Luminescent gels by self-assembling platinum complexes

A platinum complex bearing a tetraethylene glycol chain has been designed and its self-assembly properties investigated. In solution, only a yellow phosphorescence of the aggregated species is observed. The complex gives luminescent gels of different colours with DCM and DMF, reaching up to 60% photoluminescence quantum yield. \ua9 2012 The Royal Society of Chemistry

Tuning the structural and photophysical properties of cationic Pt(II) complexes bearing neutral bis(triazolyl)pyridine ligands

The emission properties of a series of cationic Pt(II) complexes bearing neutral tridentate 2,6-bis-(1H-1,2,3-triazol-5-yl)pyridine and monoanionic ancillary ligands (Cl- or CN-) are described. By varying the substitution pattern on the 1,2,3-triazole moieties of the tridentate luminophore and the nature of the ancillary ligand, we were able to tune the intermolecular interactions between the complexes and therefore the electronic interactions between the metal centers. Indeed, all the compounds possessing Cl- as ancillary ligand are nonluminescent at room temperature, while the complexes containing CN- are luminescent. Interestingly, the \u3c0-accepting nature of this ancillary ligand induces Pt(II)-Pt(II) interactions irrespectively of bulky substitution patterns on the tridentate ligand

Tracking intramolecular interactions in flexibly linked binuclear Platinum(II) complexes

In this work we describe the synthesis and the photophysical and electrochemical characterization of binuclear PtII complexes. Using a modular click chemistry approach, we decorated different flexible bridging units with (bpy)PtII bisacetylides (bpy = 2,2\u2032-bipyridine). Intramolecular excimer formation originating from PtII-Pt II and \u3c0-\u3c0 interactions was investigated by steady-state and time-resolved emission spectroscopy in dilute solution. We observed that linkers bringing the metallic centers in close proximity favor both ground-state coupling and excimer formation. These interactions lead to changes in the photophysical and electrochemical properties, which can be tuned by the choice of solvent

Bidirectional photoinduced energy transfer in nanoassemblies of quantum dots and luminescent metal complexes

This work describes the synthesis and photophysical characterization of Ir(III) and Ru(II) complexes bearing terminal amino groups, which act as anchoring units for the attachment to quantum dots, QDs. The photophysical properties of the metal complexes in combination with different types of QDs, allows directional photoinduced processes in the assemblies. In particular, we show photoinduced energy transfer from the luminescent excited Ir(III) unit to the CdTe nanocrystals, with an efficiency of 40%. The directionality was then inverted by employing an emitting Ru(II) complex as energy acceptor, in combination with photoluminescent CdSe/ZnS quantum dots. The efficiency of the photoinduced energy transfer from the nanocrystals to the Ru(II) center was estimated to be as high as 75%. This work provides model systems for nanoassemblies based on quantum dots and metal complexes for optoelectronic applications, and as active light-harvesting systems

Agglutination of bacteria using poyvalent nanoparticles of aggregation-induced emissive thiophthalonitrile dyes

A novel class of aggregation-induced emissive bis(phenylthio)phthalonitrile dyes were synthesized. These dyes assembled into nanoparticles that were equipped with mannose units. The nanoparticles underwent selective interactions with lectins and bacteria. The bright fluorescent aggregates aid in the visualization of the agglutination of bacteria

The ecology and control of fireweed (Senecio madagascariensis Poir)

The improvement of molecular electronic devices such as organic light-emitting diodes requires fundamental knowledge about the structural and electronic properties of the employed molecules as well as their interactions with neighboring molecules or interfaces. We show that highly resolved scanning tunneling microscopy (STM) and spectroscopy (STS) are powerful tools to correlate the electronic properties of phosphorescent complexes (i.e., triplet emitters) with their molecular structure as well as the local environment around a single molecule. We used spectroscopic mapping to visualize several occupied and unoccupied molecular frontier orbitals of Pt(II) complexes adsorbed on Au(111). The analysis showed that the molecules exhibit a peculiar localized strong hybridization that leads to partial depopulation of a dz² orbital, while the ligand orbitals are almost unchanged. We further found that substitution of functional groups at well-defined positions can alter specific molecular orbitals without influencing the others. The results open a path toward the tailored design of electronic and optical properties of triplet emitters by smart ligand substitution, which may improve the performance of future OLED devices

