Reversible Piezochromism of Platinum(II) and Palladium(II) Dimers in Molecular Single Crystals.

Transition metal complexes are well-known for their efficient light emission and are promising for applications ranging from bioimaging to light-emitting diodes. In solution, interactions between the metal centers of two complexes become possible and drastically change the photophysical properties. For real-world devices, solid-state materials consisting of these molecules are preferable.

Stepwise Modulation of Bridged Single-Benzene-Based Fluorophores for Materials Science.

In recent years, researchers studying fluorogenic samples have steadily shifted from using large, expensive, poorly soluble fluorophores with complex synthetic sequences to smaller, simpler π scaffolds with low molecular weight. This research article presents an in-depth study of the photophysical properties of five bridged single-benzene-based fluorophores (SBBFs) investigated for their solution and solid-state emission (SSSE) properties. The compounds O, NO, NO, NO, and N are derived from a central terephthalonitrile core and vary in the amount of oxygen and nitrogen bridging atoms.

Heterobimetallic contacts in statistical co-crystals of homoleptic coordination compounds with ligand-encoded H⋯F bonds: structure, photophysics and mechano-responsive properties.

In this work, the structural and photophysical characterization of statistical co-crystals based on two homoleptic Pt(II) and Pd(II) complexes as well as their mechano-responsive properties are reported. Ligand-dominated H⋯F bonds, which reinforce metal-metal interactions in the crystalline state, support emission from MMLCT states. All co-crystals show a distinct red-shift upon grinding, showcasing their inherent mechano-responsive characteristics stemming from (hetero-)bimetallic contacts.

Photoresponsive Luminescent Silica Nanoparticles as Additive for 3D Printing and Electrospinning.

In this study, we present the synthesis and a versatile way to incorporate photoresponsive organic luminophores into polymeric materials using mesoporous silica nanoparticles (MSNs). The encapsulated thioethers within the MSNs were employed in polyvinyl alcohol (PVA) films, resin-based stereolithography, and electrospinning. Due to light-induced cyclisation to dibenzothiophenes (DBTs), mmOC loaded materials were used to inscribe images using UV light.

Pathway-dependent Metallosupramolecular Polymerization Regulated by Ligand Geometry.

Understanding structure/property correlations in self-assembly is a key but challenging requirement for developing functional materials. Herein, we explore the importance of ligand geometry to fine-tune photophysical properties (MMLCT vs. MLCT excited states) and self-assembly pathways in metallosupramolecular polymerization.

In situ Cyclization of Aromatic Thioethers in Emissive Materials to Generate Phosphorescent Dibenzothiophenes.

In this contribution, we explored the photocyclization of thioethers to highly substituted dibenzothiophenes (DBT) using solely UV-light without any need for additives. This cost-effective, robust and environmentally friendly approach yielded phosphorescent compounds, which were characterized by X-ray crystallography and state-of-the-art photophysical methods. The resulting DBTs feature ultralong photoluminescence lifetimes and quantum yields close to unity in frozen glassy matrices.

Molecular folding governs switchable singlet oxygen photoproduction in porphyrin-decorated bistable rotaxanes.

Rotaxanes are mechanically interlocked molecules where a ring (macrocycle) is threaded onto a linear molecule (thread). The position of the macrocycle on different stations on the thread can be controlled in response to external stimuli, making rotaxanes applicable as molecular switches. Here we show that bistable rotaxanes based on the combination of a Zn(II) tetraphenylporphyrin photosensitizer, attached to the macrocycle, and a black-hole-quencher, attached to the thread, are capable of singlet oxygen production which can be switched on/off by the addition of base/acid.

Merging of a Supramolecular Ligand with a Switchable Luminophore - Light-Responsiveness, Photophysics and Bioimaging.

In this contribution we report on a novel approach towards luminescent light-responsive ligands. To this end, cyanostilbene- guanidiniocarbonyl-pyrrole hybrids were designed and investigated. Merging of a luminophore with a supramolecular bioactive ligand bears numerous advantages by overcoming the typical drawbacks of drug-labelling, influencing the overall performance of the active species by attachment of a large luminophore.

Assessing the Character of the CF Ligand from the Electrochemical and Photophysical Properties of [Ni(CF)(NN)] Complexes.

Organonickel complexes containing α-diimine ligands [Ni(CF)(NN)] (NN = 2,2'-bipyridine (bpy), 2,9-dimethyl-1,10-phenanthroline (dmphen), 3,4,7,8-tetramethyl-1,10-phenanthroline (tmphen), dipyrido[3,2-:2',3'-]phenazine (dppz), 1,4-bis(isopropyl)-1,4-diazabutadiene (Pr-DAB), and 1,4-bis(2,6-dimethylphenyl)-1,4-diazabutadiene (Xyl-DAB) were prepared and studied structurally, spectroscopically, and electrochemically. Their molecular structures from single-crystal X-ray diffraction show near-perfect square planar Ni(II) coordination except in the case of dmphen. Primary reversible electrochemical reductions in the range from -1 to -2 V vs ferrocene/ferrocenium couple lead to mainly diimine-localized radical anion complexes, while secondary reductions in the range from -2 to -2.

