Highly Efficient Blue Photoexcitation of Europium in a Bimetallic Pt–Eu Complex

Competing excitation paths in luminescent heterobimetallic Ln-Al complexes: Unraveling interactions via experimental and theoretical investigations

The interest for heterometallic lanthanide-d or-p metal (Ln-M) complexes is growing because of a potential cooperative or synergistic effect related to the proximity of two different metals in the same molecular architecture affording special tunable physical properties. To exploit the potentiality of Ln-M complexes, suitable synthetic approaches, and the in-depth understanding of the effect of each building block on their properties are mandatory. Here, we report the study on a family of heterometallic luminescent complexes [Ln(hfac)₃Al(L)₃], Ln= Eu³⁺ and Tb³⁺. Using different L ligands, we investigated the effect of the steric and electronic properties of the Al(L)₃ fragment, highlighting the general validity of the employed synthetic route. A marked difference in the light emission of [Eu(hfac)₃Al(L)₃] and [Tb(hfac)₃Al(L)₃] complexes has been observed. Thanks to photoluminescence experiments and Density Functional Theory calculations, Ln³⁺ emissions are explained with a model involving two non-interacting excitation paths through hfac or Al(L)₃ ligands.

Plant Photochemistry under Glass Coated with Upconversion Luminescent Film

It has been shown that the cultivation of plants under glass coated with nano-sized upconversion luminophores led to an increase in plant productivity and the acceleration of plant adaptation to ultraviolet radiation. In the present work, we examined the effect of upconversion nanopowders with the nominal composition Sr0.955Yb0.020Er0.025F2.045 on plant (Solanum lycopersicum) photochemistry. The composition, structure and size of nanoparticles were tested using X-ray pattern diffraction, scanning electron microscopy, and dynamic light scattering. Nanoparticles are capable of converting infrared radiation into red and green photons. Glasses coated with upconversion luminophores increase the intensity of photosynthetically active radiation and absorb the ultraviolet and far-red radiation. The chlorophyll a fluorescence method showed that plants growing under photoconversion and those growing under common film demonstrate different ability to utilize excitation energy via photosynthesis. It was shown that under ultraviolet and high light conditions, the efficiency of the photochemical reactions, the non-photochemical fluorescence quenching, and the electron transport remained relatively stable in plants growing under photoconversion film in contrast to plants growing under common film. Thus, cultivation of Solanum lycopersicum under photoconversion glasses led to the acceleration in plant growth due to greater efficiency of plant photochemistry under stress conditions.

Heterometal Grafted Metalla-ynes and Poly(metalla-ynes): A Review on Structure-Property Relationships and Applications

Metalla-ynes and poly(metalla-ynes) have emerged as unique molecular scaffolds with fascinating structural features and intriguing photo-luminescence (PL) properties. Their rigid-rod conducting backbone with tunable photo-physical properties has generated immense research interests for the design and development of application-oriented functional materials. Introducing a second d- or f-block metal fragment in the main-chain or side-chain of a metalla-yne and poly(metalla-yne) was found to further modulate the underlying features/properties. This review focuses on the photo-physical properties and opto-electronic (O-E) applications of heterometal grafted metalla-ynes and poly(metalla-ynes).

Utilization of a Pt(ii) di-yne chromophore incorporating a 2,2'-bipyridine-5,5'-diyl spacer as a chelate to synthesize a green and red emitting d-f-d heterotrinuclear complex

A new heterotrinuclear (d-f-d) complex [Eu(btfa)₃1c] (btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione and 1c = [(Ph)(Et₃P)₂Pt-C[triple bond, length as m-dash]C-R-C[triple bond, length as m-dash]C-Pt(Et₃P)₂(Ph)] (R = 2,2'-bipyridine-5,5'-diyl) has been synthesized by utilizing the N,N-donor sites of the organometallic chromophore. The complex was characterized by analytical and spectroscopic methods. Photophysical properties of the complex were analysed in detail using both steady-state and time-resolved emission and excitation spectroscopy. The optical absorption spectrum of the complex is dominated by the spin allowed π-π* transitions of the btfa and 1c units in the UV-visible region (200-418 nm) and thus is excitable over a wide range of wavelengths across the UV into the visible region of the electromagnetic spectrum. The complex displays typical red Eu(iii) emission when excited at 345 nm. However, it also shows green emission when excited at 464 nm and, thus could be an interesting candidate for full colour display applications. The change in the colour could be a result of the high value of the energy back-transfer rate (6.73 × 10⁵ s^-1) from the triplet state of the organometallic chromophore to the ⁵D₁ state of Eu(iii). Judd-Ofelt (J-O) intensity parameters (Ω₂ and Ω₄), radiative (A_R), non-radiative (A_R) decay rates and intrinsic quantum yield (Q) have been calculated.

Development and application of photoconversion fluoropolymer films for greenhouses located at high or polar latitudes

To convert and store energy in the process of photosynthesis, plants primarily use quanta of the red and blue parts of the spectrum. At high latitudes, the average daily intensity of red and blue parts of the spectrum is not very high; for many crops cultivated under greenhouse conditions, it reaches the sufficient level only on clear summer days. The problem of insufficient illumination in greenhouses is usually solved with artificial light sources. This article describes a technology for the manufacture of photoconversion fluoropolymer films for greenhouses. The fluoropolymer films described in the paper make use of original gold nanoparticles and nanoparticles with fluorescence in the blue or red region of the spectrum. In the polymer film, nanoparticles aggregate in the form of "beads", which enhances the field of the optical wave. The film photoconverts UV and violet light into blue and red light. Gold nanoparticles also partially convert energy in the green region of the spectrum (not used by plants) into heat, which is also important for agriculture at high latitudes. In addition, impregnation of gold nanoparticles into fluoropolymer significantly increases the lifetime of the film. The films described in the paper can significantly increase the productivity of greenhouses located at high latitudes. Plants cultivated under the films have more chlorophyll and a higher intensity of photosynthesis - although their system of distance stress signals is, to a certain degree, suppressed.

