ABSTRACT
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 000â 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.
ABSTRACT
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 (KC8) 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.
ABSTRACT
We describe the synthesis as well as the electronic and photophysical characterization of novel N-heterotriangulene derivatives decorated with methoxycarbonyl- and methyl-sulfanyl-substituted dithiafulvenyl moieties. The association of these electron-rich compounds with fullerene C60 as electron acceptor was investigated by means of photophysical, voltammetric, and mass spectrometric methods and rationalized by DFT calculations. Importantly, light-induced interactions between the dithiafulvene-substituted N-heterotriangulene bearing methoxycarbonyl substituents with C60 leads to cooperative fluorescence. Quantitative Job plot analyses by means of fluorescence spectroscopy and voltammetry confirm a 1:1 association with binding constants in the order of 104 m-1 . Supportive results for the supramolecular assembly of both N-heterotriangulenes with C60 were obtained by ESI mass spectrometric investigations in the gas phase.
ABSTRACT
Invited for this month's cover are the collaborating groups at the Friedrich-Alexander University Erlangen-Nürnberg (FAU), Germany and at the Max-Planck-Institut für Kohlenforschung, Germany. The cover picture shows the symbiosis of quantum chemical theory and gas-phase collision experiment investigating the influence of the electronic state on stability of the radical cation ([M]+ . ) and protonated triangulene ([M+H]+ ). The dissociation of the radical cation requires less energy due to the formation of an energetically favored extended aromatic π-system. Read the full text of the article at 10.1002/cplu.201600416.
ABSTRACT
Electrospray ionisation of N-heterotriangulenes (i.e., dimethylmethylene-bridged triphenylamines) with up to three pyridyl groups at their periphery, produces the true radical cation ([M]+ . ) and the protonated molecule ([M+H]+ ) simultaneously. These ions are studied as model systems to illustrate the stability alternation of odd- versus even-electron ions in energy-dependent collision-induced dissociation (CID) experiments. All ions show the same fragmentation pattern, the consecutive loss of three methyl radicals (. CH3 ) from the dimethylmethylene bridges of the central triangulene core. [M]+ . ions dissociate at much lower collision energies than their [M+H]+ counterparts. The radical cation forms a singlet fragment with an extended aromatic system that is energetically favoured. Ab initio and density functional theory calculations support this interpretation and allow the assignment of the electronic structure of the fragment ions. Consecutive collision-induced dissociations provide a better match with theory when studied with an ion trap, rather than a linear quadrupole. This is attributed to the resonant nature of the excitation of intermediate ions.
ABSTRACT
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.
ABSTRACT
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.
