The following information is provided to assist the reader in understanding technologies disclosed below and the environment in which such technologies may typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the technologies or the background thereof. The disclosure of all references cited herein are incorporated by reference.
During the last two decades the number of applications using carbon nanotubes (CNTs) have increased dramatically. CNTs have, for example, appeared as one fundamental material to advance the construction of nanocircuits. In principle, nanocircuits could be created where the conducting and semiconducting parts are made from CNTs alone. While their conductivity properties are highly desirable, control over CNTs synthesis is poor, which manifests in properties with high batch-to-batch variability. Also, CNTs conductivity is strictly determined from their chirality. Thus, for almost the same tube diameter, conductive and semiconductive CNTs are found. Tailored syntheses to produce a unique type of CNT is challenging and currently absent in the literature. Therefore, most procedures rely on separations from complex mixtures. In short, there is a pressing need for new synthetic methods to obtain analogues of CNTs.
In that regard, the next generation of molecular-scale electronic devices will require precise control of the building blocks' electronic properties. Homogeneity of the constituents and their properties may be achieved as long as molecules are utilized instead of dispersions. Thus, fundamental nanoscience research will likely focus on controlling the main component's properties via strict control of their synthesis.
However, synthesis of macromolecules in the nanosize regime with strict control of their molecular architecture remains a challenge in the synthetic community. Preparation of such macromolecules becomes even more difficult when such macromolecules include aromatic systems in strained geometries. As a result, overcoming the buildup of strain energy has to be carefully considered during their design process. CNTs are an example of inherently strained yet stable contorted aromatics.
Before the discovery of carbon nanotubes, belt-shaped fused aromatic compounds (see
Control over CNT growth has been partially accomplished by starting from preexisting units as briefly described above. These seeds usually involve 1) a short nanotube fragment, or 2) a nanotube end cap. The first method relies on cutting a preexisting isolated CNT into small pieces, treating and activating them to eventually use them as seeds for further CNT growth.
While this methodology has been reported to work successfully, it involves multiple challenging steps and the yield is rather low.
The second process uses thermally decomposed fullerenes as seeds. As described above, other similar alternatives utilize [n]cycloparaphenylenes or chemically synthesized hemispherical end caps (for example, C50H10). Proof-of-concept of the latter technique has been reported. However, the preparation of large quantities of such end caps is not a trivial undertaking.
Non-aromatic intermediates with sp3 carbon atoms have been used to facilitate establishing the overall connectivity before re-aromatizing the nanoring in the last step. Although this method has been successful, extending the nanoring along its main axis has proven challenging.
Thus, there remains a significant need to develop synthetic techniques to provide tubular systems/structures which may include strained aromatic species.
In one aspect, a method of creating a tubular compound includes providing an end cap including a macrocycle that is sufficiently rigid that it presents a plurality of functional groups oriented on or extending from a first axial side of the end cap, creating a tubular wall from a plurality of reactive compounds which is covalently attached to the end cap via reaction of the plurality of functional groups on the end cap extending from the first axial side thereof, the tubular wall extending axially from the first axial side of the end cap, and performing at least one equatorial cyclization reaction axially distant from the end cap which includes covalent bonding of residues of a group of the plurality of reactive compounds used in forming the tubular wall. In a number of embodiments, the macrocycle is generally cylindrical or ellipsoidal. The macrocyclic compound may, for example, include arene groups. In a number of embodiments, the plurality of functional groups on or extending from the first axial side of the macrocycle are hydroxy, alkoxy, halide or aldehyde groups. In a number of embodiments, the macrocycle is a resorcin[n]arene wherein n is an integer between 4 and 6, a bridged resorcin[n′]arene wherein n′ is an integer between 4 and 6, or a calix[n″]pyrrole-resorcinarene wherein n″ is an integer between 4 and 6.
In a number of embodiments, the plurality of reactive compounds is selected to maintain pi conjugation axially and equatorially in the tubular wall. In a number of embodiments, at least a portion of the plurality of reactive compounds include an arene group, an acene group, an N-heteroarene group or an N-heteroacene group. The tubular wall may, for example, include a plurality of acene groups, sections, or fragments or heteroatom-containing acene groups, sections, or fragments. Acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons made up of linearly fused benzene rings. Acenes, for example, have potential interest in optoelectronic applications. Additionally, conjugation in either direction, equatorial or axial, can be achieved by incorporation of acetylenic or alkynylene groups or fragments (—C≡C—) as well as alkenylene groups or fragments (—C═C—).
