Novel synthetic approach to heteroatom doped polycyclic aromatic hydrocarbons: Optimizing the bottom-up approach to atomically precise doped nanographenes

The success of the rational bottom-up approach to nanostructured carbon materials and the discovery of the importance of their doping with heteroatoms puts under the spotlight all synthetic organic approaches to polycyclic aromatic hydrocarbons. The construction of atomically precise heteroatom doped nanographenes has evidenced the importance of controlling its geometry and the position of the doping heteroatoms, since these parameters influence their chemical–physical properties and their applications. The growing interest towards this research topic is testified by the large number of works published in this area, which have transformed a once “fundamental research” into applied research at the cutting edge of technology. This review analyzes the most recent synthetic approaches to this class of compounds

Syntheses and characterization of luminescente compounds containing 2,1,3-benzoxadiazole and 2,1,3 benzoxadiazole and thiophene based luminescente liquid crystals

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-graduação em Química, Florianópolis, 2013Esta tese é intitulada "Syntheses and Characterization of Luminescent Compounds Containing 2,1,3-Benzoxadiazole and 2,1,3-Benzothiadiazole and Thiophene Based Luminescent Liquid Crystals" apresenta a síntese e caracterização de duas séries de compostos. A primeira série consiste na preparação de compostos luminescentes p conjugados contendo os núcleos 2,1,3-benzoxadiazol e 2,1,3- benzotiadiazol como as unidades centrais aos quais os anéis aromáticos terminais, com números variáveis de cadeias alcóxi, estão ligados via ligações triplas (?C=C?). A síntese e caracterização estrutural é descrita na seção A, juntamente com a discussão dos resultados obtidos a partir das análises ópticas e eletroquímicas. Estes compostos mostraram uma fluorescência verde amarelada intensa com rendimentos quânticos relativos (Ff) de 27 a 32% em suas soluções em CHCl3. A natureza do heterociclo e comprimento das cadeias alcóxi diretamente ligadas a este mostraram pequena influência tanto na absorção quanto na emissão. No entanto, o número de cadeias alcóxi terminais ligadas aos anéis aromáticos apresentaram um efeito moderado sobre o comportamento da absorção. Os deslocamentos de Stokes foram razoavelmente elevados, com valores entre 95-107 nm, e com apenas uma pequena região de sobreposta entre a absorção e emissão. As medidas eletroquímicas apresentaram um pico de oxidação e um de redução em ciclos anódico e catódico, respectivamente. Os níveis de energia dos orbitais HOMO e do LUMO foram avaliados a partir dados voltamétricos e os cálculos mostraram que estes compostos possuem pequenos deslocamentos de bandas de energia, entre 1,91 e 2,57 eV.A segunda série de compostos é descrita na seção B. Estes compostos possuem estruturas moleculares curvadas devido à presença do tiofeno nos seus centros. Tal como na série anterior, estes compostos também possuem alta conjugação e os anéis aromáticos terminais estão ligados ao tiofeno através de ligações triplas (?C=C?). Estes compostos foram planejados para apresentar propriedades líquido-cristalinas e luminescentes. Eles mostraram forte fluorescência azul com rendimentos quânticos (Ff) satisfatórios entre 26 e 56% em relação ao sulfato de quinina. Alguns dos compostos da presente série apresentaram mesomorfismo. Os resultados preliminares, sugerem um padrão geral de que o aumento do comprimento da parte rígida da molécula aumenta a tendência de apresentar uma mesofase. Outro fato que se pode observado a partir destes resultados, é de que um aumento no comprimento molecular também aumenta a estabilidade térmica das mesofases devido a uma maior rigidez, o que facilita uma melhor orientação e ordenamento molecular nas mesofases. 2013-12-05T23:11:24

Shine bright or live long: substituent effects in [Cu(N^N)(P^P)]+-based light-emitting electrochemical cells where N^N is a 6-substituted 2,2'-bipyridine

