Molecular Rods. 1. Simple Axial Rods

Schwab, Peter; Levin, Michael D; Michl, Josef

doi:10.1021/cr970070x

Cited by 547 publications

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“…The electron-transfer processes depend on molecular size and structure, as well as the temperature and the free-energy difference between the donor and acceptor in donor-bridge-acceptor systems. Currently, monodisperse and soluble -conjugated systems with a well-defined length and composition are receiving a growing interest for the design of molecular wires [4] and rods [5], since they can be used as tunable building blocks [6] for nanoscale chemi-*Address correspondence to these authors at the Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, C.P.…”

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confidence: 99%

Synthesis of Pyrene-Anthracene Conjugated Molecular Rods

Domínguez-Chávez¹,

Ortega²,

Martínez‐García³

2009

TOOCJ

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Fully conjugated pyrene-anthracene-based molecular rods were synthesized by the Horner-WadsworthEmmons reaction utilizing potassium tert-butoxide in dry THF. The synthesized rods, which have butylene groups as solubility spacers in the main chain, exhibited good solubility in polar solvents. The solutions of the synthesized pyrenecontaining molecular rods exhibited a blue shift in the UV-vis from the absorption maximum due to the presence of the pyrene group in comparison with the dialdehydes. The chemical structure and purity of the synthesized rods were confirmed by 1 H and 13 C NMR, FAB+, MALDI-TOF, electrospray mass spectra and elemental analysis.Keywords: Molecular rods, Horner-Wadsworth-Emmons, anthracene, pyrene.The presence of charge-transfer reaction centers in macromolecules depends on factors as the composition, the separation in the interchromophore, the overall dynamical and supramolecular reorganization, and the electronic coupling [1]. The synthesis of artificial charge-transfer model systems in which the introduction of simple molecular changes is used to control and tune the magnitude of the electrontransfer parameters became a theme of great interest in the last years. The molecular chains or bridges inside the molecule provide endless opportunities, since they determine the structural features and the size of the electronic coupling between the donor and acceptor fragments [2]. The modification of the spacer gives the possibility to introduce a systematic alteration of separation, orientation, and overlap without affecting the electronic nature of the donor-acceptor pair, for which the coupling is proportional to the overlap of their electronic clouds [3]. The electron-transfer processes depend on molecular size and structure, as well as the temperature and the free-energy difference between the donor and acceptor in donor-bridge-acceptor systems. Currently, monodisperse and soluble -conjugated systems with a well-defined length and composition are receiving a growing interest for the design of molecular wires [4] and rods [5], since they can be used as tunable building blocks [6] for nanoscale chemi-*Address correspondence to these authors at the Instituto de Química, Universidad Nacional Autónoma de México, Cd. Universitaria, Coyoacán, C.P. 04510, México D.F., México; E-mail: margar@servidor.unam.mx cal entities in molecular and supramolecular electronic and photonic devices [7]. In this context, the combination of anthracene and styrene with pyrene compounds could lead to systems with good response in the electron-transfer processes [8].In the present work, we describe the synthesis of a new series of compounds in which pyrene is linked to a vinyl anthracene and oligo(phenylvinylene)anthracene. These conjugated block oligomers with well defined structure and donor-bridge array were synthesized by Heck and HornerWadsworth-Emmons reactions using aromatic mono vinyl aldehydes, dialdehydes and diphosphonates as monomers. RESULTS AND DISCUSSIONThe synthesis of the monovinyl and divinyl...

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confidence: 99%

Synthesis of Pyrene-Anthracene Conjugated Molecular Rods

Domínguez-Chávez¹,

Ortega²,

Martínez‐García³

2009

TOOCJ

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“…Metal-containing macrocycles with high symmetry and precise architecture are a new class of promising supramolecules for future application in nanotechnology because of their exact shape and size, as well as magnetic, photophysical, and electrostatic properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In this article, we describe scanning tunneling microscopy (STM) studies of the self-assembled supramolecular metallacyclic rectangle, cyclobis[(1,8-bis(transPt(PEt 3 ) 2 )anthracene)(1,4Ј-bis(4-ethynylpyridyl)benzene](PF 6 ) 4 , (Fig.…”

