Search

Near‐Infrared (NIR) phosphorescence at room temperature is challenging to achieve for organic molecules due to negligible spin–orbit coupling and a low energy gap leading to fast non‐radiative transitions. Here, we show a supramolecular host–guest strategy to harvest the energy from the low‐lying triplet state of C64 nanographene tetraimide 1. 1H NMR and X‐ray analysis confirmed the 1 : 2 stoichiometric binding of a Pt(II) porphyrin on the two π‐surfaces of 1. While the free 1 does not show emission in the NIR, the host–guest complex solution shows NIR phosphorescence at 77 K. Further, between 860–1100 nm, room temperature NIR phosphorescence (λmax=900 nm, τavg=142 μs) was observed for a solid‐state sample drop‐casted from a preformed complex in solution. Theoretical calculations reveal a non‐zero spin–orbit coupling between isoenergetic S1 and T3 of π‐stacked [1 ⋅ Pt(II) porphyrin] complex. External heavy‐atom‐induced spin–orbit coupling along with rigidification and protection from oxygen in the solid‐state promotes both the intersystem crossing from the first excited singlet state into the triplet manifold and the NIR phosphorescence from the lowest triplet state of 1. [ABSTRACT FROM AUTHOR]

Phthalocyanines are extensively used by the dye and pigment industry and in photovoltaic and photodynamic therapy research due to their intense absorption of visible light, outstanding stability, and versatility. As pigments, the unsubstituted phthalocyanines are insoluble owing to strong intermolecular π‐π‐stacking interactions, which causes limitations for the solution chemistry for both free base and metalated phthalocyanines. Here we show a supramolecular host–guest strategy to dissolve phthalocyanines into solution. C64 nanographene tetraimide (1) binds two free base/zinc/copper phthalocyanines in a 1 : 2 stoichiometry to solubilize phthalocyanines as evidenced by 1H NMR spectroscopy, UV/Vis absorption and single‐crystal X‐ray analysis. Binding studies using a tetra‐tert‐butyl‐substituted soluble phthalocyanine revealed binding affinities of up to 109 M−1 in tetrachloromethane, relating to a Gibbs free energy of −52 kJ mol−1. Energy decomposition analysis revealed that complexes between 1 and phthalocyanines are stabilized by dispersion interactions followed by electrostatics as well as significant charge‐transfer interactions. [ABSTRACT FROM AUTHOR]

Enzymes actuate catalysis through a combination of transition state stabilization and ground state destabilization, inducing enantioselectivity through chiral binding sites. Here, we present a supramolecular model system which employs these basic principles to catalyze the enantiomerization of [5]helicene. Catalysis is hereby mediated not through a network of functional groups but through π‐π catalysis exerted from the curved aromatic framework of a chiral perylene bisimide (PBI) cyclophane offering a binding pocket that is intricately complementary with the enantiomerization transition structure. Although transition state stabilization originates simply from dispersion and electrostatic interactions, enantiomerization kinetics are accelerated by a factor of ca. 700 at 295 K. Comparison with the meso‐congener of the catalytically active cyclophane shows that upon configurational inversion in only one PBI moiety the catalytic effect is lost, highlighting the importance of precise transition structure recognition in supramolecular enzyme mimics. [ABSTRACT FROM AUTHOR]

Perylene bisimides (PBIs) are among the best fluorophores but have to be enwrapped for optoelectronic applications by large and heavy substituents to prevent their ππ‐stacking, which is known to accelerate non‐radiative decay processes in the solid state. Here, light‐weight di‐tert‐butylsilyl groups are introduced to bridge 1,12‐dihydroxy and 1,6,7,12‐tetrahydroxy PBIs to afford sublimable dyes for vacuum‐processed optoelectronic devices. For both new compounds, this substitution provides a twisted and shielded perylene π‐core whose, via OSiObridges, rigid structure affords well‐resolved absorption and emission spectra with strong fluorescence in solution, as well as in the solid state. The usefulness of these dyes for vacuum‐processed optoelectronic devices is demonstrated in organic light‐emitting diodes (OLEDs) that show monomer‐like emission spectra and high maximum external quantum efficiency (EQEmax) values of up to 3.1% for the doubly silicon‐bridged PBI. [ABSTRACT FROM AUTHOR]

A series of novel imide‐functionalized C64 nanographenes is investigated as acceptor components in organic solar cells (OSCs) in combination with donor polymer PM6. These electron‐poor molecules either prevail as a monomer or self‐assemble into dimers in the OSC active layer depending on the chosen imide substituents. This allows for the controlled stacking of electron‐poor and electron‐rich π–scaffolds to establish a novel class of non‐fullerene acceptor materials to tailor the bulk‐heterojunction morphology of the OSCs. The best performance is observed for derivatives that are able to self‐assemble into dimers, reaching power conversion efficiencies of up to 7.1%. [ABSTRACT FROM AUTHOR]

Herein we devise and execute a new synthesis of a pristine boron‐doped nanographene. Our target boron‐doped nanographene was designed based on DFT calculations to possess a low LUMO energy level and a narrow band gap derived from its precise geometry and B‐doping arrangement. Our synthesis of this target, a doubly B‐doped hexabenzopentacene (B2‐HBP), employs six net C−H borylations of an alkene, comprising consecutive hydroboration/electrophilic borylation/dehydrogenation and BBr3/AlCl3/2,6‐dichloropyridine‐mediated C−H borylation steps. As predicted by our calculations, B2‐HBP absorbs strongly in the visible region and emits in the NIR up to 1150 nm in o‐dichlorobenzene solutions. Furthermore, B2‐HBP possesses a very low LUMO level, showing two reversible reductions at −1.00 V and −1.17 V vs. Fc+/Fc. Our methodology is surprisingly selective despite its implementation of unfunctionalized precursors and offers a new approach to the synthesis of pristine B‐doped polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Utilizing Pd‐catalyzed [5+2] annulation a series of heptagon‐extended corannulenes could be synthesized from a borinic acid precursor furnished by C−H borylation strategy. Single‐crystal X‐ray analysis revealed the presence of two conformational enantiomers crystallizing in a racemic mixture. Through their embedded five‐ and seven‐membered rings these polycyclic aromatic hydrocarbons (PAHs) exhibit both negative and positive curvature and UV/Vis/NIR absorption spectroscopy as well as cyclic voltammetry experiments provided insights into the influence of larger flanking aromatic systems and electron‐donating substituents encompassing the heptagonal ring. Through [5+2] annulation of acenaphthylene an azulene‐containing PAH with intriguing optoelectronical properties including a very small bandgap and absorption over the whole visible spectrum could be obtained. Theoretical calculations were employed to elucidate the long‐wavelength absorption and aromaticity. [ABSTRACT FROM AUTHOR]

Two macrocyclic architectures comprising oligothiophene strands that connect the imide positions of a perylene bisimide (PBI) dye have been synthesized via a platinum‐mediated cross‐coupling strategy. The crystal structure of the double bridged PBI reveals all syn‐arranged thiophene units that completely enclose the planar PBI chromophore via a 12‐membered macrocycle. The target structures were characterized by steady‐state UV/Vis absorption, fluorescence and transient absorption spectroscopy, as well as cyclic and differential pulse voltammetry. Both donor–acceptor dyads show ultrafast Förster Resonance Energy Transfer and photoinduced electron transfer, thereby leading to extremely low fluorescence quantum yields even in the lowest polarity cyclohexane solvent. [ABSTRACT FROM AUTHOR]