Tetracationic cyclophanes and their use in the sequestration of polyaromatic hydrocarbons by way of complexation
Inventors
Stoddart, J. Fraser • Barnes, Jonathan C. • Jurí{hacek over (c)}ek, Michal
Assignees
US Department of Energy • Northwestern University
Publication Number
US-9290495-B2
Publication Date
2016-03-22
Expiration Date
2033-12-20
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Abstract
Novel tetracationic cyclophanes incorporating π-electron poor organic compounds into their ring structures, as well as methods of making the cyclophanes, are provided. The cyclophanes are able to form electron donor-acceptor complexes with a variety of polyaromatic hydrocarbons (PAHs) ranging in size, shape, and electron density. Also provided are methods of using the cyclophanes in the sequestration of PAHs in liquid or gaseous samples, the separation of PAHs from liquid or gaseous samples, the detection of PAHs in liquid samples, and the exfoliation of graphene via pseudopolyrotaxane formation.
Core Innovation
The invention provides novel tetracationic cyclophanes incorporating π-electron poor organic compounds into their ring structures. These cyclophanes are capable of forming electron donor-acceptor inclusion complexes with a variety of polyaromatic hydrocarbons (PAHs) differing in size, shape, and electron density. The cyclophanes have a closed ring structure comprising two 4,4′-(1,4-phenylene)bispyridinium units and two p-phenylene units connected via four methylene bridges or two 4,4′-(4,4′-[n]phenylene)bispyridinium (n≥1) units and two p-phenylene units connected similarly. Their solubility can be tuned by selecting appropriate counterions to enable complexation in organic or aqueous media.
The cyclophanes form strong inclusion complexes with PAHs by fixed π-π stacking distances and increased charge-transfer interactions, where the π-electron poor units in the cyclophane sandwich the π-electron rich PAH guest inside the rigid cyclophane ring. This interaction allows for applications including sequestration, separation, and detection of PAHs, as well as exfoliation of graphene nanoribbons via pseudopolyrotaxane formation.
The problem addressed stems from the environmental and health hazards posed by PAHs, which are carcinogenic, mutagenic, and teratogenic compounds found as pollutants in soil, air, and water. Existing methods to sequester and detect PAHs often employ cyclodextrins or metalligand metallocycles, which can be expensive and involve heavy metals such as Pd and Pt, raising environmental and economic concerns. Thus, there is a need for effective, economical, and environmentally benign compounds to complex PAHs.
Claims Coverage
The patent includes four independent claims covering the cyclophanes of specific formulas and methods using these cyclophanes for PAH sequestration, separation, detection, and graphene exfoliation. The main inventive features encompass the chemical structure of the cyclophanes and their diverse functional uses.
Tetracationic cyclophanes of defined formula incorporating π-electron poor units
Cyclophanes characterized by formula I comprising two 4,4′-(1,4-phenylene)bispyridinium units and two p-phenylene units linked via four methylene bridges or two 4,4′-(4,4′-[n]phenylene)bispyridinium (n≥1) units and two p-phenylene units linked via four methylene bridges, with R substituents and counterions, capable of complexing PAHs.
Method for sequestering polyaromatic hydrocarbons using the cyclophanes
Mixing one or more cyclophanes of formula I with a sample containing polyaromatic hydrocarbons to form inclusion complexes, optionally removing these complexes from the sample and separating PAHs from cyclophanes. Applicable to organic liquids (e.g., crude oil), aqueous liquids (e.g., drinking or natural water), or vapor phase samples (e.g., exhaust streams, cigarette smoke).
Chromatographic separation of polyaromatic hydrocarbons using immobilized cyclophanes
Passing a sample comprising multiple types of polyaromatic hydrocarbons over a solid support with immobilized cyclophanes of formula I, enabling reversible electron donor-acceptor interaction-based separation of different PAHs as they flow over the support.
Methods for detecting polyaromatic hydrocarbons and exfoliating graphene nanoribbons using cyclophanes
Detecting PAHs by mixing cyclophanes with a sample to form inclusion complexes that produce a visible color change, and monitoring the change. Exfoliating graphene nanoribbons from multi-layered stacks by exposing the stack to cyclophane solution, forming polypseudorotaxanes that exfoliate nanoribbons via Coulombic repulsion; exposure can be during nanoribbon synthesis or by solution agitation.
The independent claims define the chemical structures of tetracationic cyclophanes and provide methods employing these cyclophanes for sequestration, separation, detection of polyaromatic hydrocarbons, and exfoliation of graphene nanoribbons, highlighting their multifunctional utility based on electron donor-acceptor complex formation.
Stated Advantages
The cyclophanes exhibit particularly strong affinity and high binding constants for various PAHs due to fixed π-π stacking distances and charge-transfer interactions.
Solubility of the cyclophanes can be tuned via counterion selection, enabling their use in both organic and aqueous media.
They enable effective sequestration of PAHs from complex mixtures such as crude oil and environmental samples.
Visual detection of PAHs is possible through a visible color change upon complex formation with the cyclophanes.
The cyclophanes facilitate the chromatographic separation of different PAHs through reversible and selective electron donor-acceptor interactions.
They allow exfoliation of stacked graphene nanoribbons into individual sheets by Coulombic repulsion via formation of polypseudorotaxanes.
Documented Applications
Sequestration of polyaromatic hydrocarbons from liquid or vapor phase samples including crude oil, drinking water, natural waters, vehicle exhaust, cigarette smoke, and industrial exhaust.
Chromatographic separation of mixtures of different polyaromatic hydrocarbons in organic or aqueous samples by using solid supports with immobilized cyclophanes.
Detection of polyaromatic hydrocarbons in solution by inducing detectable visible color changes when complexed with cyclophanes.
Exfoliation of individual graphene nanoribbons from multi-layered stacked graphene nanoribbons via formation of polypseudorotaxanes with cyclophanes and subsequent Coulombic repulsion.
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