A self-decoupled porphyrin with a tripodal anchor has been synthesized and deposited on Au(111) using different wet-chemistry methods. Nanoscale electroluminescence from single porphyrin molecules or aggregates on Au(111) has been realized by tunneling electron excitation. The molecular origin of the luminescence is established by the vibrationally resolved fluorescence spectra observed. The rigid tripodal anchor not only acts as a decoupling spacer but also controls the orientation of the molecule. Intense molecular electroluminescence can be obtained from the emission enhancement provided by a good coupling between the molecular transition dipole and the axial nanocavity plasmon. The unipolar performance of the electroluminescence from the designed tripodal molecule suggests that the porphyrin molecule is likely to be excited by the injection of hot electrons, and then the excited state decays radiatively through Franck-Condon π*-π transitions. These results open up a new route to generating electrically driven nanoscale light sources.

Vibronic coupling is a central issue in molecular spectroscopy. Here we investigate vibronic coupling within a single pentacene molecule in real space by imaging the spatial distribution of single-molecule electroluminescence via highly localized excitation of tunneling electrons in a controlled plasmonic junction. The observed two-spot orientation for certain vibronic-state imaging is found to be evidently different from the purely electronic 0–0 transition, rotated by 90°, which reflects the change in the transition dipole orientation from along the molecular short axis to the long axis. Such a change reveals the occurrence of strong vibronic coupling associated with a large Herzberg–Teller contribution, going beyond the conventional Franck–Condon picture. The emergence of large vibration-induced transition charges oscillating along the long axis is found to originate from the strong dynamic perturbation of the anti-symmetric vibration on those carbon atoms with large transition density populations during electronic transitions.

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For the endohedral fullerene molecule HoLu_{2}N@C_{80}, it is shown that the endohedral HoLu_{2}N unit may be oriented in a magnetic field. The Ho magnetic moment is fixed in the strong ligand field and aligns along the holmium-nitrogen axis. The torque of a magnetic field on the Ho magnetic moment leads to a hopping bias of the endohedral unit inclining to an orientation parallel to the externally applied field. This endohedral cluster distribution remains frozen below the onset of thermally induced rotation of the endohedral units. We derive an analytical statistical model for the description of the effect that scales below 7 T with the square of the external field strength, and that allows us to resolve the freezing temperature of the endohedral hopping motion. The freezing temperature is around 55 K and depends on the cooling rate, which in turn determines an activation energy for the hopping motion of 185 meV and a prefactor of 1.8×10^{14}  s^{-1}. For TbSc_{2}N@C_{80} we find the same behavior with a 3.5% higher freezing temperature.

role for the efficient intercavity coupling. However, the evanescent field is relatively weak in the reported photonic mole cules because most of the optical field is strongly confined within the coupled cavities (e.g., microdisks, [4,8,11,18] micro toroids, [19] microspheres, [3] microrods, [5,20] and microfibers [7] ). As such, one needs a deliberate control on both the cavity geometries and the intercavity coupling gap to ensure a good spectral match and efficient evanescent coupling between the coupled cavities. [18] Moreover, dynamic tuning of the intercavity coupling strength has been investigated in recent years, which were carried out by advanced and sophisticated techniques such as strain tuning, [21,22] acoustooptic control, [23] and precise micromanipulation techniques. [3] To extend and promote the research in the field of photonic molecules, it is of high interest to design novel photonic molecules extending from adjacent solid microcavities to thinwalled hollow cavities which possess intense evanescent field facilitating intercavity coupling and provide novel strategy for tuning of the coupling strength.Microtube cavities, which are formed by selfrolling of pre strained nanomembranes, feature unique properties such as hollowcore structures and ultrathin cavity walls (≈100-300 nm) for the study of lightmatter interactions and the integration of "labinatube" systems. [24][25][26][27] These key merits enable extensive applications ranging from optofluidic sensing, [28][29][30][31] single cell analysis, [32] dynamic molecular process detection, [33] photon plasmon coupling, [34] to optical spin-orbit coupling.[35] To combine with other media/objects, luminescent quantum dots, [36,37] quantum wells, [38] and organic molecules [39] have been enwrapped into the microtube wall by the rolling up process, which couple photoluminescence (PL) light to the microtube cavities to support whisperinggallery mode (WGM) resonances. [37,40] In this context, a design and demonstration of photonic molecule based on microtube cavity is of fundamental interest for the study of strong optical coupling and the promo tion of its potential applications.Herein, we report a novel design of photonic molecule by trapping a microsphere cavity into the hollow core of a rolled up microtube cavity. We focus on studying the WGM coupling between the trapped microsphere and microtube cavity with a significant difference of cavity sizes, which is in contrast to pre vious reports where the two externally adjacent microcavities possess highly similar sizes [11,12,41] or slightly mismatched sizes (less than two times). [4][5][6][7]18,[42][43][44] Periodic modulations on A photonic molecule formed by trapping a microsphere cavity into a hollow microtube cavity is demonstrated, which provides a novel design over conventional photonic molecules comprised of solid-core whispering gallery mode microcavities with externally tangent configuration. Periodic spectral modulations of mode intensity, resonant mode shift, and quality factor are observed...