In a number of embodiments, the end cap includes a macrocyclic compound including arene groups and including the plurality of functional groups orients axially on or extending from the first axial side of the macrocycle and the method further includes reacting a first group of compounds of the plurality of reactive compounds with the macrocyclic compound to extend the macrocyclic compound in the axial direction. Each of the first group of compounds includes at least one functional group which is reactive with at least one of the plurality of functional groups of the macrocyclic compound extending from the first axial side thereof under a first set of reaction conditions. The first group of compounds of the plurality of reactive compounds further includes at least one of (i) at least other functional group which does not react with the plurality of functional groups of the macrocyclic compound extending from the first axial side thereof under the first set of reaction conditions and is oriented to react with one of a second group of compounds of the plurality of reactive compounds to axially extend the tubular wall, or (ii) two functional groups which do not react with the plurality of functional groups of the macrocyclic compound extending from the first axial side thereof under the first set of reaction conditions that are oriented to react to connect adjacent residues of the compounds of first group of compounds to form the at least one equatorial cyclization.
The compounds of the first group of compounds may, for example, include the at least one functional group to react with one of the compounds of the second group of compounds and two functional groups to connect adjacent residues of the compounds of first group of compounds to form the at least one equatorial cyclization. In a number of embodiments, after the compounds of the first group compounds are reacted with the macrocyclic compound, the method further includes reacting the second group of compounds with the residues of the first group of compounds to axially extend the tubular wall.
In a number of embodiments, the at least one equatorial cyclization reaction is an aryl-aryl coupling, a Suzuki-Miyaura cross coupling reaction to create a linkage including a phenylene group, a reaction to create a diimide linkage, or a reaction to create an alkynyl linkage. A plurality of equatorial cyclization reactions may, for example, be performed axially distant from the end cap.
The macrocycle may further include a second plurality of functional groups oriented axially on or extending from another or a second axial side of the end cap, opposite the first side. In a number of embodiments, the second plurality of functional groups are selected to control solubility, to participate in a polymerization reaction, or to attach the tubular compound to a substrate. In a number of embodiments, the macrocycle is:
wherein R′ is a hydroxy group or an alkoxy group, R″ is a halo group or an aldehyde group, R′″ is a halo group, a hydroxy group, an amine group, an aldehyde group, or a carboxylic group, and R is an alkyl group, an aryl group, an alcohol group, an amine group, a carboxyl group, an ether group, an olefinic group, or a hydrophilic polymer. In a number of embodiment R is a functional group suitable for reaction with another functional group on a substrate or R is a polymerizable group (for example, a polymerizable olefinic group, a hydroxy group, an amine group, or a carboxyl group). Protective groups may be used in connection with certain R groups during, for example, axial extension of the tubular compounds hereof.
In another aspect, a tubular compound is formed by a process including providing an end cap including a macrocycle that is sufficiently rigid that it presents a plurality of functional groups oriented axially on or extending from a first axial side of the end cap. creating a tubular wall from a plurality of reactive compounds which is covalently attached to the end cap via reaction of the plurality of functional groups extending from the first axial side of the end cap, the tubular wall extending axially from the end cap, and performing at least one equatorial cyclization reaction axially distant from the end cap which includes covalent bonding of residues of a group of the plurality of reactive compounds used in forming the tubular wall.
In a number of embodiments, the plurality of reactive compounds is selected to maintain pi conjugation axially and equatorially in the tubular wall. In a number of embodiments, at least a portion of the plurality of reactive compounds include an arene group, an acene group, an N-heteroarene group or an N-heteroacene group. The tubular wall may, for example, include a plurality of acene groups, sections, or fragments or heteroatom-containing acene groups, sections, or fragments. Acenes or polyacenes are a class of organic compounds and polycyclic aromatic hydrocarbons made up of linearly fused benzene rings. Acenes, for example, have potential interest in optoelectronic applications. Additionally, conjugation in either direction, equatorial or axial, can be achieved by incorporation of acetylenic or alkynylene groups or fragments or alkenylene groups or fragments.
