Controlling the aggregation of planar photosensitizers and electroluminescent materials

Conferencia Científica del Dpto. Química OrgánicaAggregation of planar chromophores greatly affects their photophysical performance. It is possible to avoid the aggregation of phthalocyaninates by axially binding them to the surface of aluminosilicates. We have recently designed a multifunctional zeolite L-based hybrid material able to target, label and photoinactivate pathogenic and antibiotic resistant bacteria.[1,2] The outer surface was functionalized with a Si(IV) phthalocyanine derivative that forms toxic singlet oxygen upon red light irradiation, and with amino groups for targeting the living microorganisms. Currently, we aim to extend these concepts to targeted, fully soluble and biodegradable platforms, a prerequisite for biomedical applications.[3,4] We have recently developed a straightforward one-pot synthesis of neutral, soluble Pt(II) coordination compounds bearing dianionic tridentate ligands. The complexes reached up to 87% photoluminescence quantum yield (PLQY) in thin films, with concentration independent colour and efficiency.[5] Consequently, we demonstrated their suitability as phosphorescent dopants in organic light-emitting diodes (OLEDs). Furthermore, the judicious choice of bulky peripheral substituents allowed us to completely prevent aggregation and to enhance color purity, a critical aspect when designing triplet emitters for electroluminescent devices.[6] On the other hand, we were able to deliberately induce self-assembly into bright nanofibers, which can interlock to yield highly emissive organo- and hydrogels (90% PLQY), thus constituting a versatile building block for luminescent architectures. The unique properties of the filaments arise from the metal-metal to ligand charge-transfer states of the aggregated species, which display strong Pt-Pt interactions. It is therefore possible to trace the self-assembly process with high sensitivity by monitoring the turn-on of the emission upon aggregation.[5] Currently, we investigate the electronic coupling between Pt(II) d-orbitals and electrodes at single molecule level, employing scanning tunnel microscopy and scanning tunnel spectroscopy.[7] Our results elegantly show how a careful, rational design allow us to fully control the aggregation of planar chromophores, and, consequently, to tune their photophysical and photochemical properties.Vicerrectorado de Investigación y Transferencia. Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

New nephridiophagid genera (Fungi, Chytridiomycota) in a mallow beetle and an earwig

Nephridiophagids are unicellular fungi (Chytridiomycota) that infect the Malpighian tubules of insects. Most species have been found in cockroach hosts and belong to the genus Nephridiophaga. Three additional genera have been described from beetles and an earwig. Here, we characterise morphologically and molecular phylogenetically the nephridiophagids of the European earwig Forficula auricularia and the mallow beetle Podagrica malvae. Their morphology and life cycle stages resemble those of other nephridiophagids, but their rRNA gene sequences support the existence of two additional genera. Whereas the earwig nephridiophagid (Nephridiochytrium forficulae gen. nov. et sp. nov.) forms a sister lineage of the Nephridiophaga cluster, the mallow beetle nephridiophagid (Malpighivinco podagricae gen. nov. et sp. nov.) represents the earliest divergent lineage within the nephridiophagids, being sister to all other species. Our results corroborate the hypothesis that different insect groups harbour distinct nephridiophagid lineages

The manufacture and products thereof of photo-sensitizing nanomaterials and their use in photodynamic treatments

A method for the manufacture of a photosensitizing nanoma terial (40) and the products thereof are disclosed. The method for the treatment of a biological target (50) is disclosed. The photosensitizing nanomaterial (40) comprises a metal com plex tetrapyrrole derivative (10). The metal complex tetrapy rrole derivative (10) is attached by an axial covalent bond (60) to the surface (25) of a solid nanomaterial (20). The solid nanomaterial (20) has at least one dimension in the nanometer and/ or the micrometer range

Long rDNA amplicon sequencing of insect-infecting nephridiophagids reveals their affiliation to the Chytridiomycota and a potential to switch between hosts

Nephridiophagids are unicellular eukaryotes that parasitize the Malpighian tubules of numerous insects. Their life cycle comprises multinucleate vegetative plasmodia that divide into oligonucleate and uninucleate cells, and sporogonial plasmodia that form uninucleate spores. Nephridiophagids are poor in morphological characteristics, and although they have been tentatively identified as early-branching fungi based on the SSU rRNA gene sequences of three species, their exact position within the fungal tree of live remained unclear. In this study, we describe two new species of nephridiophagids (Nephridiophaga postici and Nephridiophaga javanicae) from cockroaches. Using long-read sequencing of the nearly complete rDNA operon of numerous further species obtained from cockroaches and earwigs to improve the resolution of the phylogenetic analysis, we found a robust affiliation of nephridiophagids with the Chytridiomycota—a group of zoosporic fungi that comprises parasites of diverse host taxa, such as microphytes, plants, and amphibians. The presence of the same nephridiophagid species in two only distantly related cockroaches indicates that their host specificity is not as strict as generally assumed

Exploiting metallophilicity for the assembly of inorganic nanocrystals and conjugated organic molecules

The accurate engineering of interfaces between inorganic nanocrystals and semiconducting organic molecules is currently viewed as key for further developments in critical fields such as photovoltaics and photocatalysis. In this work, a new and unconventional source of interface interaction based on metal–metal bonds is presented. With this aim, an AuI organometallic gelator was exploited for the formation of hydrogel-like nanocomposites containing inorganic nanoparticles and conjugated organic molecules. Noteworthy, the establishment of metallophilic interactions at the interface between the two moieties greatly enhances interparticle coupling in the composites. Thus, we believe that this new hybrid system might represent a promising alternative in several fields, such as in the fabrication of improved light-harvesting devices.Peer ReviewedPostprint (author's final draft

