Graphene-porphyrin nanohybrid materials with a direct covalent linkage between the graphene carbon network and the functional porphyrin unit have been successfully synthesized via a one-pot reductive diazotation approach. A graphite-potassium intercalation compound (KC) was dispersed in THF, and different isolated porphyrin-diazonium salts were added. The direct covalent binding and the detailed characterization of the functional hybrid material were carried out by Raman spectroscopy, TG-MS, UV/vis, and fluorescence spectroscopy. LDI-ToF mass spectrometry was introduced as a new versatile and sensitive tool to investigate covalently functionalized graphene derivatives and to establish the composition of the respective nanohybrid materials.
A free-base porphyrin carrying two hexabenzocoronene (HBC) substituents in a trans arrangement and its zinc complex have been prepared. The compounds were characterized extensively and found to form tricationic dimers in the gas phase. X-ray crystallography confirms for the zinc complex a profound π-stacking of the HBC moieties. In contrast, the free-base porphyrin incarcerates n-heptane which essentially prevents π-stacking. Upon excitation of the HBC substituents, efficient energy transfer to the central porphyrin is observed.
A feasible two-step synthesis and characterization of a full series of hexaarylbenzene (HAB) substituted porphyrins and tetrabenzoporphyrins is presented. Key steps represent the microwave-assisted porphyrin condensation and the statistical Diels-Alder reaction to the desired HAB-porphyrins. Regarding their applications, they proved to be easily accessible and effective high molecular mass calibrants for (MA)LDI mass spectrometry. The free-base and zinc(II) porphyrin systems, as well as the respective tetrabenzoporphyrins, demonstrate in solid state experiments strong red- and near-infrared-light emission and are potentially interesting for the application in "truly organic" light-emitting devices. Lastly, they represent facile precursors to large polycyclic aromatic hydrocarbon (PAH) substituted porphyrins. We prepared the first tetra-hexa-peri-hexabenzocoronene substituted porphyrin, which represents the largest prepared PAH-porphyrin conjugate to date.
A systematic series of superbenzene-porphyrin conjugates was synthesized and characterized. All conjugates show a high degree of cluster formation that correlates to the amount of tert-butylated hexa-peri-hexabenzocoronenes (tBuHBCs) attached to the porphyrin's periphery. Determined by mass spectrometry and X-ray diffraction, van der Waals (vdW) interactions like London dispersions (LD), stemming from solubilizing tert-butyl groups, were identified to be the major reason for the cluster formation. Cluster sizes comprised of more than twenty molecules with masses up to 70 000 Da were observed, which are rare examples of large architectures based on synthetic functional molecules, assembled by dispersion interactions. Novel strategies towards the design of solution processable functional materials, capable of dynamic transformations based on non-covalent synthesis can be envisioned.
We present a procedure for growing thin films of an organic polyamid material based on a cyclic repetition of two consecutive, complementary, self-limiting surface reactions. The molecular compounds that react with the surface are dissolved in an organic solvent. This new method exemplifies how atomic layer deposition (ALD) and molecular layer deposition (MLD) can benefit from being transferred from the gas phase to the liquid phase, given that a broad variety of advantageous reagents are only available in dissolved form. Atomic layer deposition (ALD) has established itself as a thin film deposition method with a broad range of applications, both in terms of functionalities and of materials.1,2 This technique is based on complementary, well-behaved gas-solid surface reactions with 'selflimiting' character. During ALD film growth, the chemical identity of the surface alternates between two distinct reactive states, so that a well-defined amount of material is deposited during each ALD cycle, independently of the amount of precursors delivered during each step. This feature renders ALD uniquely suited to coating structured substrates, including deep pores, with continuous films of homogeneous thickness.3 One very recent development of the ALD field has been the demonstration that the principles can be transferred from gaseous precursors to ones dissolved in liquid solvents, 4 generalizing a number of previously existing but more narrowly focused techniques such as electrochemical ALD (or underpotential deposition), layerby-layer (LBL) assembly of polyelectrolytes, and SILAR.5-12 Our previous paper demonstrates the principle of 'solution ALD' (sALD) and establishes reaction chemistry and procedures for the deposition of several inorganic oxides. The films obtained are comparable with corresponding 'gas-ALD' (gALD) layers not only in terms of growth rate and self-limiting behavior but also of the chemical identity and purity. The advantages of this novel deposition method are the mild (room-temperature) and experimentally facile (vacuum-free) reaction conditions, but also the wider range of potential precursors to be chosen from, since in sALD they do not have to be volatile.In this paper, we demonstrate this particular advantage of sALD toward a class of materials which has proven challenging in gALD so far, namely, organic polymer films. Of course, a number of studies have shown the successful deposition of organic or hybrid films by gALD, 13,14 but the so-called 'molecular layer deposition' has remained limited in scope due to the constraints that the small number of available volatile and reactive precursors represents. The difficulty becomes apparent if we consider a polyamide as an example (an important class since it includes biological as well as manufactured fibers such as silk, Nylon and Kevlar), Figure 1. Generating the amide bond between two monomers is possible upon reaction of an amine with an activated acyl unit (such as an acyl halide). However, a heterobifunctional precursor (such as an aminoacyl ha...
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