Stępień Lab Research
Some of our favorite molecules – all made in our lab
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A sulfate dianion occupies the central cavity of a neutral naphthalimide-fused cyclo[8]pyrrole, held by an inward-facing array of eight pyrrolic NH donors. The resulting host–guest complex has an overall charge of −2 and visualizes the orthosteric binding that raises the first apparent pKa from 6.3 to 10.2, attenuating Brønsted acidity by nearly four orders of magnitude.
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Three fluorenyl radical centers form a triskelion with approximate C3 symmetry, in which antiferromagnetic interactions cannot all be satisfied simultaneously. The resulting spin-frustrated doublet lies only 0.14 kcal mol−1 below the quartet, while the twisted helicene arms provide unusual ambient stability and support five accessible redox states with strong near-infrared absorption.
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Four negatively curved zinc-porphyrin cyclotrimers and two C60 molecules assemble into a pseudotetrahedral node of the cubic UWr-2 framework. Complementary concave and convex surfaces stabilize the assembly through dispersion interactions and propagate the framework’s ctn topology.
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Neutral tetrafluorenofulvalene in its singlet state adopts a strongly twisted geometry and pronounced open-shell character, frustrating conventional π bonding across its central alkene bond. Competition between steric strain, benzenoid aromaticity, and spin pairing underlies its unusual response to changes in charge and spin state.
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The D4 zinc(II) complex adopts a configurationally stable propeller shape in which four naphthalenemonoimide units form helically twisted stereogenic elements around the porphyrin. Bulky 4-(tert-butyl)phenyl groups lock this configuration, enabling separation of persistent enantiomers of a π-extended chromophore absorbing in the near-infrared.
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This coronoid alternates Chichibabin- and Schlenk-type connections between six spin centers, producing a singlet ground state with pronounced hexaradical character and low-lying triplet, quintet, and septet states. Its nearly planar π system combines global paratropicity, an electronic gap of ca. 0.8 eV, and oxidation-induced near-infrared absorption extending beyond 3300 nm.
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The pliable, electron-rich cavity of the molecular squid folds around a dicationic PQ2+ guest to form a compact inclusion complex. This host–guest pair, also featured on the JACS cover, illustrates how the receptor adapts its shape to electron-poor aromatic guests.
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Two giant nanographenoid radicals recombine through an elongated C(sp3)–C(sp3) bond to form a conformationally locked, two-layer nanosandwich. Extensive overlap of the ruffled π surfaces provides strong dispersion stabilization, making the σ-dimer resistant to thermal cleavage but susceptible to light-induced dissociation.
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A 9,9′-bicarbazole unit twists a [16]cycloparaphenylene nanohoop into a strained molecular lemniscate. Its figure-eight shape creates a configurationally stable chiral π-system with curvature-dependent spectroscopic features, red-shifted fluorescence, and circularly polarized luminescence.
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An iodide ion occupies the central cavity of neutral [4]chrysaorene, a fully conjugated coronoid macrocycle with pronounced open-shell character. The structure visualizes the close coupling between anion recognition and the redox chemistry of its π-system.
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Six naphthalenemonoimide units radially extend the HPHAC core into a ruffled, electron-deficient nanographene containing 37 fused rings. The molecule combines strong fluorescence in its neutral state with exceptionally rich redox chemistry spanning at least 13 oxidation levels and intense near-infrared absorption in its charged states.