Novel anda Highly Efficient Cycloplatinated NHC Complexes for the Generation of White Light

La tecnología LED y OLED ha irrumpido en el campo de la iluminación y actualmente se considera una alternativa para reemplazar a las ya prohibidas lámparas incandescentes y fluorescentes dado su menor consumo energético. Tanto los WLEDs como los WOLEDs, emisores de luz blanca empleados en iluminación, incorporan metales de tierras raras cuyo mercado está controlado en un 85% por China. Esto supone un elevado riesgo de desabastecimiento y precio, lo que puede afectar dramáticamente a la industria mundial. En este sentido el uso de compuestos organometálicos de metales de transición como rutenio, osmio, iridio y platino con propiedades luminiscentes se considera una alternativa a los WLEDs y WOLEDs convencionales. La elevada constante de acoplamiento spin-orbita (ξ) en estos metales pesados permite la relajación de las reglas de selección que dictan las transiciones energéticas permitidas y prohibidas, de modo que los procesos de fosforescencia pueden tener lugar de forma eficiente. Como consecuencia, los máximos rendimientos cuánticos teóricos ascienden a la unidad, dando lugar a materiales funcionales con un mayor potencial para aplicaciones de bajo consumo energético.Nuestro trabajo se ha centrado en la síntesis y caracterización de nuevos derivados luminescentes de Pt(II) y la implementación de alguno de ellos en dispositivos emisores de luz blanca. Los compuestos preparados contienen un cromóforo del tipo “Pt(R-C^C*)” dónde R-C^C* es un ligando carbeno N-heterocíclico ciclometalado. La presencia de dos enlaces Pt-C aumenta el desdoblamiento de los orbitales del metal respecto a los ligandos C,N-ciclometalados, más conocidos y estudiados, y aporta una gran estabilidad física y química a los compuestos.Para desarrollar este trabajo, se prepararon los complejos [{Pt(μ-Cl)(R-C^C*)}2] siguiendo un protocolo en varios pasos desarrollado y empleado exclusivamente en nuestro grupo de investigación. Los complejos [{Pt(μ-Cl)(R-C^C*)}2] resultaron ser excelentes precursores de compuestos con diversas estequiometrías: [PtCl(NC-C^C*)L], [Pt(NC-C^C*)PPh3L], [Pt(R-C^C*)(CNR’)2]PF6, NBu4[Pt(R-C^C*)(CN)2], [Pt(R-C^C*)(P^P)]PF6 y [Pt(R-C^C*)(acac)] que a su vez pueden servir de precursores de compuestos con enlaces metal-metal, como [{Pt(R-C^C*)(acac)}2Tl]PF6. Todos los compuestos preparados han sido exhaustivamente caracterizados por diferentes técnicas, siendo las más significativas: IR, RMN y difracción de rayos X. Se ha llevado a cabo también la determinación de las propiedades fotofísicas de todos los compuestos preparados y su estudio mediante cálculos teóricos DFT/TD-DFT. Tal y como planteamos este trabajo, la mayor parte de los compuestos preparados han resultado ser emisores de luz azul bastante eficientes. Teniendo en cuenta que la luz azul es el componente esencial de la luz blanca, se ha estudiado la potencial aplicación de varios de ellos en diversos dispositivos emisores de luz blanca, con resultados prometedores.El conocimiento logrado acerca de estos sistemas puede facilitar un diseño racional de futuros materiales funcionales. <br /