As described above, in a number of embodiments, the end cap includes a macrocyclic compound including arene groups and including the plurality of functional groups oriented axially on or extending (axially) from a first axial side thereof, and the method further includes reacting a first group of compounds of the plurality of reactive compounds with the macrocyclic compound to extend the macrocyclic compound in the axial direction. Each of the first group of compounds includes at least one functional group which is reactive with at least one of the plurality of functional groups extending from the first axial of the macrocyclic compound under a first set of reaction conditions. The first group of compounds of the plurality of reactive compounds further includes at least one of (i) at least other functional group which does not react with the plurality of functional groups of extending from the first axial side of the macrocyclic compound under the first set of reaction conditions and is oriented to react with one of a second group of compounds of the plurality of reactive compounds to axially extend the tubular wall, or (ii) two functional groups which do not react with the plurality of functional groups of extending from the first axial side of the macrocyclic compound under the first set of reaction conditions that are oriented to react to connect adjacent residues of the compounds of first group of compounds to form the at least one equatorial cyclization.
The compounds of the first group of compounds may, for example, include the at least one functional group to react with one of the compounds of the second group of compounds and two functional groups to connect adjacent residues of the compounds of first group of compounds to form the at least one equatorial cyclization. In a number of embodiments, after the compounds of the first group compounds are reacted with the macrocyclic compound, the method further includes reacting the second group of compounds with the residues of the first group of compounds to axially extend the tubular wall.
In a number of embodiments, the at least one equatorial cyclization reaction is an aryl-aryl coupling, a Suzuki-Miyaura cross coupling reaction to create a linkage including a phenylene group, a reaction to create a diimide linkage, or a reaction to create an alkynyl linkage. A plurality of equatorial cyclization reactions may, for example, be performed axially distant from the end cap.
The macrocycle may further include a second plurality of functional groups oriented on another side or a second axial side of the end cap, opposite the first side. In a number of embodiments, the second plurality of functional groups are selected to control solubility, to participate a polymerization reaction, or to attach the tubular compound to a substrate. In a number of embodiments, the macrocycle is:
wherein R′, R″, R′″, and R are set forth above.
In a number of embodiments, the tubular compound has the formula:
In a further aspect, a structure for use in a separation, includes tubular residues of a tubular compound formed by a process including providing an end cap including a macrocycle that is sufficiently rigid that it presents a plurality of functional groups oriented axially on or extending (axially) from a first axial side of the end cap, the macrocycle further including a plurality of functional group oriented to extend from the second axial side of the end cap, opposite the first axial side, wherein reaction of one or more of the plurality of functional groups oriented to extend from the second axial side of the end cap covalently bonds the tubular residues of the tubular compounds within the structure, creating a tubular wall from a plurality of reactive compounds which is covalently attached to the end cap via reaction of the plurality of functional groups extending from the first axial side of the end cap, the tubular wall extending axially from the end cap, performing at least one equatorial cyclization reaction axially distant from the end cap which includes covalent bonding of residues of a group of the plurality of reactive compounds used in forming the tubular wall; and reacting one or more of the plurality of functional groups oriented to extend from the second axial side of the end cap to covalently bond the tubular residues of the tubular compounds within the structure.
The one or more of the plurality of functional groups oriented to extend from the second axial side of the end cap may, for example, be reacted with one or more functional groups of a substrate for the structure in forming the structure, or one or more of the plurality of functional groups oriented to extend from the second axial side of the end cap may, for example, be reacted in a polymerization reaction in forming the structure.
As described above, in a number of embodiments, the end cap includes a macrocyclic compound including arene groups and including the plurality of functional groups oriented axially on or extending from the first axial side thereof. A first group of compounds of the plurality of reactive compounds is reacted with the macrocyclic compound to extend the macrocyclic compound axially from the first axial side. Each of the first group of compounds includes at least one functional group which is reactive with at least one of the plurality of functional groups of macrocyclic compound extending from the first axial side thereof under a first set of reaction conditions. The first group of compounds of the plurality of reactive compounds further includes at least one of (i) at least other functional group which does not react with the plurality of functional groups of the macrocyclic compound extending from the first axial side thereof under the first set of reaction conditions and is oriented to react with one of a second group of compounds of the plurality of reactive compounds to axially extend the tubular wall, or (ii) two functional groups which do not react with the plurality of functional groups of the macrocyclic compound extending from the first axial side thereof under the first set of reaction conditions that are oriented to react to connect adjacent residues of the compounds of first group of compounds to form the at least one equatorial cyclization.