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confidence: 99%

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Gong

Wan

Yuan

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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A self-assembled supramolecular metallacyclic rectangle was investigated with scanning tunneling microscopy on highly oriented pyrolytic graphite and Au(111) surfaces. The rectangles spontaneously adsorb on both surfaces and self-organize into well ordered adlayers. On highly oriented pyrolytic graphite, the long edge of the rectangle stands on the surface, forming a 2D molecular network. In contrast, the face of the rectangle lays flat on the Au(111) surface, forming linear chains. The structures and intramolecular features obtained through high-resolution scanning tunneling microscopy imaging are discussed.metallacyclic macrocycle ͉ scanning tunneling microscopy ͉ molecular adlayer ͉ molecular orientation S elf-organization (1) and self-assembly (2) are critical and necessary processes in all living organisms and are of ever increasing importance in chemistry and material science. These processes will play a critical role in the so-called ''bottom-up'' strategy of nanofabrication. Therefore, understanding the organization of molecules on solid surfaces is important, both from a fundamental and applied perspective, for the construction of surface molecular nanostructures and nanodevices (3-13). A self-organized molecular pattern with control of structure and derived concomitant function could provide promising materials for the construction of nanodevices that cannot be prepared by conventional microfabrication. The arrangement of adsorbed molecules onto a surface depends on both intermolecular and molecule-surface interactions. For example, Hipps and colleagues (3, 4) prepared a self-organized 2D bifunctional structure on a Au (111) Metal-containing macrocycles with high symmetry and precise architecture are a new class of promising supramolecules for future application in nanotechnology because of their exact shape and size, as well as magnetic, photophysical, and electrostatic properties (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). In this article, we describe scanning tunneling microscopy (STM) studies of the self-assembled supramolecular metallacyclic rectangle, cyclobis [(1, ) 2 )anthracene)(1,4Ј-bis(4-ethynylpyridyl)benzene](PF 6 ) 4 , (Fig. 1) (28). The dimensions of a single rectangle molecule were independently determined to be 3.1 nm long by 1.2 nm wide, from the previously reported x-ray crystallographic data (28). The molecular adlayers were prepared on highly oriented pyrolytic graphite (HOPG) and Au(111) surfaces to investigate the effect of substrate on adlayer formation. The molecules self-organize into well ordered 2D adlayers on both surfaces, and high-resolution STM results clearly reveal an intact rectangle on both HOPG and Au (111) surfaces, but the symmetry and molecular orientation the molecules adopt depends on the substrate. Materials and MethodsChemicals. The PF 6 Ϫ salt of the rectangle was prepared analogously to the ClO 4 Ϫ salt previously reported (28), substituting KPF 6 for NaClO 4 .Substrates. HOPG (quality ZYB) was purchased from Digital Instruments (Santa Barbar...

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“…The use of organic rather than inorganic compounds to fabricate nanostructures usually has the advantage of higher luminescence efficiency at the same material density, more flexible spectroscopic properties, and in general easier and cheaper processing. Especially rod-like molecules [31,32] like oligothiophenes [27,33], perylenes [34,35], pentacenes [36] and oligo-p-phenylenes [37][38][39][40] have been studied in this context [41,42]. Among those the latter ones and especially the p-hexaphenylene has been found to form very interesting needle-like, parallely oriented nanoaggregates upon vapour deposition by a sophisticated high vacuum surface growth process [43,44].…”

Section: Fig 12mentioning

confidence: 99%

Organic Molecular Nanotechnology

Schiek

Balzer

Al‐Shamery

et al. 2008

Small

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Zur Homepage der Dissertation AbstractFormation of needle-like crystals from inorganic as well as from organic semiconductors such as para-phenylenes, α-thiophenes and phenyl-thiophene co-oligomers on dielectric surfaces has attracted increasing interest within the last years. The para-hexaphenylene has proven to be a versatile building block for generating long, parallely aligned organic nanofibers by a self-assembly process on a muscovite mica substrate via sublimation in high vacuum. These nanofibers possess outstanding optical properties like strong, polarised blue fluorescence in high quantum yields after unpolarised excitation with UV light, waveguiding and lasing features. Furthermore, they are chemically and thermically stable and can be easily detached from the growth substrate to serve as key elements in next generation optoelectronic and nanophotonic devices. Owing to their typical height and width on a nanometer scale and length up to one millimeter, the fibers bridge the gap between microscopic and macroscopic dimensions. The morphology of the nanofibers (length, height, width, aspect ratio, bending into rings) is susceptable to process parameters and pretreatment of the substrate. But chemically functionalisation of the molecular building block as key step of this thesis widens the scope of possibilities: Nanoaggregates with tailored morphology and optical properties are generated from designed functionalised molecular building blocks. Functional groups have been implemented at the 1,4´´´-para-positions of p-quaterphenylenes using a non-trivial Suzuki cross-coupling strategy. Symmetrically as well as non-symmetrically functionalised oligomers have been achieved in excellent yields and high purity. Additionally, the synthesis of phenyl-thiophene cooligomers and their acceptability for the nanofiber growth on muscovite mica via organic molecule deposition in high vacuum are presented. The fluorescence peak emission frequency of the nanostructures from the substituted p-quaterphenylenes shifts within the blue depending on the functionalisation. While dimensions are still influenced by the growth parameters, the overall shape (i.e. cross-section) of the aggregates alters significantly with the functional group. Even new properties like nonlinear optical activity are accessible. Due to intrinsic nonzero hyperpolarisability of push-pull functionalised oligomers, the respective nanofibers act as frequency doublers and emit strong second harmonic light after excitation with near infrared femtosecond laser pulses. Note that this design approach is possible while conserving the concept of highly crystalline nanofibers. Thus, a new route of bottom-up nanotechnology is presented starting from organic molecular synthesis towards generating of tailormade organic nanofibers opening new prospects for future nanotechnology. 3 ZusammenfassungDie Bildung von nadelförmigen Kristallen aus anorganischen und organischen Halbleitermolekülen wie zum Beispiel para-Phenylenen, α-Thiophenen und Phenylthiophen Co-oligomeren fa...

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Molecular Rods. 1. Simple Axial Rods

Cited by 547 publications

References 531 publications

Synthesis of Pyrene-Anthracene Conjugated Molecular Rods

Synthesis of Pyrene-Anthracene Conjugated Molecular Rods

Mesoscopic self-organization of a self-assembled supramolecular rectangle on highly oriented pyrolytic graphite and Au(111) surfaces

Organic Molecular Nanotechnology

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