Dipole-mediated exciton management strategy enabled by reticular chemistry

Abstract

Selectively blocking undesirable exciton transfer pathways is crucial for utilizing exciton conversion processes that involve participation of multiple chromophores. This is particularly challenging for solid-state systems, where the chromophores are...

Dipole-Dependent Waveguiding in an Anisotropic Metal–Organic Framework

“…Selected area electron diffraction (SAED) targeting the widest and lateral facets of the PyP-MOF microplates reveals that the microplates’ xy -plane host the pyrene ( TBAPy ) sheets, while the porphyrin pillars lie along the microplates’ z -axis (Figure d). As reported previously, cryogenic high-resolution transmission electron microscopy (cryo-HRTEM) micrographs capture a rectangular 2D lattice with parameters that match the dimensions of TBAPy tetra-coordinated to the zinc SBUs, corroborating the SAED data. Time-dependent density functional theory (TD-DFT) calculations suggest that the transition dipole of the lowest excited singlet state S 1 ( TBAPy ) lies within the pyrene ligand’s π-plane; while the effective dipole of S 1 ( Zn-P ) is along the N–N axis of the porphyrin ligand .…”

“…As reported previously, cryogenic high-resolution transmission electron microscopy (cryo-HRTEM) micrographs capture a rectangular 2D lattice with parameters that match the dimensions of TBAPy tetra-coordinated to the zinc SBUs, corroborating the SAED data. Time-dependent density functional theory (TD-DFT) calculations suggest that the transition dipole of the lowest excited singlet state S 1 ( TBAPy ) lies within the pyrene ligand’s π-plane; while the effective dipole of S 1 ( Zn-P ) is along the N–N axis of the porphyrin ligand . Thus, for the specific case of PyP-MOF , the transition dipoles of S 1 ( TBAPy ) and S 1 ( Zn-P ) are aligned parallel and perpendicular to the microplates’ widest facet, respectively (Figure d).…”

“…Based on comparisons with the PL of the ligand monomers (Figure S3), the higher-energy and lower-energy emissive states of PyP-MOF are assignable to S 1 ( TBAPy ) and S 1 ( Zn-P ), respectively. The dual-band emission in this material is enabled by an inhibited Förster resonance energy transfer (from pyrene to porphyrin) due to the perpendicular arrangement of the dipoles of the pyrene and the porphyrin moieties, as detailed in our previous work …”

“…The elongation of the diffraction spots results from diffuse scattering caused by the slight bending of this microplate strip. The data presented in (b, c, f, g) are reproduced from our previous work in ref and reproduced with permission from the Royal Society of Chemistry.…”

“…Other factors that can lead to the spike of waveguided pyrene PL at 77 K include reduced non-radiative decay and reduced re-absorption at lower temperatures. On the other hand, the quenching of the porphyrin singlet emission at 77 K can result from the reduced thermal fluctuation upon cooling, which imposes a more rigid perpendicular arrangement of the two chromophores’ dipoles and a stronger inhibition of the S 1 ( TBAPy ) → S 1 ( Zn-P ) energy transfer …”