The compounds of the first group of compounds may, for example, include the at least one functional group to react with one of the compounds of the second group of compounds and two functional groups to connect adjacent residues of the compounds of first group of compounds to form the at least one equatorial cyclization. In a number of embodiments, after the compounds of the first group compounds are reacted with the macrocyclic compound, the method further includes reacting the second group of compounds with the residues of the first group of compounds to axially extend the tubular wall.
In a number of embodiments, the at least one equatorial cyclization reaction is an aryl-aryl coupling, a Suzuki-Miyaura cross coupling reaction to create a linkage including a phenylene group, a reaction to create a diimide linkage, or a reaction to create an alkynyl linkage. A plurality of equatorial cyclization reactions may, for example, be performed axially distant from the end cap.
One or more of the plurality of functional group oriented to extend from the second axial side of the end cap may, for example, be reacted with one or more functional groups of a substrate for the structure in forming the structure, or one or more of the plurality of functional group oriented to extend from the second axial side of the end cap may be reacted in a polymerization reaction in forming the structure.
In a number of embodiments, the macrocycle is:
wherein R′, R″, R′″, and R are set forth above.
The tubular residue of the tubular compound may, for example, selectively interact with at least one compound to be separated from a mixture of compounds. In a number of embodiments, the tubular residue of the tubular compound selectively interacts with at least one fullerene to be separated from a mixture of different fullerenes (for example, for separation of one of a C60 fullerene or a C70 fullerene from a mixture including both C60 and C70 fullerenes).
In a number of embodiments, the tubular compound has the formula:
The present devices, systems, methods, and compositions, along with the attributes and attendant advantages thereof, will best be appreciated and understood in view of the following detailed description taken in conjunction with the accompanying drawings.
It will be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations in addition to the described representative embodiments. Thus, the following more detailed description of the representative embodiments, as illustrated in the figures, is not intended to limit the scope of the embodiments, as claimed, but is merely illustrative of representative embodiments.
Reference throughout this specification to “one embodiment” or “an embodiment” (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” or the like in various places throughout this specification are not necessarily all referring to the same embodiment.
Furthermore, described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the various embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, et cetera. In other instances, well known structures, materials, or operations are not shown or described in detail to avoid obfuscation.
As used herein and in the appended claims, the singular forms “a,” “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a compound” includes a plurality of such compounds and equivalents thereof known to those skilled in the art, and so forth, and reference to “the compounds” is a reference to one or more such compounds and equivalents thereof known to those skilled in the art, and so forth. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, and each separate value, as well as intermediate ranges, are incorporated into the specification as if individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contraindicated by the text.
In a number of embodiments hereof, macrocycles are used to template the synthesis of strained conjugated aromatics. In representative embodiments, the methodologies hereof may be extended to the synthesis of longer and more complex nanotube structures. As described further below, the compositions hereof may also be used, for example, in the formation of permanently porous liquids or PPLs (for example, for used in alkane/alkene gas separations), in forming container-shaped molecules for use in, for example, host-guest chemistry, in the formation of seeds for nanotubes, in the formation of nanoelectric devices such as supercapacitors and in other uses. The highly strained, aromatic architectures hereof, which have a tubular shape, are sometimes referred to herein as tubularenes as initial embodiments of such tubular structures were based on resorcin[n]arenes or upon calix[n]pyrrole-resorcinarenes.
As used herein “tubular” refers to an extending structure which is hollow or has an internal void. In a number of embodiments, the tubularenes hereof are conjugated atomically-precise cylindrical organic architectures that may, for example, be used as alternatives to CNTs or seeds for growing CNTs. In a number of embodiments, it is desirable that the tubular structures are as symmetrical as possible in cross-section over the axial length thereof. In a number of embodiments, the tubular structures are generally cylindrical.