White light emission from a green cyclometalated platinum(ii) terpyridylphenylacetylide upon titration with Zn(ii) and Eu(iii )

The cyclometalated Pt(ii) acetylide derivative with a 1,3-bis(N-octyl-benzimidazol-2-yl)benzene (N^C^N) ligand and a free terpyridine (TPY) receptor has been successfully synthesized and characterized. X-ray crystallography shows its inefficient conjugation degree between the [(N^C^N)Pt] and TPY planes. This bifunctional complex shows an enhanced 1MLCT/LLCT absorption band (ε = 3.30 × 104 dm3 mol-1 cm-1) centered at λmax = 365 nm, and the well-resolved vibronic-structured 3MLCT/LLCT emission bands (Φ = 0.08, τ = 3.43 μs) in the range of ca. 475-700 nm. Consecutive titrations show that added Zn2+ and Eu(HFA)3 bond to its free TPY receptor with 1 : 2 and 1 : 1 stoichiometry to form the heterotrinuclear Pt-Zn-Pt (Ka = 3.48 × 104 mol-1 dm3) and heterodinuclear Pt-Eu (Ka = 1.73 × 104 mol-1 dm3) complexes, respectively. A sensitizing effect of Zn2+ on the TPY unit, and the incomplete d → f energy transfer from the [(N^C^N)Pt(ii)] antenna donor to the Eu(iii) center with maximum efficiency of 51.8% are observed. Using an in situ mixed titration strategy, the R/G/B emission triads consisted of red [(TPY)Eu(HFA)3] and green [(N^C^N)Pt(ii)] dual phosphorescence and blue [(TPY)Zn(TPY)] fluorescence, which can be well balanced to realize the white-light-emission with CIE coordinates (x = 0.36, y = 0.36) by precisely controlling the molar ratio (9 : 1 : 2) of the parent complexes, Eu(HFA)3 and Zn(ClO4)2.

Quantification of energy transfer in bimetallic Pt(ii)-Ln(iii) complexes featuring an N^C^N-cyclometallating ligand

Cyclometallated Pt(ii) complexes with arylpolypyridyl ligands have impressive photophysical properties (high quantum yields, long lifetimes and tuneable emission) which can be readily tuned by modification of the organic ligand. Despite this, few examples of cyclometallated Pt(ii) complexes as sensitisers for Ln(iii) emission have been reported. Herein, we report the photophysical properties for a series of bimetallic complexes incorporating an N^C^N-coordinated Pt(ii) bearing an alkynyl terpyridine as a metalloligand for a Ln(iii) ion (where Ln = Nd, Gd, Er, Yb and Lu). Using a combination of steady state, time-resolved, and transient absorption experiments, the influence on the photophysical properties of the metalloligand exerted by the different Ln(iii) cations has been investigated, together with the energy transfer efficiency from the metalloligand to the Ln(iii) 4f* excited state.

Soluble PtII-Containing Polymers Based on a 2,6-Bis(1H-1,2,3-triazol-4-yl)-4-ethynylpyridine Ligand

A soluble Pt^II-acetylide polymer 6 was prepared in a supramolecular polymerization of a Pt^II-chloro precursor complex 5, which represents a self-complementary AB-type monomer. This new type of polymer combines the structural features of the common polyplatinynes and cationic Pt^II-acetylide complexes. Though the photophysical and electrochemical properties of the material still need to be advanced, a versatile and straightforward method for the preparation of soluble, cationic Pt^II-acetylide polymers with phosphorescent behavior is offered.

A luminescent europium(iii)–platinum(ii) heterometallic complex as a theranostic agent: a proof-of-concept study

We present a luminescent heterometallic multifunctional theranostic Eu–Pt₂ complex, [{cis-PtCl₂(DMSO)}₂Eu(L)(H₂O)], possessing two cytotoxic Pt-centers with four DNA-binding sites, which shows intracellular Eu-based red luminescence sensitized by platinum based MLCT excited states.

Substitutional photoluminescence modulation in adducts of a europium chelate with a range of alkali metal cations: a gas-phase study

We present gas-phase dispersed photoluminescence spectra of europium(III) 9-hydroxyphenalen-1-one (HPLN) complexes forming adducts with alkali metal ions ([Eu(PLN)3M](+) with M = Li, Na, K, Rb, and Cs) confined in a quadrupole ion trap for study. The mass selected alkali metal cation adducts display a split hypersensitive (5)D0 → (7)F2 Eu(3+) emission band. One of the two emission components shows a linear dependence on the radius of the alkali metal cation whereas the other component displays a quadratic dependence thereon. In addition, the relative intensities of both components invert in the same order. The experimental results are interpreted with the support of density functional calculations and Judd-Ofelt theory, yielding also structural information on the isolated [Eu(PLN)3M](+) chromophores.