Self-assembly of supramolecular architectures in solution and on surfaces

Supramolecular chemistry gives powerful tools to scientists for fabrication of new functional materials. Constant studies over nature of multiple interactions in biological systems, their application in chemistry and material science, finally fabrication of new devices available for wide community, allow progress and help humanity in everyday life. The present thesis is focused on design of applied supramolecular architectures for fascinating applications in material science, synthesis of building blocks for these systems and final assembly of subunits into functional materials, when possible. Main part of thesis harvest exceptional complexation properties of tetraphosphonate cavitands towards charged organic ammonium salts. They have been employed for building hierarchical luminescent complexes on silicon (Chapter 3), synthesis of luminescent dyes aligning in liquid crystal displays (Chapter 4), sensing of charged amines in water environment (Chapter 7), and their model compound, metal bridged cavitands, have been synthesized as building blocks for metal organic frameworks (Chapter 2). Second part of thesis is focused on chemistry of phthalocyanines, synthetic macromolecules with particular optical and electronic properties, which upon proper functionalization and organization on the surfaces can find applications in organic photovoltaics as very strong light absorbents and electron donors/acceptors (Chapter 5). Sandwich complexes with terbium opened area of new applications in spintronics due to its single molecule magnet properties (Chapter 6), where rational organization on surfaces is crucial

Nanoparticle-based Approaches to Brain Injury and Studies for Improved Detectability toward Better Delivery Characterization

The clinical translation of nanoparticle (NP) therapeutics for brain injury has been slow despite preclinical promise. The causes of disconnect between preclinical and clinical outcomes is multifactorial, but insufficient delivery is noteworthy. Preclinical delivery characterization often lacks, obscuring mechanisms of failure, slowing development. Multimodal imaging is a promising strategy to improve delivery characterization, combining the strengths of various modalities. Magnetic resonance imaging (MRI) and luminescence imaging are a suitable combination for multimodal imaging, expanding the spatial and temporal resolution of either alone, but further material development is needed to enhance detectability. One problem is the interference of cellular autofluorescence in luminescence imaging. The use of sensitized lanthanide luminophores, with emission lifetimes multiple orders of magnitude longer than autofluorescence, has been shown as an effective interference mitigation strategy in small molecule chelates as well as NP systems. This dissertation covers the assessment of several surface-coordinating ligands for enhanced photoluminescence of ultrasmall Eu2O3 NPs. Among the tested species, quinaldic acid (QA) and kynurenic acid (KA) were previously unreported for the sensitization of NPs, while terephthalic acid (TA) was previously used in a different Eu NP model. NP characterization showed consistent core structure, effective ligand coordination, and enhancement of Eu3+ emissions over tissue lysate autofluorescence. TA, QA, and KA provided signal-to-tissue-noise fold enhancements of 75, 89, and 108, respectively with time-gating. KA was further investigated as a co-sensitizer with DPA to enable the UV-A excitation of KA while passivating the surface with DPA to enhance emission intensity and lifetime. Using KA with DPA enhanced Eu3+ emission relative to tissue lysate autofluorescence, providing a 797-fold increase with time-gating. Comparison of that co-sensitized NP to Rhodamine B in a model of mounted tissue imaging showed a 15-fold improvement in detection limit on a number concentration basis. This work showed the efficacy of Eu sensitization with novel species, and it motivates further investigation toward mixed Gd/Eu NPs for multimodal imaging. Advisor: Forrest M. Kievi

Crystal Structures of Metal Complexes

This reprint contains 11 papers published in a Special Issue of Molecules entitled "Crystal Structures of Metal Complexes". I will be very happy if readers will be interested in the crystal structures of metal complexes

The Art of Formulation od Perfluorocarbon Encapsulated Polymeric PLGA Nanoparticles