Antiprotozoal Pt(II) Complexes as Luminophores Bearing Monodentate P/As/Sb-Based Donors: An X-ray Diffractometric, Photoluminescence, and Sb- Spectroscopic Study with TD-DFT-Guided Interpretation and Predictive Extrapolation toward Bi.

In this study, it is demonstrated that the radiative rate constant of phosphorescent metal complexes can be substantially enhanced using monodentate ancillary ligands containing heavy donor atoms. Thus, the chlorido coligand from a Pt(II) complex bearing a monoanionic tridentate C^N*N luminophore ([]) was replaced by triphenylphosphane (PPh) and its heavier pnictogen congeners (i.e.

A Case-Study on the Photophysics of Chalcogen-Substituted Zinc(II) Phthalocyanines.

Singlet dioxygen has been widely applied in different disciplines such as medicine (photodynamic therapy or blood sterilization), remediation (wastewater treatment) or industrial processes (fine chemicals synthesis). Particularly, it can be conveniently generated by energy transfer between a photosensitizer's triplet state and triplet dioxygen upon irradiation with visible light. Among the best photosensitizers, substituted zinc(II) phthalocyanines are prominent due to their excellent photophysical properties, which can be tuned by structural modifications, such as halogen- and chalcogen-atom substitution.

Activating the Fluorescence of a Ni(II) Complex by Energy Transfer.

Luminescence of open-shell 3 metal complexes is often quenched due to ultrafast intersystem crossing (ISC) and cooling into a dark metal-centered excited state. We demonstrate successful activation of fluorescence from individual nickel phthalocyanine (NiPc) molecules in the junction of a scanning tunneling microscope (STM) by resonant energy transfer from other metal phthalocyanines at low temperature. By combining STM, scanning tunneling spectroscopy, STM-induced luminescence, and photoluminescence experiments as well as time-dependent density functional theory, we provide evidence that there is an activation barrier for the ISC, which, in most experimental conditions, is overcome.

Cyanido-bridged diplatinum(ii) complexes: ligand and solvent effect on aggregation and luminescence.

The association of platinum(ii)-based luminophores, which is caused by metal⋯metal and π-π stacking interactions, has been actively exploited in supramolecular construction of photofunctional molecular materials. Herein, we describe a series of bimetallic complexes [{Pt(C^N^*N)}(CN)][BAr], containing cyanido-bridged cyclometalated Pt(ii) chromophore fragments (HC^N^N = 6-phenyl-2,2'-bipyridine, (benzyltriazolyl)-phenylpyridine, and pyrazolyl-phenylpyridine; HC^N*N = -pentyl-6-phenyl--(pyridin-2-yl)pyridin-2-amine; ^/* denote five/six-membered metallocycles). These compounds are intensely phosphorescent at room temperature showing quantum yields up to 0.

Dual Emissive Zn(II) Naphthalocyanines: Synthesis, Structural and Photophysical Characterization with Theory-Supported Insights towards Soluble Coordination Compounds with Visible and Near-Infrared Emission.

Metal phthalocyaninates and their higher homologues are recognized as deep-red luminophores emitting from their lowest excited singlet state. Herein, we report on the design, synthesis, and in-depth characterization of a new class of dual-emissive (visible and NIR) metal naphthalocyaninates. A 4-,-dimethylaminophen-4-yl-substituted naphthalocyaninato zinc(II) complex () and the derived water-soluble coordination compound () exhibit a near-infrared fluorescence from the lowest ligand-centered state, along with a unique push-pull-supported luminescence in the visible region of the electromagnetic spectrum.

Neutral and Cationic Re(I) Complexes with Pnictogen-Based Coligands and Tunable Functionality: From Phosphorescence to Photoinduced CO Release.

In this work, we have explored Re(I) complexes featuring triphenylpnictogen (, = , , or )-based coligands and bidentate (neutral or monoanionic) luminophores derived from 1,10-phenantroline (), as well as from 2-(3-(-butyl)-1-1,2,4-triazol-5-yl)pyridine (). The effect of the increasingly heavy elements on the structural parameters, photoexcited-state properties, and electrochemical behavior as well as the hybridization defects and polarization of the atoms was related to the charges of the main luminophores (i.e.

One Dianionic Luminophore with Three Coordination Modes Binding Four Different Metals: Toward Unexpectedly Phosphorescent Transition Metal Complexes.

This work reports on a battery of coordination compounds featuring a versatile dianionic luminophore adopting three different coordination modes (mono, bi, and tridentate) while chelating Pd(II), Pt(II), Au(III), and Hg(II) centers. An in-depth structural characterization of the ligand precursor (H L) and six transition metal complexes ([HLPdCNtBu], [LPtCl], [LPtCNtBu], [LPtCNPhen], [HLHgCl], and [LAuCl]) is presented. The influence of the cations and coordination modes of the luminophore and co-ligands on the photophysical properties (including photoluminescence quantum yields (Φ ), excited state lifetimes (τ), and average (non-)radiative rate constants) are evaluated at various temperatures in different phases.

