FUNCTIONAL CHROMOPHORES FOR LIGHT-HARVESTING APPLICATIONS

This doctoral thesis describes the design, synthesis and characterization as well as investigations of the optical properties of new functional chromophores. In the recent years, the term \u201cfunctional dyes\u201d used in a wild range of application areas, such as dyes for liquid crystals, lasers, displays, solar cells or bioimaging emphasize on the new functionality beyond color of \u3c0-conjugated chromophores.[1] In Chapter I a briefly insight into the general aspects of functional chromophores and emitters for light-harvesting, along with a concise outline of the manuscript is given to the reader. The preparation and physical characterization of oligo(p-phenylene vinylene)-derived single-walled carbon nanotubes (SWCNTs) conjugates are described in Chapter II. Moreover, further testing of functionalized SWCNTs as doping agents for spiro-OMeTAD in a flat CH3NH3PbI3-based solar cell was presented. Chapter III describes the synthesis of a novel class of O-doped polyaromatic hydrocarbons, in which two polyaromatic hydrocarbon substructures are bridged through one or two O atoms. This includes high-yielding ring-closure key steps that, depending on the reaction conditions, allow the formation of either furanyl or pyranyl structure through intramolecular C-O bond formation, and the stepwise planarization of oligonaphthalenes. X-ray single-crystal diffraction showed that the furanyl derivatives undergo \u3c0-\u3c0 stacking at the solid state. Photophysical measurements showed very nicely that the molecules feature high emission yield and tunable absorption UV-Vis properties. Finally, Chapter IV reports the preparation of a distinct category of \u3c0-conjugates, more in detail; a new family of bis-perylenol derivatives bearing different dihedral angles between the two perylene moieties was prepared and studied in terms of UV-Vis and emission spectroscopy. [1] a) Chen, Z.; Lohr, A.; Saha-M\uf6ller, C. R.; W\ufcrthner, F. Chem. Soc. Rev.2009, 38, 564\u2013584. b) Weil, T.; Vosch, T.; Hofkens, J.; Peneva, K.; M\ufcllen, K. Angew. Chemie - Int. Ed.2010, 49, 9068\u2013909

Leveraging fluorescent emission to unitary yield: dimerization of polycyclic aromatic hydrocarbons

We report on the synthesis and characterization of novel substituted 1,1′‐biperylene‐2,2′‐diols in which the dihedral angle between the two polycyclic aromatic hydrocarbon (PAH) units is tailored from ca. 60° to ca. 90° in the solid state by introduction of cyclo‐etheric straps or sterically hindered groups such as the triisopropylsilyl (TIPS) group. Depending on the type of substitution, we lock the dihedral angle between the perylenyl moieties enabling fine‐tuning of the molecular optoelectronic properties, with the molecules displaying the smallest angles acting as exceptionally strong emitters with unitary quantum yields

Tailored synthesis of N-substituted peri-Xanthenoxanthene Diimide (PXXDI) and Monoimide (PXXMI) Scaffolds

The tailored synthesis of homo (A2) and hetero (AB) N-substituted peri-xanthenoxanthene diimides (PXXDIs) and peri-functionalized PXX monoimides (PXXMIs) from 3-hydroxy naphthalic anhydride is described. As A2-type PXXDIs could be synthesized in one step, AB-type PXXDIs and PXXMIs were prepared through a modular approach capitalizing on sequential Suzuki coupling, imidation, and Pummerer reactions with very high yields. In view of their potential applications as organic semiconductors, self-organization studies were performed through liquid deposition on surfaces, depicting the formation of islands, needles, and rods

Experimental study of the structural effect on the nanosecond nonlinear optical response of O-doped polycyclic aromatic hydrocarbons (PAHs)

The nonlinear optical response of some O-doped PAHs is systematically investigated in the present work aiming to understand the influence of structural effects on their nonlinear optical response. In that view, the third-order nonlinear optical properties of these PAHs were measured under 4 ns, visible (532 nm) and infrared (1064 nm) laser excitation. The O-doped PAHs were found exhibiting large saturable absorption and negative sign nonlinear refraction under visible excitation, both increasing with the addition of naphtalene units and with the number of O-atoms. Their nonlinear optical response was found to be negligible under infrared excitation. Similar measurements performed on thin films of these PAHs have shown that they maintain their large nonlinear optical response even in solid state, confirming their high potential for opto-electronic and photonic applications