Pt(II)-dendrimers as bio-imaging marker for bacteria in two-photon excitation microscopy

The use of luminescent markers based on metal complexes in two-photon excitation microscopy techniques are of great interest in the field of bioimaging. However, despite the excellent luminescent properties of Pt(II) complexes, their application in this field is still limited, due to their poor solubility and quenching problems in aqueous media [1]. The insertion of a Pt(II) complex into a dendritic structure, gives as a result an unique luminescent marker soluble in biological media. Dendrimers provides excellent properties to the metal complex such as solubility in aqueous media, protection against quenching processes and binding to bacterial surfaces. The new probe can be used as bacteria cells marker in luminescent microscopy, operating under one or two-photon excitation (OPE/TPE) conditions, as well as in electron microscopy, thus providing a powerful tool in the field of bioimaging.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Mixed-ligand lanthanide complexes supported by ditopic bis(imino-methyl)-phenol/calix[4]arene macrocycles: synthesis, structures, and luminescence properties of [Ln2(L2)(MeOH)2] (Ln = La, Eu, Tb, Yb)

The lanthanide binding ability of a macrocyclic ligand H6L2 comprising two bis(iminomethyl)phenol and two calix[4]arene units has been studied. H6L2 is a ditopic ligand which provides dinuclear neutral complexes of composition [Ln2(L2)(MeOH)2] (Ln = La (1), Eu (2), Tb (3), and Yb (4)) in very good yield. X-ray crystal structure analyses for 2 and 3 show that (L2)6- accommodates two seven coordinated lanthanide ions in a distorted monocapped trigonal prismatic/octahedral coordination environment. UV-vis spectroscopic titrations performed with La3+, Eu3+, Tb3+ and Yb3+ ions in mixed MeOH/CH2Cl2 solution (I = 0.01 M NBu4PF6) reveal that a 2 : 1 (metal : ligand) stoichiometry is present in solution, with log K11 and K21 values ranging from 5.25 to 6.64. The ratio α = K11/K21 of the stepwise formation constants for the mononuclear (L2 + M = ML2, log K11) and the dinuclear complexes (ML2 + M = M2L2, log K21) was found to be invariably smaller than unity indicating that the binding of the first Ln3+ ion augments the binding of the second Ln3+ ion. The present complexes are less luminescent than other seven-coordinated Eu and Tb complexes, which can be traced to vibrational relaxation of excited EuIII and TbIII states by the coligated MeOH and H2O molecules and/or low-lying ligand-to-metal charge-transfer (LMCT) states. © 2020 The Royal Society of Chemistry

Photophysical Study on the Rigid Pt(II) Complex [Pt(naphen)(Cl)] (Hnaphen = Naphtho[1,2-b][1,10]Phenanthroline and Derivatives

The electrochemistry and photophysics of the Pt(II) complexes [Pt(naphen)(X)] (Hnaphen = naphtho[1,2-b][1,10]phenanthroline, X = Cl or C≡CPh) containing the rigid tridentate C^N^N-coordinating pericyclic naphen ligand was studied alongside the complexes of the tetrahydro-derivative [Pt(thnaphen)(X)] (Hthnaphen = 5,6,8,9-tetrahydro-naphtho[1,2-b][1,10]phenanthroline) and the N^C^N-coordinated complex [Pt(bdq)(Cl)] (Hbdq = benzo[1,2-h:5,4-h’]diquinoline. The cyclic voltammetry showed reversible reductions for the C^N^N complexes, with markedly fewer negative potentials (around −1.6 V vs. ferrocene) for the complexes containing the naphen ligand compared with the thnaphen derivatives (around −1.9 V). With irreversible oxidations at around +0.3 V for all of the complexes, the naphen made a difference in the electrochemical gap of about 0.3 eV (1.9 vs. 2.2 eV) compared with thnaphen. The bdq complex was completely different, with an irreversible reduction at around −2 V caused by the N^C^N coordination pattern, which lacked a good electron acceptor such as the phenanthroline unit in the C^N^N ligand naphen. Long-wavelength UV-Vis absorption bands were found around 520 to 530 nm for the C^N^N complexes with the C≡CPh coligand and were red-shifted when compared with the Cl derivatives. The N^C^N-coordinated bdq complex was markedly blue-shifted (493 nm). The steady-state photoluminescence spectra showed poorly structured emission bands peaking at around 630 nm for the two naphen complexes and 570 nm for the thnaphen derivatives. The bdq complex showed a pronounced vibrational structure and an emission maximum at 586 nm. Assuming mixed 3LC/3MLCT excited states, the vibronic progression for the N^C^N bdq complex indicated a higher LC character than assumed for the C^N^N-coordinated naphen and thnaphen complexes. The blue-shift was a result of the different N^C^N vs. C^N^N coordination. The photoluminescence lifetimes and quantum yields ΦL massively increased from solutions at 298 K (0.06 to 0.24) to glassy frozen matrices at 77 K (0.80 to 0.95). The nanosecond time-resolved study on [Pt(naphen)(Cl)] showed a phosphorescence emission signal originating from the mixed 3LC/3MLCT with an emission lifetime of around 3 µs