The Effect of Monodentate Co-Ligands on the Properties of Pt(II) Complexes Bearing a Tridentate C^N*N-Luminophore.

In this study, the insertion of different monodentate co-ligands on Pt(II) complexes bearing a monoanionic C^N*N luminophore as a tridentate chelator was achieved beyond the previously reported chlorido- ([]) and cyanido-decorated ([]) analogues. To investigate the impact of the auxiliary ligand on the photophysical properties, we introduced a neutral carbonyl-ligand and observed a lower photoluminescence quantum yield () than with a cyanido moiety. However, the direct substitution of the chlorido co-ligand by a NO-related derivative was not successful.

Enhanced luminescence properties through heavy ancillary ligands in [Pt(C^N^C)(L)] complexes, L = AsPh and SbPh.

In the frame of our research aiming to develop efficient triplet-emitting materials, we are exploring the concept of introducing additional heavy atoms into cyclometalated transition metal complexes to enhance intersystem-crossing (ISC) and thus triplet emission through increased spin-orbit coupling (SOC). In an in-depth proof-of-principle study we investigated the double cyclometalated Pt(II) complexes [Pt(C^N^C)(PnPh)] (HC^N^CH = 2,6-diphenyl-pyridine (Hdpp) or dibenzoacridine (Hdba); Pn = pnictogen atoms P, As, Sb, or Bi) through a combined experimental and theoretical approach. The derivatives containing Pn = P, As, and Sb were synthesised and characterised comprehensively using single crystal X-ray diffraction (scXRD), UV-vis absorption and emission spectroscopy, transient absorption (TA) spectroscopy and cyclic voltammetry (CV).

Pt(II) Complexes with Tetradentate C^N*N^C Luminophores: From Supramolecular Interactions to Temperature-Sensing Materials with Memory and Optical Readouts.

A series of four regioisomeric Pt(II) complexes ( and ) bearing tetradentate luminophores as dianionic ligands were synthesized. Hence, both classes of cyclometallating chelators were decorated with three -hexyl ( = 6) or -dodecyl ( = 12) chains. The new compounds were unambiguously characterized by means of multiple NMR spectroscopies and mass spectrometry.

Enhanced Solid-State Fluorescence of Flavin Derivatives by Incorporation in the Metal-Organic Frameworks MIL-53(Al) and MOF-5.

The flavin derivatives 10-methyl-isoalloxazine (MIA) and 6-fluoro-10-methyl-isoalloxazine (6F-MIA) were incorporated in two alternative metal-organic frameworks, (MOFs) MIL-53(Al) and MOF-5. We used a post-synthetic, diffusion-based incorporation into microcrystalline MIL-53 powders with one-dimensional (1D) pores and an in-situ approach during the synthesis of MOF-5 with its 3D channel network. The maximum amount of flavin dye incorporation is 3.

Facile modification of phosphole-based aggregation-induced emission luminogens with sulfonyl isocyanates.

Phosphole oxides undergo a highly chemoselective reaction with sulfonyl isocyanates forming sulfonylimino phospholes in high yields. This facile modification proved to be a powerful tool for obtaining new phosphole-based aggregation-induced emission (AIE) luminogens with high fluorescence quantum yields in the solid state. Changing the chemical environment of the phosphorus atom of the phosphole framework results in a significant shift of the fluorescence maximum to longer wavelengths.

Site-specific covalent metalation of DNA oligonucleotides with phosphorescent platinum(ii) complexes.

Phosphorescent Pt(II) complexes, composed of a tridentate N^N^C donor ligand and a monodentate ancillary ligand, were covalently attached to DNA oligonucleotides. Three modes of attachment were investigated: positioning the tridentate ligand as an artificial nucleobase a 2'-deoxyribose or a propane-1,2-diol moiety and orienting it towards the major groove by appending it to a uridine C5 position. The photophysical properties of the complexes depend on the mode of attachment and on the identity of the monodentate ligand (iodido cyanido ligand).

Room-Temperature Phosphorescence from Pd(II) and Pt(II) Complexes as Supramolecular Luminophores: The Role of Self-Assembly, Metal-Metal Interactions, Spin-Orbit Coupling, and Ligand-Field Splitting.

The synthesis as well as the structural and photophysical characterization of two isoleptic bis-cyclometalated Pt(II) and Pd(II) complexes, namely [] and [], bearing a tailored dianionic tetradentate ligand () are reported. The isostructural character and intermolecular interactions of [] and [] were assessed by NMR spectroscopy and X-ray diffraction analysis. Both complexes show fully ligand-controlled aggregation, demonstrating that a judicious molecular design can tune the photophysical properties.