In representative methods hereof, molecular precursors or end caps are first designed and synthesized, to obtain conjugated, atomically-precise cylindrical or tubular organic architectures or tubular[n]arenes. In that regard, the tubular structures hereof may be constructed through a bottom-up, Lego-like (or building-block) assembly of relatively small molecules or assemblies thereof of predetermined size, functionality and conformation which are used in the manner of building blocks. The predetermined size, functionality and conformation of the building blocks provides for controlled reactive, covalent assembly. In embodiments wherein conductive properties are of importance, the tubular[n]arene's electronic structure may be tailored by, for example 1) constructing them using a variety of electronically suitable building blocks (pre-synthesis), and 2) by post-synthetic covalent manipulations and/or metal coordination. In general, if electrical properties such as conductivity are important, it is desirable to maintain pi conjugation throughout the tubular wall of the tubular structure hereof (both axially and equatorially). The tubular[n]arene's electronic and ionic charge capacity properties may be readily characterized and their assembly into various devices may be readily explored.
Multi-wall CNTs have penetrated academic and commercial settings, where such CNTs find use in a wide range of applications such as solar cells, supercapacitors, coatings and films, batteries, composite materials, water filters, biosensors, among many more. All the latter examples use CNTs as polydisperse materials. Realizing strict control of size (diameter) and conductivity (chirality) promise to revolutionize the field of nanoelectronics. As described above, however, such control remains a significant challenge. Developing analogous wire-like compounds as described herein presents an attractive and potentially very rewarding avenue to explore.
Currently, there exists no analogues to carbon nanotubes. By developing synthetic approaches to conjugated nanotubes (either conducting and/or semiconducting) or molecular wires, compositions hereof may expand and improve the toolbox of electronic materials for nanodevices. The synthetic methods described herein are modular and tunable to hone the resulting nanotube for a particular application.
For example, CNT-based supercapacitors have been explored as high energy and power density devices. Such supercapacitors hold great promise in terms of durability. However, to realize them, CNTs have to be forest-grown in the electrode material. For best performance, such growth must occur as uniformly as possible. However, this growth remains a significant challenge in the construction of those devices. By introducing functionality into the nanotube, as possible in the tubularenes described herein, one may build uniform and controlled nanoforests with electroactive properties for supercapacitor applications.
Carbon allotropes such as graphene and CNTs have also had an important impact redefining new standards in materials properties. Alternative materials forming single layer 2D systems are currently under exploration to compete with graphene. Once again, however, no analogues exist for CNTs. Creating analogues of CNTs represents a large untapped potential for new materials discovery and/or development. For example, the methods hereof may be used in the synthesis of fluid, capsule-like molecules which may be used as separators of complex alkane/alkene mixtures. Such separations currently employ energy intensive cryogenic distillations.
Representative examples of tubular structures hereof with conductive properties are illustrated, for example, in
The formation of the tubular frameworks described herein is dependent on the end cap or macrocycle. In a number of embodiments hereof, the molecule forming the basis of the end cap should have two basic features: 1) it should be (semi)rigid and cyclic to translate its shape into a tubular or generally cylindrical geometry; and 2) it should contain free functional groups oriented into one (axial) direction to allow for preferential growth along this direction of the axis. In general, the end-cap or macrocycle should be sufficiently rigid so that, after accounting for its intrinsic degrees of freedom, it presents its functional groups oriented all in the same axial direction. Several macrocyclic compounds suitable for use herein are illustrated in
As described above, two representative, general families of compounds fulfill those requirement. The first general family of compounds is the resorcin[n]arene family of compounds as described above wherein macrocycles are built from condensation of resorcinol and an aldehyde. The second family of compound is the calix[n]pyrrole-resorcinarene family of compounds. Such families are highly modular since they allow the end group, R (as illustrated in
The terms “alkyl”, “aryl” or and other groups refer generally to both unsubstituted and substituted groups unless specified to the contrary. Unless otherwise specified, alkyl groups are hydrocarbon groups and are preferably C2 to C12 (that is, having 2 to 12 carbon atoms) alkyl groups, saturated and unsaturated (that is containing double bonds or not), and can be branched or unbranched, acyclic or cyclic. The above definition of an alkyl group and other definitions apply also when the group is a substituent on another group (for example, an alkyl group as a substituent of an alkylamino group or a dialkylamino group). The term “aryl” refers to phenyl or naphthyl, which may contain electron donating and withdrawing functional groups like carboxylic acid, esters, ethers, amines, where these functional groups may be substituted with alkyl groups as defined above. As used herein, the terms “halogen” or “halo” refer to fluoro, chloro, bromo and iodo. Heteroaryl/heteroarene groups may contain one or more heteroatoms such as N, O, S and P.
