A cycloparaphenylene-based molecular lemniscate (CPPL) was obtained in a short synthesis involving masked p-phenylene equivalents. The strained figure-eight geometry of CPPL is sustained by the incorporated 9,9'-bicarbazole subunit, which also acts as a stereogenic element. The shape of the distorted [16]cycloparaphenylene nanohoop embedded in CPPL is accurately approximated with a Booth lemniscate. The structure of CPPL, investigated using NMR and Raman spectroscopic methods, revealed strain-dependent features, consistent with the variable curvature of the ring. The electronic and optical properties of CPPL combine features more characteristic of smaller cycloparaphenylenes, such as a reduced optical bandgap, and red-shifted fluorescence. CPPL was resolved into enantiomers, which are configurationally stable and provide strong chiroptical responses, including circularly polarized luminescence.

The first example of a Y-shaped ferrocene quinoxaline derivative with a surprisingly high and stable second harmonic generation (SHG) response in composite polymeric films is reported. The interesting quadratic hyperpolarizability values of different substituted Y-shaped chromophores are also investigated in solution by the EFISH technique.

A series of new N-arylated ferrocenepyrazole structures, carrying different donor or acceptor substituents in the para position of the aryl ring has been synthesized by the Chan-Lam cross coupling reaction. The nonplanar geometric molecular structure of some of these chromophores together with their crystal packing was determined by X-ray diffraction and the HOMO and LUMO energy levels were evaluated by electrochemical and optical measurements and by DFT theoretical calculations. By the investigation of solvent effects and TD-DFT calculations the intense electronic absorption band at around 270-310 nm was confirmed to be an internal-charge-transfer (ICT) band, showing a significant red shift by increasing the electron withdrawing properties of the substituent on the para position of the aryl ring. TD-DFT calculations and EFISH measurements of the quadratic hyperpolarizability have shown that also the second order NLO response of these new ICT chromophores can be tuned by changing the nature of the substituent. Both theoretical µβ, β and experimental EFISH µβ 1907 and β 1907 values are significant, with a quite satisfactory correlation of the general trend of theoretical µβ and EFISH µβ 1907 values. The highest value of EFISH µβ 1907 (410 x 10 -48 esu) was measured for the chromophore carrying the strong electron withdrawing NO 2 group. KSK thanks to DST for Inspire fellowship (IF-110138). KSK and NP gratefully acknowledge SIF DST-VIT-FIST, VIT University, Vellore for providing NMR, Mass and IR data. MP thanks, Prof. for their extremely useful suggestions and comments.

Circularly polarized luminescence (CPL) and Raman optical activity (ROA) were observed in a single spectroscopic experiment for a purely organic molecule, an event that had so far been limited to lanthanide‐based complexes. The present observation was achieved for [16]cycloparaphenylene lemniscate, a double macrocycle constrained by a rigid 9,9′‐bicarbazole subunit, which introduces a chirality source and allows the molecule to be resolved into two configurationally stable enantiomers. Distortion of oligophenylene loops in this lemniscular structure produces a large magnetic transition dipole moment while maintaining the π‐conjugation‐induced enhancement of the Raman signal, causing the appearance of the CPL/ROA couple. A two‐photon mechanism is proposed to explain the population of the lowest‐energy excited electronic state prior to the simultaneous emission‐scattering event.

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