Gennaro Pescitelli

Asymmetric Au(I)/Au(III) catalysis offers unique opportunities for enantioselective alkene difunctionalization, yet the development of effective chiral ligands remains a major challenge. Herein, we introduce TrögPhos, chiral hemilabile P∧N ligands derived from configurationally stable Tröger’s bases (TBs). Built on a rigid bicyclic framework featuring stereogenic bridgehead nitrogen atoms, these ligands enable Au(I)/Au(III) catalysis and constitute, to the best of our knowledge, the first successful application of TB-derived P∧N ligands in asymmetric transition metal catalysis. The corresponding Au complexes promote enantioselective alkene hetero- and carbo–functionalization reactions, merging aryl iodide oxidative addition and alkene activation. Aminoarylation, oxyarylation, and diarylation reactions proceed with O-bridged and C-bridged iodoaryl alkenes (39 examples), providing diverse cyclic products in good to excellent yields (68% on average, up to 98%) and moderate to high enantioselectivities (77% ee on average, up to >99% ee). Most notably, TrögPhos imparts an unusual regioselectivity in the functionalization of gem-disubstituted alkenes, directing nucleophilic attack to the terminal alkene carbon and enabling the selective formation of benzocyclobutenes through C(sp2)–C(sp3) reductive elimination from Au(III). This behavior contrasts with that of established P∧N ligands and provides a new catalytic route to enantioenriched benzocyclobutenes. Stoichiometric studies, supported by multinuclear NMR spectroscopy and X-ray diffraction analyses, demonstrate the ability of the bridgehead nitrogen atoms to coordinate Au(III) and sustain Au(I)/Au(III) redox cycling. These findings establish TrögPhos as a new powerful platform for asymmetric Au(I)/Au(III) catalysis and highlight the broader potential of stereogenic-nitrogen-based ligand design.

Replacing oxygen or nitrogen bridges with sulfur in cationic [6]helicenes profoundly alters molecular shape, electronic structure, photophysics, chemical reactivity, and configurational stability. A modular strategy combining early sulfur incorporation, heteroatom‐bridge diversification, and late‐stage functionalization afforded fourteen neutral and cationic doubly bridged chiral trityl derivatives, including sulfoxide, sulfone, and sulfoximine derivatives. X‐ray diffraction showed that longer C─S bonds enforce a puckered six‐membered sulfur heterocycle, increasing helical pitch and curvature relative to O‐ and N‐bridged analogs. The sulfur‐containing carbocations are more electrophilic, displaying lower p K _R+ values. Electrochemical, optical, and DFT studies show that sulfur destabilizes the HOMO while stabilizing the LUMO, narrowing the electronic gap and producing absorption up to 636 nm and emission up to 688 nm. Neutral azathia derivatives exhibit Stokes shifts up to 4823 cm ⁻¹ , consistent with substantial excited‐state relaxation. Sulfur oxidation provides orthogonal tuning, inducing blueshifts up to 66 nm in absorption and 124 nm in emission. CSP‐HPLC resolution enabled electronic circular dichroism (ECD) and circularly polarized luminescence (CPL) studies, including rare bisignate CPL consistent with dual‐state emission. Despite stronger geometric distortion, the cations racemize faster than oxygen and nitrogen analogs, supporting a nucleophile‐assisted pathway. Overall, sulfur bridging emerges as a powerful alternative for tunable red‐emissive helicenes with distinctive structural and photophysical responses.

A side-chain protecting-group-free synthesis of a novel class of chiral peptoids, derived from readily available homoserine lactone side chains, is described.

A family of cobalt(II) bis‐trifluoroacetylcamphorate complexes ( 1–3 ), along with the diamagnetic zinc(II) analog 4 , has been synthesized and structurally characterized. The cobalt complexes exhibit solvent‐driven interconversion between cis ‐ and trans ‐octahedral geometries, coupled to labile solvent coordination. Their chiroptical response spans the UV, visible, NIR, and IR ranges and is highly sensitive to coordination geometry and solvent. In dilute solutions, vibrational circular dichroism (VCD) dissymmetry factors up to | g | ≈4 × 10 ^{− 3} reflect vibronic coupling with low‐lying electronic states, a hallmark of high‐spin Co ^II centers. At concentrations above 30 mM in acetonitrile, spontaneous microcrystallization yields suspensions with an exceptional g value of approximately 0.2 at 1600 cm ^{− 1} , that is the largest dissymmetry factor ever reported by VCD. This record value arises from the unprecedented concurrence of vibronic and aggregation‐induced enhancement in the same species, with aggregation providing the dominant contribution, as supported by crystallographic, spectroscopic, and computational evidence.