Tailoring colors by O-annulation of polycyclic aromatic hydrocarbons

The synthesis of O-doped polyaromatic hydrocarbons, in which two polycyclic aromatic hydrocarbon subunits are bridged through one or two O atoms, has been achieved. This includes high-yielding ring-closure key steps that, depending on the reaction conditions, yield the formation of either furanyl or pyranopyranyl linkages through intramolecular C-O bond formation. Comprehensive photophysical measurements in solution showed that these molecules feature exceptionally high emission yields and tunable absorption properties throughout the UV-vis spectral region. Electrochemical investigations showed that in all cases the O-annulation increases the electron donor capabilities by raising the HOMO energy level with the LUMO energy level being less affected. Moreover, third-order NLO measurements of solutions or thin films containing the dyes displayed very good second hyperpolarizibility values. Importantly, PMMA films containing the pyranopyranyl derivatives displayed weak linear absorption and NLO absorption compared to the nonlinearity and NLO refraction, respectively, revealing to be exceptional organic materials for photonic devices

Solvent Molding of Organic Morphologies Made of Supramolecular Chiral Polymers

12sihe self-assembly and self-organization behavior of uracil-conjugated enantiopure (R)- or (S)-1,1'-binaphthyl-2,2'-diol (BINOL) and a hydrophobic oligo(p-phenylene ethynylene) (OPE) chromophore exposing 2,6-di(acetylamino)pyridine termini are reported. Systematic spectroscopic (UVvis, CD, fluorescence, NMR, and SAXS) and microscopic studies (TEM and AFM) showed that BINOL and OPE compounds undergo triple H-bonding recognition, generating different organic nanostructures in solution. Depending on the solvophobic properties of the liquid media (toluene, CHCl3, CHCl3/CHX, and CHX/THF), spherical, rod-like, fibrous, and helical morphologies were obtained, with the latter being the only nanostructures expressing chirality at the microscopic level. SAXS analysis combined with molecular modeling simulations showed that the helical superstructures are composed of dimeric double-cable tape-like structures that, in turn, are supercoiled at the microscale. This behavior is interpreted as a consequence of an interplay among the degree of association of the H-bonded recognition, the vapor pressure of the solvent, and the solvophobic/solvophilic character of the supramolecular adducts in the different solutions under static and dynamic conditions, namely solvent evaporation conditions at room temperature.partially_openopenĐorđević, Luka; Marangoni, Tomas; Miletić, Tanja; Rubio-Magnieto, Jenifer; Mohanraj, John; Amenitsch, Heinz; Pasini, Dario; Liaros, Nikos; Couris, Stelios; Armaroli, Nicola; Surin, Mathieu; Bonifazi, DavideĐorđević, Luka; Marangoni, Tomas; Miletic, Tanja; Rubio Magnieto, Jenifer; Mohanraj, John; Amenitsch, Heinz; Pasini, Dario; Liaros, Nikos; Couris, Stelios; Armaroli, Nicola; Surin, Mathieu; Bonifazi, David

Orbital mapping of semiconducting perylenes on Cu(111)

Semiconducting O-doped polycyclic aromatic hydrocarbons constitute a class of molecules whose optoelectronic properties can be tailored by acting on the π-extension of the carbon-based frameworks and on the oxygen linkages. Although much is known about their photophysical and electrochemical properties in solution, their self-assembly interfacial behavior on solid substrates has remained unexplored so far. In this paper, we have focused our attention on the on-surface self-assembly of O-doped bi-perylene derivatives. Their ability to assemble in ordered networks on Cu(111) single-crystalline surfaces allowed a combination of structural, morphological, and spectroscopic studies. In particular, the exploitation of the orbital mapping methodology based on angle-resolved photoemission spectroscopy, with the support of scanning tunneling microscopy and low-energy electron diffraction, allowed the identification of both the electronic structure of the adsorbates and their geometric arrangement. Our multi-technique experimental investigation includes the structure determination from powder X-ray diffraction data for a specific compound and demonstrates that the electronic structure of such large molecular self-assembled networks can be studied using the reconstruction methods of molecular orbitals from photoemission data even in the presence of segregated chiral domains