The term “amine” refers to the group —NRaRb, wherein Ra and Rb are for example, independently hydrogen, an acyl group, an alkyl group, and an aryl group. The term “alcohol” refers to the group —Rc, wherein Rc is, for example, an alkyl, aryl group, and a polyether which contains a free hydroxyl at the terminal or internal position of the overall fragment. The term “ether” refers to —RdORc wherein Rd and Re are, for example, independently alkyl and aryl as defined above.
Hydrophilic oligomers or hydrophilic polymers may, for example, be selected from the group consisting of hyaluronic acid, glucan, chitosan, a polyalkylene oxide, a polyvinylalcohol, a polyacrylic acid, a polyacrylamide, a polyoxazoline, a polysaccharide and a polypeptide. In a number of embodiments, the at least one hydrophilic polymer is a polyalkylene oxide. The polyalkylene oxide may, for example, be a polyethylene glycol. A polyethylene glycol or other hydrophilic polymer hereof may, for example, have a molecular weight in the range of 200 to 2000 Da in a number of embodiments.
The groups set forth above, can be substituted with a wide variety of substituents. For example, alkyl and other groups may be substituted with a group or groups including, but not limited to, a benzyl group, a phenyl group, a hydroxy group, an amino group (including, for example, free amino groups, alkylamino, dialkylamino groups and arylamino groups), and halo groups.
As used herein, the term “polymer” refers to a chemical compound that is made of a plurality of small molecules or monomers that are arranged in a repeating structure to form a larger molecule. Thus, a polymer is a compound having multiple repeat units (or monomer units) and includes the term “oligomer,” which is a polymer that has only a few repeat units. The term “copolymer” refers to a polymer including two or more dissimilar repeat units (including terpolymers—comprising three dissimilar repeat units—etc.). Polymers may occur naturally or be formed synthetically. The use of the term “polymer” encompasses homopolymers as well as copolymers. The term “copolymer” is used herein to include any polymer having two or more different monomers. Copolymers may, for example, include alternating copolymers, periodic copolymers, statistical copolymers, random copolymers, block copolymers, graft copolymers etc. Examples of polymers include, for example, polyalkylene oxides such as polyethylene glycol.
The number of aromatic units in the macrocycles or end caps hereof can be altered. For example, recent reports describe high-yielding syntheses for the 5- and 6-membered resorcin[n]arenes. Those compounds allow variability in the diameter of tubular structures hereof (see, for example,
The methodologies hereof, as, for example, illustrated schematically in
Representative compound 1a in
Representative extended or modified end caps formed with resorcin[4,5 and 6]arene 4a, 4b and 4c and calix[4]pyrrole 5 are illustrated in
An example of a general reaction sequence to obtain the tubular[n]arene 2a is illustrated in
As described above, the macrocyclic compounds, end caps or templates hereof are generally cylindrical and include arene groups in a number of embodiments. The macrocyclic compounds further include a plurality of functional groups oriented generally axially on one axial side of the macrocyclic compound. In a number of embodiments, the plurality of functional groups of the macrocycle is reacted with a first group or plurality of compounds or building blocks (for example, building blocks/compound groups 0, 1 and 2 of
In a number of embodiments, reactions with the halo groups include two general categories: (i) cross coupling reactions (see, for example,
The compounds of the first group of compounds further include one or more other functional groups which do not react with the plurality of functional groups of the macrocyclic compound under the first set of reaction conditions. After each of the first group of compounds is reacted with the macrocyclic compound, the one or more other functional groups may be oriented either to react with another group of compounds or building blocks hereof to extend the structure axially (as, for example, in compound 8 of building blocks/group 0 in the embodiment of
Once again referring to the embodiment of
In addition to illustrating representative building block compounds hereof,
Compound 8 of
The core or BB (see, the generalized formula of
In general, building blocks such as the representative building blocks of
Once again, in a number of embodiments hereof, programmed tubular growth may commence from resorcin[n]arene-based end cap such as compound 4a. The axial projection of the diamines predisposes the nanotube wall growth into one direction as, for example, illustrated in
Once again, the nanotube diameter is controlled by the end cap. Molecular models of compound 2a-c (4-membered (2a), 5-membered (2b), and 6-membered (2c) resorcin[n]arene derivatives) set forth diameters ranging from ˜13 to ˜19 Å, respectively (see
It is well-known that N-heteroacenes have a rich redox chemistry. By extension, tubular[n]arenes may display enhanced redox behavior since their walls may include multiple units of such heteroacenes conjugated. The charged states of such tubular structure may be determined by electrochemical methods as known in the art. These determinations, in turn, may be used to guide efforts of, for example, metal doping by performing stoichiometric chemical reductions. It is expected that the tubular[n]arene's conductivity properties will develop as the presence of itinerant or delocalized electrons is induced. Once may, for example, fine tune the end properties to form molecular wires.