We report [Cu(P^P)(N^N)][PF6] complexes with P^P = bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) and N^N = 6-methyl-2,2′-bipyridine (Mebpy), 6-ethyl-2,2′-bipyridine (Etbpy), 6,6′-dimethyl-2,2′-bipyridine (Me2bpy) or 6-phenyl-2,2′-bipyridine (Phbpy). The crystal structures of [Cu(POP)(Phbpy)][PF6]·Et2O, [Cu(POP)(Etbpy)][PF6]·Et2O, [Cu(xantphos)(Me2bpy)][PF6], [Cu(xantphos)(Mebpy)][PF6]·CH2Cl2·0.4Et2O, [Cu(xantphos)(Etbpy)][PF6]·CH2Cl2·1.5H2O and [Cu(xantphos)(Phbpy)][PF6] are described; each copper(I) centre is distorted tetrahedral. In the crystallographically determined structures, the N^N domain in [Cu(xantphos)(Phbpy)]+ and [Cu(POP)(Phbpy)]+ is rotated ∼180° with respect to its orientation in [Cu(xantphos)(Mebpy)]+, [Cu(POP)(Etbpy)]+ and [Cu(xantphos)(Etbpy)]+; in each complex containing xantphos, the xanthene ‘bowl’ retains the same conformation in the solid-state structures. The two conformers resulting from the 180° rotation of the N^N ligand were optimized at the B3LYP-D3/(6-31G**+LANL2DZ) level and are close in energy for each complex. Variable temperature NMR spectroscopy evidences the presence of two conformers of [Cu(xantphos)(Phbpy)]+ in solution which are related by inversion of the xanthene unit. The complexes exhibit MLCT absorption bands in the range 378 to 388 nm, and excitation into each MLCT band leads to yellow emissions. Photoluminescence quantum yields (PLQYs) increase from solution to thin-film and powder; the highest PLQYs are observed for powdered [Cu(xantphos)(Mebpy)][PF6] (34%), [Cu(xantphos)(Etbpy)][PF6] (37%) and [Cu(xantphos)(Me2bpy)][PF6] (37%) with lifetimes of 9.6–11 μs. Density functional theory calculations predict that the emitting triplet (T1) involves an electron transfer from the Cu–P^P environment to the N^N ligand and therefore shows a 3MLCT character. T1 is calculated to be ∼0.20 eV lower in energy than the first singlet excited state (S1). The [Cu(P^P)(N^N)][PF6] ionic transition-metal (iTMC) complexes were tested in light-emitting electrochemical cells (LECs). Turn-on times are fast, and the LEC with [Cu(xantphos)(Me2bpy)][PF6] achieves a maximum efficacy of 3.0 cd A−1 (luminance = 145 cd m−2) with a lifetime of 1 h; on going to the [Cu(xantphos)(Mebpy)][PF6]-based LEC, the lifetime exceeds 15 h but at the expense of the efficacy (1.9 cd A−1). The lifetimes of LECs containing [Cu(xantphos)(Etbpy)][PF6] and [Cu(POP)(Etbpy)][PF6] exceed 40 and 80 h respectively

Beyond Traditional Superatom Ligands and Cores

This dissertation summarizes my research in the Roy group on the development, synthesis, and study of new N-heterocyclic carbene (NHC) based ligands and nickel phsophinidene core compositions of molecular clusters, also known as superatoms. Chapter 1 introduces superatoms as atomically precise and discreet building blocks for use in the design and synthesis of novel materials. A brief history as well as selected synthetic strategies of superatoms will be introduced. The relevant materials properties of superatoms as well as their dependence on core composition and ligand structure will be discussed. Next, the use of superatoms with specialized or functionalizable ligands to synthesize new materials will be demonstrated. This chapter details the importance of the superatom ligands and core composition is the foundation that the subsequent chapters builds upon in developing these two areas. Chapter 2 introduces a functionalized NHC as a potential superatom ligand. While not necessary for all superatom ligands, ligands that enable electronic access to the superatom core are attractive. In this chapter, the conductance of potential NHC based ligands are probed through the scanning tunneling microscope-based break-junction (STM-BJ) method. A novel method of forming single molecule junctions in situ was used and these ligands are found to display a length dependent conductance with strong coupling to the Au electrode, confirming their potential use as ligands for superatoms. Chapter 3 describes the nature of the NHC–M bond in self-assembled monolayers (SAMs) on a Au(111) surface using high-resolution spectroscopy and theoretical calculations. This study was performed as a result of challenges and questions encountered during the work of Chapter 2. The results obtained from this study explore an important structure-function relationship of NHC ligands and have broader impact in materials chemistry beyond superatoms. Chapter 4 explores the synthesis of superatoms with NHC ligands beyond simple imidazolium-based NHCs. This chapter describes the two primary synthetic techniques used and the synthesis of NHC-ligated superatoms. This work is also ongoing and characterization is limited to crude single crystal X-ray diffraction structures and select NMRs. Finally, Chapter 5 details the use of uncommon organocyclophosphine reagents to synthesis novel nickel-phosphinidene molecular clusters, a potential new superatom. In this chapter the synthesis of a family of nickel-phosphinidene molecular clusters is described and studied. A potential application of these molecular clusters is explored through the thermolytic conversion to the industrially relevant Ni2P

