs) have shown great potential in nanobiotechnology applications due to their unique optical and structural properties. Herein, the hardcore of the 4-cyano biphenyl group for commonly used LCs of 4-cyano-4′-pentylbiphenyl (5CB) was utilized to synthesize 4′-(2-mercaptoethyl)-(1,1′-biphenyl)-4-carbonitrile (TAT-12) based on Suzuki coupling and Appel reaction. The structural and optical properties of thiol-modified TAT-12 LCs were demonstrated by nuclear magnetic resonance (NMR) spectroscopy, ultraviolet-visible (UV-vis) spectroscopy and differential scanning calorimetry (DSC). By one-pot synthesis, thiol-modified TAT-12 LCs were used as the ligands to prepare fluorescent gold nanoclusters (AuNCs@TAT-12) according to the Au-S bond between AuNCs and TAT-12. The spectra of UV-vis absorption and X-ray photoelectron spectroscopy (XPS) of AuNCs@TAT-12 indicated that the core of gold of AuNCs@TAT-12 exhibited high gold oxidation states. The fluorescence of AuNCs@TAT-12 was observed with a maximum intensity at ~352 nm coming from TAT-12 on AuNCs@TAT-12 and the fluorescence quantum yield of AuNCs@TAT-12 was calculated to be 10.1%. Furthermore, the fluorescence with a maximum intensity at ~448 nm was attributed to a ligand–metal charge transfer between the ligands of TAT-12 LCs and the core of AuNCs. The image of transmission electron microscopy (TEM) further demonstrated an approximately spherical shape of AuNCs@TAT-12 with an average size of 2.3 nm. A combination of UV-vis absorption spectra, XPS spectra, fluorescence spectra and TEM image, fluorescent AuNCs@TAT-12 were successfully synthesized via one-pot synthesis. Our work provides a practical approach to the synthesis of LCs conjugated AuNCs for future applications in nanobiotechnology.

Improving Charge Transfer in Metal–Organic Frameworks through Open Site Functionalization and Porosity Selection for Li–S Batteries

The tunable nature of metal–organic frameworks (MOFs) enables versatility and precise control over structures and properties, making them feasible for potential applications including gas storage a...

Synthesis, Electrochemical, Thermodynamic, and Quantum Chemical Investigations of Amino Cadalene as a Corrosion Inhibitor for Stainless Steel Type 321 in Sulfuric Acid 1M

The corrosion of stainless steel is one of the major industries’ issues that gained wide interest among researchers. It became necessary to develop and apply eco-friendly approaches to corrosion control. This work explores the inhibitory effect of a newly synthesized amino cadalene (ACM) on the corrosion of stainless steel type 321 in sulfuric acid 1M. Particularly, the experimental study consisting of electrochemical and surface analyses was conducted in conjunction with a theoretical approach. The electrochemical results showed that ACM acted as a mixed-type corrosion inhibitor and the inhibition efficiency attained 91% at 10−3M. EIS measurements revealed that both metal charge transfer and diffusion processes are involved in the interfacial metal/solution reactions. The interfacial mechanism is thoroughly investigated; the physisorption of the protonated molecules was preceded by the formation of a negative layer due to adsorption of the solution anionic species. The experimental insights are corroborated with the quantum chemical calculations.

Dynamic dual spectral response on different cations by regulating PET and LMCT process of a simple luminescent sensor

A simple luminescent sensor BOPM-AB based on arylmaleimide (AM) with 4-methoxyphenyl and N, N-dimethylamino group was designed and synthesized. BOPM-AB exhibits dual spectra response of absorption and emission on Hg2+, Cu2+ and Fe3+. Interestingly, a dynamic response of BOPM-AB was observed upon the stimulus of Cu2+ or Fe3+. With the prolongation of interaction time, Cu2+ and Fe3+ make the emission of BOPM-AB become stronger and weaker, respectively. Titration experiments and DFT calculations demonstrate that the dynamic spectra response is closely related to two transfer process: photoinduced electron transfer (PET) from the N, N-dimethylamino to AM, and ligand metal charge transfer (LMCT) induced by metal ions. The unique of properties of BOPM-AB imposes it huge potential in the field of molecular operation. Combined with the factors of different loading amount, sequence of ions and coordinating time, two complex sequential logic systems (half-adder, and keypad lock) could be constructed based on BOPM-AB.

Enhanced multimodal behaviour of Tm3+/Yb3+ co-doped YTaO4 ceramic material through Bi3+ activation and sensitization: Application as a spectral converter

The multimodal [Upconversion (UC), Downshifting (DS) and Quantum cutting (QC)] behaviour of Tm3+/Yb3+ co-doped YTaO4 ceramic material is investigated extensively. The samples are prepared by solid-state reaction method at two different temperatures (at 1573 and 1723 K) and their structural and optical properties are compared with each other. The effect of synthesis temperature as well as doping, on crystal phase was analysed via X-ray diffraction measurements. Particles shape and size are investigated through scanning electron microscopy images. The structural behaviour is further verified through vibrational structural study of material via FTIR measurements. This shows similar structural changes as observed in XRD patterns of the samples prepared at two different temperatures. The optical band gap of YTaO4 is nearly 4.8 eV at both the temperatures. Intense blue (476 nm), red (648 nm) and NIR (802 nm) peaks are observed in UC emission spectra of Tm3+/Yb3+ co-doped YTaO4 ceramic on excitation with 980 nm. The blue UC emission is suitable for display devices. The UC emission intensity increases significantly when sample is prepared at higher temperature (1723 K). Addition of Bi3+ ion further enhances the overall UC emission intensity due to change in environment around the activator ion. On excitation with UV radiation (λExc = 284 nm), YTaO4: 1 Tm3+ produces intense DS emission at 454 nm (blue region) due to energy transfer from charge transfer band of [TaO4]3- to Tm3+ ion. The sample synthesized at 1723 K shows better DS emission. One interesting result is that addition of Bi3+ ion enhances the DS emission due to formation of metal-metal charge transfer band. We have also observed the quantum cutting phenomenon in which self-activated blue photon is converted into two or more NIR photons. The efficiency of quantum cutting emission increases significantly in presence of Bi3+ ion and shows strong, intense NIR emission through CET. Thus, the multimodal behaviour of Tm3+/Yb3+/Bi3+ doped YTaO4 makes them a suitable candidate for a spectral converter that can be used in display and solar cell devices.

Discrete Ti-O-Ti Complexes: Visible-Light-Activated, Homogeneous Alternative to TiO2 Photosensitisers.

A series of novel bimetallic TiIV amine bis(phenolate) complexes was synthesised and fully characterised. X‐ray crystallography studies revealed distorted octahedral geometries around the Ti centres with single or double oxo‐bridges connecting the two metals. These robust, air‐ and moisture‐stable complexes were employed as photosensitisers generating singlet oxygen following irradiation with visible light (420 nm) LED module in a commercial flow reactor. All five complexes showed high activity in the photo‐oxygenation of α‐terpinene and achieved complete conversion to ascaridole in four hours at ambient temperature. The excellent selectivity of these photosensitisers towards ascaridole (vs. transformation to p‐cymene) was demonstrated with control experiments using a traditional TiO2 catalyst. Further comparative studies employing the free pro‐ligands as well as a monometallic analogue highlighted the importance of the ‘TiO2‐like’ moiety in the polymetallic catalysts. Computational studies were used to determine the nature of the ligand to metal charge transfer (LMCT) states and singlet–triplet gaps for each complex, the calculated trends in the UV‐vis absorption spectra across the series agreed well with the experimental results.