Enhancing exciton diffusion in porphyrin thin films using peripheral carboalkoxy groups to influence molecular assembly

Kaushal, Meesha; Ortiz, Angy L.; Kassel, Jennifer A.; Hall, Nikolas; Lee, Taesoo D.; Singh, Gaurav; Walter, Michael G.

doi:10.1039/c6tc01741j

Cited by 18 publications

(13 citation statements)

References 59 publications

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“…This branching is likely why ZnTCEH 4 PP does not have strong quenching efficiency. Surprisingly, the 2-ethylhexyl free-base derivative exhibited a sharp Bragg peak at 2θ = 5.78° in the earlier study [ 19 ]. The absence of a Bragg peak in the metalloporphyrin could also be a result of the addition of the Zn (II) ion and the molecular shape-induced effects thereof.…”

Section: Discussionmentioning

confidence: 79%

“…The ZnTCEH 4 PP thin film also showed the highest S 0 –S 1 with the most prominent Q 4 band among the four derivatives. The shifts and broadening of the Soret peaks could be attributed to various alkyl chain-dependent orientations that the Zn porphyrin molecules assemble in and the resultant π–π macrocyclic interactions [ 19 , 27 , 28 ]. The shift in spectra suggests that the peripheral alkyl chains modulate molecular transition dipole orientation and alignment in thin films and play a strong role in the electronic transitions of these materials.…”

Section: Resultsmentioning

confidence: 99%

“…The longest exciton diffusion length is observed for ZnTCO 4 PP, measuring at an astounding 80.67 nm. This is one of the highest exciton diffusion lengths observed in similar metalloporphyrin thin films and longer than the exciton diffusion length of its free-base counterpart by over three folds [ 19 ]. ZnTCO 4 PP also has an exciton diffusion coefficient which is one order above the other derivatives.…”

Section: Resultsmentioning

confidence: 99%

“…Our earlier studies demonstrated how varying peripheral alkyl groups on free-base (alkoxycarbonyl)phenylporphyrins would affect molecular assembly and energy diffusion in solution-cast thin films [ 19 ]. We established that peripheral alkyl groups govern molecular organization and reported exciton diffusion lengths of up to 25 nm.…”

Section: Introductionmentioning

confidence: 99%

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Self-Assembly-Directed Exciton Diffusion in Solution-Processable Metalloporphyrin Thin Films

Shibu¹,

Middleton²,

Kwiatkowski³

et al. 2021

Molecules

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The study of excited-state energy diffusion has had an important impact in the development and optimization of organic electronics. For instance, optimizing excited-state energy migration in the photoactive layer in an organic solar cell device has been shown to yield efficient solar energy conversion. Despite the crucial role that energy migration plays in molecular electronic device physics, there is still a great deal to be explored to establish how molecular orientation impacts energy diffusion mechanisms. In this work, we have synthesized a new library of solution-processable, Zn (alkoxycarbonyl)phenylporphyrins containing butyl (ZnTCB4PP), hexyl (ZnTCH4PP), 2-ethylhexyl (ZnTCEH4PP), and octyl (ZnTCO4PP) alkoxycarbonyl groups. We establish that, by varying the length of the peripheral alkyl chains on the metalloporphyrin macrocycle, preferential orientation and molecular self-assembly is observed in solution-processed thin films. The resultant arrangement of molecules consequently affects the electronic and photophysical characteristics of the metalloporphyrin thin films. The various molecular arrangements in the porphyrin thin films and their resultant impact were determined using UV-Vis absorption spectroscopy, steady-state and time-resolved fluorescence emission lifetimes, and X-ray diffraction in thin films. The films were doped with C60 quencher molecules and the change in fluorescence was measured to derive a relative quenching efficiency. Using emission decay, relative quenching efficiency, and dopant volume fraction as input, insights on exciton diffusion coefficient and exciton diffusion lengths were obtained from a Monte Carlo simulation. The octyl derivative (ZnTCO4PP) showed the strongest relative fluorescence quenching and, therefore, the highest exciton diffusion coefficient (5.29 × 10−3 cm2 s−1) and longest exciton diffusion length (~81 nm). The octyl derivative also showed the strongest out-of-plane stacking among the metalloporphyrins studied. This work demonstrates how molecular self-assembly can be used to modulate and direct exciton diffusion in solution-processable metalloporphyrin thin films engineered for optoelectronic and photonic applications.