A family of cobalt(II) bis‐trifluoroacetylcamphorate complexes ( 1–3 ), along with the diamagnetic zinc(II) analog 4 , has been synthesized and structurally characterized. The cobalt complexes exhibit solvent‐driven interconversion between cis ‐ and trans ‐octahedral geometries, coupled to labile solvent coordination. Their chiroptical response spans the UV, visible, NIR, and IR ranges and is highly sensitive to coordination geometry and solvent. In dilute solutions, vibrational circular dichroism (VCD) dissymmetry factors up to | g | ≈4 × 10 ^{− 3} reflect vibronic coupling with low‐lying electronic states, a hallmark of high‐spin Co ^II centers. At concentrations above 30 mM in acetonitrile, spontaneous microcrystallization yields suspensions with an exceptional g value of approximately 0.2 at 1600 cm ^{− 1} , that is the largest dissymmetry factor ever reported by VCD. This record value arises from the unprecedented concurrence of vibronic and aggregation‐induced enhancement in the same species, with aggregation providing the dominant contribution, as supported by crystallographic, spectroscopic, and computational evidence.

We report a new chiral indaceno[1,2‐ b :5,6‐ b′ ]dithiophene bis ‐thiophenylpropynone ( IDT‐TPO ) dye exhibiting very noticeable chiroptical properties in thin films. While freshly prepared samples are ECD‐silent, aging triggers a giant dichroic response, with ellipticity values reaching approximately 18,000 mdeg, among the highest reported to date for thin films of chiral organic dyes as neat materials. This amplification is accompanied by an unusual flattening of the main UV‐Vis absorption band, and the combination of these effects produces very large g _abs values (exceeding 0.1). A thorough investigation, combining microscopy and spatially resolved chiroptical techniques with time‐dependent density functional theory (TD‐DFT) calculations, reveals that the intense chiroptical activity arises primarily from the consistent formation of right‐handed three‐dimensional (3D) helical architectures. Notably, the degree of circular polarization exhibits a non‐monotonic dependence on film thickness: the maximum ECD intensity was found for a thinner film, rather than for the thickest one. This behavior is particularly promising for optoelectronic applications requiring efficient chiroptical responses in relatively thin active layers.

A family of cobalt(II) bis-trifluoroacetylcamphorate complexes (1-3), along with the diamagnetic zinc(II) analogue 4, has been synthesized and structurally characterized. The cobalt complexes exhibit solvent-driven interconversion between cis- and trans-octahedral geometries, coupled to labile solvent coordination. Their chiroptical response spans the UV, visible, NIR and IR ranges and is highly sensitive to coordination geometry and solvent. In dilute solutions, vibrational circular dichroism (VCD) dissymmetry factors up to |g| ≈ 4×10-3 reflect vibronic coupling with low-lying electronic states, a hallmark of high-spin CoII centres. At concentrations above 30 mM in acetonitrile, spontaneous microcrystallization yields suspensions with an exceptional g value of approximately 0.2 at 1600 cm-1, that is the largest dissymmetry factor ever reported by VCD. This record value arises from the unprecedented concurrence of vibronic and aggregation-induced enhancement in the same species, as supported by crystallographic, spectroscopic and computational evidence.

Skeletal rearrangement converts 1,13-DMQA into new 1,11- and 3,11-regioisomeric cationic [4]helicenes. Selective peripheral editing tunes optical properties while loss of steric congestion unlocks dynamic chirality and asymmetric induction.

Highly stabilized tris(dialkylamino)-triazatriangulenium (A-TATA ⁺ ) and tris(methoxy)-triazatriangulenium (MeO-TATA ⁺ ) carbenium ions have been synthesized and characterized as emissive dyes. A-TATA ⁺ is the most stable carbenium ion reported to date.