Flexibility in metal–organic frameworks : a basic understanding

Much has been written about the fundamental aspects of the metal-organic frameworks (MOFs). Still, details concerning the MOFs with structural flexibility are not comprehensively understood. However, a dramatic increase in research activities concerning rigid MOFs over the years has brought deeper levels of understanding for their properties and applications. Nonetheless, robustness and flexibility of such smart frameworks are intriguing for different research areas such as catalysis, adsorption, etc. This manuscript overviews the different aspects of framework flexibility. The review has touched lightly on several ideas and proposals, which have been demonstrated within the selected examples to provide a logical basis to obtain a fundamental understanding of their synthesis and behavior to external stimuli

Carbene

Carbenes are important molecules in chemistry because of their photochemistry and high reactivity. They have many potential applications in medicinal and materials chemistry. This book provides a comprehensive introduction to carbenes and discusses their characteristics, structure, and synthesis procedures. It gives special emphasis to N-heterocyclic carbenes (NHCs) and their metal complexes

A Newly Synthesized β-amino-α, β-unsaturated Ketone Derivative of β-himachalene: Structural, NBO, NLO, and Molecular Docking Studies

In the current study, a new β-amino-α,β-unsaturated ketone-based himachalene ((1S,3R,8R)-9-amino-2,2-dichloro-3,7,7,10-tetramethyltricyclo[6.4.0.01,3]dodec-9-en-11-one) (4) was synthesized from β-himachalene (1) extracted from essential oil of Atlas Cedar. The β-amino-α, β-unsaturated ketone product (4) was characterized by 1D NMR (1H, 13C) and 2D NMR (HSQC, COSY, NOESY), FTIR analysis, and single-crystal X-ray diffraction. The title compound, C16H23Cl2NO, crystallizes with two molecules in the asymmetric unit with similar conformations. One of the two molecules is characterized by chlorine and one-methyl position disorder. In the crystal, intermolecular N—H…O hydrogen bonds lead to forming a three-dimensional framework. In addition, the molecular structure of the title compound was examined by Hirshfeld topology analysis and Density Functional Theory (DFT) using B3LYP calculations at 6-311+G(d,p) level. The optimized structure parameters were compared with the experimental result, an excellent correlation between theoretical structures parameters and experimental values was found. The natural bond orbitals (NBO) analysis and the first-order hyperpolarizability were also performed. Moreover, two biological activities were examined for product 4 against Acetylcholinesterase and Cytochrome P450 3A4, which bind to similar fragments with molecular docking. We find good scores and binding affinity of our molecule to link to these two proteins.Cadi Ayyad UniversityChouaib Doukkali UniversityMohammed V Universit

Large stabilization effects by intramolecular Beryllium bonds in Ortho-Benzene derivatives

Intramolecular interactions are shown to be key for favoring a given structure in systems with a variety of conformers. In ortho-substituted benzene derivatives including a beryllium moiety, beryllium bonds provide very large stabilizations with respect to non-bound conformers and enthalpy differences above one hundred kJ·mol(−1) are found in the most favorable cases, especially if the newly formed rings are five or six-membered heterocycles. These values are in general significantly larger than hydrogen bonds in 1,2-dihidroxybenzene. Conformers stabilized by a beryllium bond exhibit the typical features of this non-covalent interaction, such as the presence of a bond critical point according to the topology of the electron density, positive Laplacian values, significant geometrical distortions and strong interaction energies between the donor and acceptor quantified by using the Natural Bond Orbital approach. An isodesmic reaction scheme is used as a tool to measure the strength of the beryllium bond in these systems in terms of isodesmic energies (analogous to binding energies), interaction energies and deformation energies. This approach shows that a huge amount of energy is spent on deforming the donor–acceptor pairs to form the new rings

Fluorescent Probes Based on Metal and Aggregation-Induced Emission Organic Molecule Complexes for Bioimaging and Sensing Applications

Metal-Organic Coordination polymer (MOCPs) is an emerging class of inorganic-organic porous hybrid materials with infinite coordination polymers (CPs) or metal-organic backbones (MOFs) formed by the interaction between metal ions and organic ligands and ligand functional groups. The molecular structure of the organic ligands composing MOCPs is rich in variation, while inorganic metal ions generally have good photoelectromagnetic properties. Therefore, MOCPs have diverse structural variations, adjustable pore size, high stability and controllable synthesis, and have received wide attention in gas storage, multiphase catalysis, chemical sensing and biological applications. Fluorescence properties are one of the most widely used techniques for bioimaging and sensing detection. However, conventional luminescent groups are usually affected by aggregation-induced quenching (ACQ) effects. Aggregation-induced luminescence molecules (AIEs) based on metal-organic coordination polymers combine the advantages of organic AIEs and transition metal centers to improve photophysical properties and therapeutic effects