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Section: Discussionmentioning

confidence: 79%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Self-Assembly-Directed Exciton Diffusion in Solution-Processable Metalloporphyrin Thin Films

Shibu¹,

Middleton²,

Kwiatkowski³

et al. 2021

Molecules

Self Cite

View full text Add to dashboard Cite

show abstract

“…On the other hand, disk‐shaped molecules and two‐dimensional nanomaterials have a number of unique features. For instance, they provide the efficient transport of energy with electrons and molecular excitons . Thus, they are appropriate for organic light‐harvesting systems.…”

Section: Introductionmentioning

confidence: 99%

Tip‐modified Raman tensor of a porphine molecule

Gazizov

Салахов

Kharintsev

2019

J Raman Spectroscopy

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It is well established that bringing a plasmonic tip into the proximity of a single molecule inevitably affects its state and vice versa. Due to the enhanced light–matter interaction, spectroscopic information on the molecule captured with tip‐enhanced Raman spectroscopy (TERS) can noticeably differ on that coming from standard far‐field Raman spectroscopy. In this work, we develop a theoretical approach for calculating Raman tensors of a single oblate molecule that takes near‐field depolarization effects into account. Generally speaking, a tip‐dressed molecule exhibits the modified polarizability and, therefore, the Raman tensors. It is reported that the TERS technique can be used to reconstruct Raman tensors of vibration modes of anisotropic single molecules. The symmetric and antisymmetric modes of the molecules nearby a plasmonic tip are enhanced differently. In order to unravel the Raman tensors, two near‐field depolarization factors are necessarily introduced for the oblate molecule. As an example, we consider a free base porphine molecule as a test molecule to demonstrate the enhancement of intensities of Raman bands assigned to different symmetries. Also, we demonstrate an experimental way how to measure the depolarization factors using an ensemble of randomly oriented molecules. We believe that our finding will be beneficial to the interpretation of TERS measurements of single molecules.

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Helix‐Sense‐Selective Polymerization of Achiral Monomers for the Preparation of Chiral Helical Polyacetylenes Showing Intense CPL in Solid Film State

Yang

Zhang

et al. 2022

Macromol. Rapid Commun.

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Polymer-based circularly polarized luminescent (CPL) materials have attracted ever-increasing interest. However, to construct CPL materials from achiral monomers is still a big challenge. Here, a series of chiral helical substituted polyacetylenes are prepared by helix-sense-selective polymerization (HSSP) of achiral acetylenic monomers (achiral monomer + fluorescent monomer). HSSPs are accomplished in a bi-solvent mixture consisting of chloroform and chiral 𝜶-pinene (chiral component). Chirality transfers from the chiral component to the helical copolymers during polymerization, thereby endowing the copolymers with helical chirality. The resulting copolymers are then fabricated into blend films which exhibit intense optical activity and CPL. The monomer ratio and the physical state of the copolymers have significant impacts on their chiroptical and CPL properties. The maximum luminescence dissymmetry factor of the blend films can be up to 1.3 × 10 −2 . The universality of the established strategy for exploring polymer-based CPL materials is demonstrated by using different achiral fluorescent monomers. The present work opens a novel alternative for developing CPL-active polymeric materials starting from achiral monomers.

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Enhancing exciton diffusion in porphyrin thin films using peripheral carboalkoxy groups to influence molecular assembly

Abstract: The effects of molecular arrangement and orientation on the singlet exciton diffusion properties of carboalkoxyphenylporphyrins were investigated in solution-cast thin films.

Cited by 18 publications

References 59 publications

Self-Assembly-Directed Exciton Diffusion in Solution-Processable Metalloporphyrin Thin Films

Self-Assembly-Directed Exciton Diffusion in Solution-Processable Metalloporphyrin Thin Films

Tip‐modified Raman tensor of a porphine molecule

Helix‐Sense‐Selective Polymerization of Achiral Monomers for the Preparation of Chiral Helical Polyacetylenes Showing Intense CPL in Solid Film State

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