skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Assembled triphenylamine bis -urea macrocycles: exploring photodriven electron transfer from host to guests
Absorption of electronic acceptors in the accessible channels of an assembled triphenylamine (TPA) bis -urea macrocycle 1 enabled the study of electron transfer from the walls of the TPA framework to the encapsulated guests. The TPA host is isoskeletal in all host–guest structures analyzed with guests 2,1,3-benzothiadiazole, 2,5-dichlorobenzoquinone and I 2 loading in single-crystal-to-single-crystal transformations. Analysis of the crystal structures highlights how the spatial proximity and orientation of the TPA host and the entrapped guests influence their resulting photophysical properties and allow direct comparison of the different donor–acceptor complexes. Diffuse reflectance spectroscopy shows that upon complex formation 1·2,5-dichlorobenzoquinone exhibits a charge transfer (CT) transition. Whereas, the 1·2,1,3-benzothiadiazole complex undergoes a photoinduced electron transfer (PET) upon irradiation with 365 nm LEDs. The CT absorptions were also identified with the aid of time dependent density functional theory (TD-DFT) calculations. Cyclic voltammetry experiments show that 2,1,3-benzothiadiazole undergoes reversible reduction within the host–guest complex. Moreover, the optical band gaps of the host 1·2,5-dichlorobenzoquinone (1.66 eV), and host 1·2,1,3-benzothiadiazole (2.15 eV) complexes are significantly smaller as compared to the free host 1 material (3.19 eV). Overall, understanding this supramolecular electron transfer strategy should pave the way towards designing lower band gap inclusion complexes.  more » « less
Award ID(s):
1904386 1955768
PAR ID:
10323108
Author(s) / Creator(s):
; ; ; ; ; ; ;
Date Published:
Journal Name:
Physical Chemistry Chemical Physics
Volume:
23
Issue:
41
ISSN:
1463-9076
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ; ; (, The Journal of Physical Chemistry C)
    Achieving tunable electrical conductivity in organic materials is a key challenge for the development of next-generation semiconductors. This study demonstrates a novel approach using triphenylamine (TPA) bis-urea macrocycles as supramolecular hosts for guest-induced modulation of charge-transfer (CT) properties. By encapsulating guests with varying reduction potentials, including 2,5-dichloro-1,4-benzoquinone (ClBQ), 2,1,3-benzothiadiazole (BTD), and malononitrile (MN), we observed significant changes in the electrical conductivity. Crystals of the 1(ClBQ)0.31 complex exhibited an electrical conductivity of ∼2.08 × 10–5 S cm–1, a 10,000-fold enhancement compared to the pristine host. This is attributed to efficient CT observed in spectroscopic analyses and is consistent with the computed small HOMO–LUMO gap (2.92 eV) in a model of the host–guest system. 1(MN)0.39 and 1(BTD)0.5 demonstrated moderate conductivities explained by the interplay of electronic coupling, reorganization energy, and energy gap. Lower ratios of guest inclusion decreased the electrical conductivity by 10-fold in 1(ClBQ)0.18, while 1(MN)0.25 and 1(BTD)0.41 were nonconductive (10–9 S cm–1). This work highlights the potential of metal-free, porous organic systems as tunable semiconductors, offering a pathway to innovative applications in organic electronics. 
    more » « less
  2. ; ; ; ; ; (, European Journal of Organic Chemistry)
    Abstract A molecular rotor is created when a 2,1,3‐benzothiadiazole rotator is incorporated into a rigid arylene ethynylene framework supported by pyridine coordination to a metal (Ag+or PdCl2) guest. Comparisons to a similarly sized naphthyl rotator via1H NMR spectroscopy provide insights into the movement of these bicyclic rotators relative to the rigid stator framework. Chemical shift increases of 0.3 ppm, or more, upon metal complexation are consistent with through‐space interaction of the central arene with a bound PdCl2guest. Further study via X‐ray crystallography illustrates that rotation of the 2,1,3‐benzothiadiazole unit in the solid state is likely hampered by relatively strong chalcogen bonding (N⋅⋅⋅S distance of 2.93 Å), forming 2S‐2N squares between benzothiadiazoles of neighboring complexes. Strong π–π interactions (3.29–3.36 Å) between neighboring complexes likewise restrict solid‐state rotation of the potential benzothiadiazole rotator. Modest changes to UV–vis spectra upon metal coordination suggest that electronic properties are mostly independent of stator configuration. 