Sensitisation of the near-infrared emission of NdIII from the singlet state of porphyrins bearing four 8-hydroxyquinolinylamide chelates

The \u3b14 atropoisomer of a tetraaryl porphyrin and its PdII complex, both bearing four hydroxyquinolinyl chelating units pre-organised on the same face of the porphyrin backbone, bind a Nd III centre thus affording either a mononuclear or a heterobinuclear anionic species, respectively. The near-infrared emission of the lanthanide centred at 1064 nm is observed upon excitation of the Soret band at 425 nm. Sensitisation proceeds mainly from the singlet state of the porphyrin

Bidentate NHC pyrozolate ligands in luminescent platinum(ii) complexes

A bidentate C^N donor set derived from an N-heterocyclic carbene (NHC) precursor linked to a trifluoromethyl (CF3) functionalized pyrazole ring is described for the first time. The ligands have been employed to prepare four new phosphorescent complexes by the coordination of platinum(ii) centres bearing cyclometalated phenyl-pyridine/triazole-pyridine chelates. The electronic and steric environments of these complexes were tuned through the incorporation of suitable substituents in the phenyl-pyridine/triazole-pyridine ligands, wherein the position of the phenyl-ring substituent (a CF3 group) also directs the selective adoption of either a trans or a cis configuration between the CNHC and the Cphenyl donor atoms. Molecular structures obtained by X-ray diffraction for three of the complexes confirm a distorted square-planar configuration around the platinum centre, and DFT calculations show that the substituents have a significant influence on the energies of the frontier orbitals. Moreover, a platinum(ii) complex featuring the new bidentate NHC^pyrazolate ligand and a bulky adamantyl functionalized pyridine-triazole luminophore was observed to be highly emissive and exhibiting a sky-blue luminescence (\u3bbEm = 470 nm) with photoluminescence quantum yields as high as 50% in doped PMMA matrices. A complete photophysical investigation of all of the complexes in solution as well as in the solid state is herein reported

Photoactive hybrid nanomaterial for targeting, labeling, and killing antibiotic-resistant bacteria

Killing with light: A multifunctional nanosized zeolite L uses amino groups, a luminescent dye, and a 1O2 producer to target, label, and kill pathogenic and antibiotic-resistant bacteria

Correlating the Structural and Photophysical Features of Pincer Luminophores and Monodentate Ancillary Ligands in Pt-II Phosphors

Phosphorescent PtII complexes featuring pincer luminophores of 2,6-bis(1,2,4-triazolyl)pyridine (H2L1) and 2,6-bis(pyrazolyl)pyridine (H2L3) with a bulky adamantyl or tolyl substituent (H2L4) are systematically compared, and their structural features are correlated with their photophysical properties. The combination with 4-amylpyridine (Py), triphenylphosphine (P) or benzimidazol-2-ylidene (N-heterocyclic carbene, NHC) donors as monodentate ancillary ligands gave a series of highly luminescent triplet emitters with variable aggregation properties. The molecular structures of four of these complexes, namely, Pt-L1-P, Pt-L1-NHC, Pt-L3-P, and Pt-L4-P were garnered from single-crystal X-ray diffraction analysis. The coordination complexes displayed green phosphorescence in solution and in the solid state. In doped poly(methyl methacrylate) (PMMA) matrices, most of the complexes exhibited high phosphorescence quantum yields, which reached 59 % for Pt-L3-P. A comparative analysis between the spectroscopic data and the computed parameters derived from time-dependent density functional theory (TD-DFT) calculations suggests that the emission originates from metal-perturbed ligand-centered excited triplet states (3MP-LC). The radiationless deactivation rate constants of the emissive states can be correlated with the aggregation properties derived from the substitution pattern at the tridentate luminophores and the ancillary ligands, whereas the radiative rate constants are determined by the electronic structures of the complexes. We found that PtII complexes containing pyrazolate donors showed an enhanced charge-transfer character in the excited state, whereas bulky adamantyl moieties and triphenylphosphine ancillary ligands suppress bimolecular aggregation and quenching phenomena