Tetraaryltetrabenzoporphyrins (TATBPs) show, due to their optoelectronic properties, rising potential as dyes in various fields of physical and biomedical sciences. However, unlike in the case of porphyrins, the potential structural diversity of TATBPs has been explored only to little extent, owed mainly to synthetic hurdles. Herein, we prepared a comprehensive library of 30 TATBPs and investigated their fundamental properties. We elucidated structural properties by X‐ray crystallography and found explanations for physical properties such as solubility. Fundamental electronic aspects were studied by optical spectroscopy as well as by electrochemistry and brought in context to the stability of the molecules. Finally, we were able to develop a universal synthetic protocol, utilizing a readily established isoindole synthon, which gives TATBPs in high yields, regardless of the nature of the used arylaldehyde and without meticulous chromatographic purifications steps. This work serves as point of orientation for scientists, that aim to utilize these molecules in materials, nanotechnological, and biomedical applications.
Within the past decade,
tetraaryltetrabenzoporphyrins (TATBPs)
have gained rising attention due to their potential in various fields
of materials science and medicinal chemistry. However, this class
of compounds still lacks in structural diversity, especially in the
case of low-symmetrical compounds. Herein, mixed condensations were
utilized to generate TATBPs with different substituents either in
the meso-positions or the periphery of the macrocycle
with total yields of 55–58%. The separation of crude mixtures
was achieved by feasible chromatographic purification. The influence
of symmetry on the electronic properties of TATBPs was studied by
optical spectroscopy, electrochemistry, and X-ray diffraction.
Geodesic nitrogen‐containing graphene fragments are interesting candidates for various material applications, but the available synthetic protocols, which need to overcome intrinsic strain energy during the formation of the bowl‐shaped skeletons, are often incompatible with heteroatom‐embedded structures. Through this mass spectrometry‐based gas‐phase study, we show by means of collision‐induced dissociation experiments and supported by density functional theory calculations, the first evidence for the formation of a porphyrin‐embedded conical nanocarbon. The influences of metalation and functionalization of the used tetrabenzoporphyrins have been investigated, which revealed different cyclization efficiencies, different ionization possibilities, and a variation of the dissociation pathway. Our results suggest a stepwise process for HF elimination from the fjord region, which supports a selective pathway towards bent nitrogen‐containing graphene fragments.
We investigated the
adsorption of 2H-5,10,15,20-tetracyanophenyl-tetrabenzoporphyrin
(2H-TCNPTBP) molecules on Cu(111) by scanning tunneling microscopy
in ultrahigh vacuum at room temperature. Three types of network structures
are observed to coexist on the surface. The first two, a porous Kagome
lattice and a porous quadratic structure, are stabilized by cyano–Cu–cyano
bonds with Cu adatoms; the third is a close-packed hexagonal network,
with much weaker intermolecular H-bonds and dipole–dipole interactions
of oppositely oriented cyano end groups. The coexistence of the three
structures is attributed to very similar energetics. While the two
metal-coordinated porous structures with identical molecular density
are stabilized by the energy gain due to the network formation, the
hexagonal network compensates the weaker intermolecular interactions
by a factor of 2.3 higher molecular density; furthermore, kinetic
stabilization might play a role. Our results show that cyano functionalization
of benzoporphyrins gives rise to unusual two-dimensional self-assembled
lattice structures.
Porphyrin‐based architectures have emerged as excellent candidates for artificial light‐harvesting antennae. Although tetrabenzoporphyrins (TBPs), the π‐extended “bigger brothers” of porphyrins, benefit from increased absorptivity in the near‐infrared (NIR), their utilization in light‐harvesting systems is still in its infancy. Within this work, we prepared two donor‐acceptor hetero dyads consisting of hexa‐peri‐hexabenzocoronenes (HBCs) to harvest high energetic near‐UV light, and a TBP core, which serves as visible to NIR light antenna and as subsequent energy sink of the conjugate. The HBCs are either attached to the meso‐position or via a maleimide‐bridge on the periphery of the macrocycle. Upon excitation of the HBC moieties, both dyads exhibit an efficient energy transfer to the TBP core. Furthermore, the TBP‐HBC dyads show superior light‐harvesting properties compared to the respective HBC‐porphyrin reference and the naturally occurring chlorophylls a/b.
We have recently succeeded in generating and detecting neutral cadmium clusters Cd, (x < 80) in a seeded supersonic molecular beam. The mass spectrometric abundances of photoionized clusters exhibit remarkable intensity variations. There are large intensity ratios for Cdlo/Cdll as well as Cd20/Cd21 indicating the closing of electronic shells with 20 and 40 electrons. The photoelectron spectra of neutral cadmium clusters show the formation and filling of shells, indeed. Discrete electronic states (2s') have been observed directly in the photoelectron spectra of mass specified Cdlo clusters. Pronounced electronic shell closings are also clearly observed for clusters with 70 electrons (Cd33, 92 electrons (Cd4&. and 138 electrons (Cd,,). Furthermore, we have obtained quantitative information on the size dependence of ionization potentials and photoionization cross sections. The ionization potentials (7.7 f 0.1 eV for the dimer Cd2 and 5.0 f 0.1 eV for Cd&) decrease rapidly but rather smoothly with increasing cluster size.
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