    more » « less
  3. ; ; ; (, Angewandte Chemie International Edition)
    Abstract We report the synthesis and X‐ray crystal structure of a cucurbituril–triptycene chimeric receptor (1). Host1binds to guests typical of CB[6]–CB[8], but also binds to larger guests such as blue box (20) and the Fujita square (22). Intriguingly, the geometries of the1⋅20and1⋅22complexes blur the lines between host and guest in that both components fulfill both roles within each complex. The fluorescence output of1is fully quenched by the formation of complexes with pyridinium‐derived guests. 
    more » « less
  4. ; ; ; ; ; (, The Journal of Physical Chemistry C)
    In this study, we combine experiments, calculated properties, and machine learning (ML) to design new triphenylamine-based (TPA) molecules that have a high photoinduced radical (PIR) generation in crystals. A dataset of 34 crystal structures was extracted from the Cambridge Crystallographic Data Centre. Eighteen structures with experimentally reported PIR values from 0 to 0.85% were used to build an ML model trained using Random Forest that achieves an average leave-one-out test set error of 0.173% PIR. The ML model was used to screen the remaining 16 compounds, of which 4 were selected and sub-sequently compared with the experimentally measured PIR%. The predicted PIR% demonstrated good agreement with the measured values of TPA bis-urea macrocycles host-guest complexes and non-macrocyclic compounds of TPAs. Examining a broad set of molecular architectures/scaffolds allows for investigating the structural and electronic properties that lead to high PIR generation. We found very different trends for macrocycles, linear TPAs, and mono TPAs, where mono TPAs consist-ently have the lowest PIR generation. Macrocycles tend to have the highest PIR generation, especially for systems with ben-zene and fluorobenzene guests. Although linear analogs overall perform worse than macrocycles, they display clear trends with increasing excited-state dipole moment, oscillator strength and electron-hole covariance, while decreasing ionization potential and interatomic distance are generally correlated with higher PIRs. What is consistently observed is that higher PIRs are seen for brominated analogs. Our study, therefore, provides guidelines for future design strategies of TPAs for PIR generation. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, Advanced Materials)
    Abstract Efficient heterogeneous photosensitizing materials require both large accessible surface areas and excitons of suitable energies and with well‐defined spin structures. Confinement of the tetracationic cyclophane (ExBox4+) within a nonporous anionic polystyrene sulfonate (PSS) matrix leads to a surface area increase of up to 225 m2g−1in ExBox•PSS. Efficient intersystem crossing is achieved by combining the spin‐orbit coupling associated to Br heavy atoms in 1,3,5,8‐tetrabromopyrene (TBP), and the photoinduced electron transfer in a TBP⊂ExBox4+supramolecular dyad. The TBP⊂ExBox4+complex displays a charge transfer band at 450 nm and an exciplex emission at 520 nm, indicating the formation of new mixed‐electronic states. The lowest triplet state (T1, 1.89 eV) is localized on the TBP and is close in energy with the charge separated state (CT, 2.14 eV). The homogeneous and heterogeneous photocatalytic activities of the TBP⊂ExBox4+, for the elimination of a sulfur mustard simulant, has proved to be significantly more efficient than TBP and ExBox+4, confirming the importance of the newly formed excited‐state manifold in TBP⊂ExBox4+for the population of the low‐lying T1state. The high stability, facile preparation, and high performance of the TBP⊂ExBox•PSS nanocomposites augur well for the future development of new supramolecular heterogeneous photosensitizers using host–guest chemistry. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email