This research work is focused on the encapsulation of perfluoro-15-crown-ether (PFCE) within polymeric NPs using the PLGA polymer as a contrast agent (CA) for MRI and examines multiple facets of the formulation process. The thesis is structured into 5 chapters : Chapter 2 “Nanotechnology as a Versatile Tool for 19F-MRI Agent’s Formulation: A Glimpse into the Use of Perfluorinated and Fluorinated Compounds in Nanoparticles” : This chapter offers an in-depth literature review on cutting-edge carrier systems for encapsulating PFCs. It provides insights into the utilization of perfluorinated and fluorinated compounds within NP frameworks. Chapter 3 “The Art of Preparations of PFCE Encapsulated PLGA Nanoparticles : Formulation and optimisation using High Speed Homogenization and Ultrasonication” The focus of this chapter is the formulation and optimization of PLGA NPs containing perfluoro-15-crown-ether (PFCE). It examines the impact of varying molecular weights of PLGA and the role of surfactants in the formulation process, utilizing techniques such as homogeniser and ultrasonic sonication for emulsion formation. Chapter 4 “Central Composite Design of Experiment Based Optimization of Key Formulation Parameters for PFCE- Encapsulated PLGA Nanoparticles”. A statistical approach is adopted to explore the parameters critical to the nanoformulation of PLGA-PFCE. This chapter delves into the methodical aspects that underpin the successful preparation of these NPs. Chapter 5 “Strategic Enhancement of PLGA Nanoparticles: PEG and Fluorine Additions for PFCE Encapsulation” – These chapters document the exploration of PLGA modification with polyethylene glycol (PEG) to increase the circulation time of the NPs and fluorine to increase the PFCE loading, employing advanced cerium catalysts. The modifications aim to enhance the preparation process of PFCE-encapsulated PLGA NPs. Finally, Chapter 6 “Conclusion and future perspectives” This section provides a comprehensive overview and analytical examination of the results derived from this thesis. It also contemplates potential enhancements and the broader clinical implementation of the formulations

Controlled Assembly of Endohedrally-Functionalized Metal-Ligand Supramolecular Complexes

An area of supramolecular chemistry that has recently been growing in popularity is the synthesis of metal-ligand cages. These are most commonly comprised of organic ligands and transition metal ions. Cage complexes often take the form of geometric polyhedra such as tetrahedra and octahedra, where the ligands act as the edges or faces and the metals serve as the vertices. Because these complexes have a polyhedral design, there is a central cavity in the cage, and this has been exploited for guest binding. Many types of guests have been bound inside supramolecular cage complexes, and binding is dependent on the environment inside the cage. Encapsulated guests can also react, either with themselves or with a coencapsulated guest. Host-guest chemistry is often inspired by the selectivity of enzymes for their substrates, and the development of biomimetic systems is one of the goals for these assemblies. While encapsulation has been effective for promoting reactions and accessing novel reactivity, reactions are limited to those that require no additional reagents such as cycloadditions. No functional groups are present to direct reactivity, and reactivity is promoted by an increased effective concentration of guest molecules in the confined interior of a host. Introducing functional groups to cages can mimic the side chains of amino acids that are present in enzyme active sites, and this strategy can lead to more specialized, truly biomimetic reactivity. This work presents a series of supramolecular cage complexes with varied geometries and assembly properties. Endohedral functionality could be introduced to a series of palladium-pyridine "paddle-wheel" complexes, and functional groups were able to influence assembly. Bidentate hydroxamic acid ligands were shown to complex bismuth and praseodymium, and attempts toward endohedrally-functionalizing these assemblies are discussed. Variable assembly was observed in complexes with 9-coordinate bismuth, and assembly was primarily dependent on metal concentration. Lanthanide complexes were also synthesized, and cooperative, thermodynamic control of selectivity between metal ions was observed. Fluorene-based ligands were combined with lanthanide ions, and complexes differing only in endohedral functionality narcissistically self-sorted despite identical ligand geometry and metal coordinating motif

Soluble dendrimers europium(III) β-diketonate complex for organic memory devices

We report the synthesis of a soluble dendrimers europium(III) complex, tris(dibenzoylmethanato)(1,3,5-tris[2-(2′-pyridyl)benzimidazoly]methylbenzene)-europium(III), and its application in organic electrical bistable memory device. Excellent stability that ensured more than 106 write-read-erase-reread cycles has been performed in ambient conditions without current-induced degradation. High-density, low-cost memory, good film-firming property, fascinating thermal and morphological stability allow the application of the dendrimers europium(III) complex as an active medium in non-volatile memory devices. © 2007 Elsevier B.V. All rights reserved