Tubular[n]arenes or tubular structures hereof are a new family of organic compounds. As briefly described above, there are many potential applications for such compounds. As illustrated in
Another representative area of opportunity for compounds or tubular[n]arenes hereof is related to supercapacitors. Tubular[n]arene's redox activity, porous walls, and functional group terminus makes them good candidates in the construction of supercapacitors. As depicted in
In representative studies hereof, a series of tubular[n] arene precursors were designed and synthesized as illustrated by compounds 16a, 17a, and 18a of
Starting materials resorcin[4]arene 24 and 2,3-dichloro-5,8-dibromoquinoxaline 25 can, for example, be synthesized on a multigram scale. Reaction between 24 and 25 under basic conditions using triethylamine (TEA) in acetonitrile under reflux produces octabromo-derivative 23 in 57% yield. Under similar reactions conditions, Suzuki-Miyaura cross coupling of 23 with either 1,4-benzenediboronic or 1,4-naphthalenediboronic acid bis(pinacol) ester affords 21 and 22, respectively. The cross-coupling cyclization step provides rigidity and aromatic conjugation to 21 and 22, much like the walls of CNTs. In 21, this newly formed upper nanoring resembles [8]CPP as described in connection with
MALDI-TOF MS of tubularenes 21 and 22 display matching simulated values and isotopic distributions (
Asset forth above, the upper nanoring of 21 resembles [8]CPP, albeit with fewer degrees of freedom. The strain energy reported for [8]CPP is 72.2 kcal/mol, obtained by DFT at the B3LYP/6-31G(d) level of theory, considering a homodesmotic reaction. Following a similar approach at the same level of theory, we determined the strain energy of 21 to be 92.4 kcal/mol. DFT calculations at different levels of theory produced consistent values around 89±3 kcal/mol. The larger value for tubularene 21 relative to [8]CPP is expected, especially since 21 has only four out of eight phenyl rings that can freely rotate. In fact, free rotation is hampered at room temperature as observed in the vastly different chemical environments of a versus b protons at 6.8 and 8.7 ppm (
With respect to optoelectronic properties, species 21 and 22 display lowest energy absorption bands at λmax of 394 (ε=31380 L/mol·cm) and 402 (ε=12970 L/mol·cm) nm, respectively. These bands are red-shifted in comparison to the lowest energy transition of precursor 23 at λmax=338 (ε=42030 L/mol·cm) nm (
To gain further insight of the photophysical properties of compounds 21 and 22, we performed time-dependent (TD) DFT calculations at various levels of theory. For both tubularenes, we found that the HOMO-to-LUMO transition is forbidden, as in [n]CPPs. A structure-function relationship has previously been between octamethoxy-[8]CPP (λem=458 nm) and [8]CPP (?em=535 nm) indicating that a bathochromic shift in emission corresponds to increased radial π-conjugation. Extrapolating this correlation to the emissive properties of 21 and 2 supports the conclusion that the tubularene's rigidity assists in maintaining a large n-conjugated surface, although not as much as [8]CN (λem=570 nm).
Electrochemically, tubularenes 21 and 22 display a rich series of reductive events in ortho-dichlorobenzene. Cyclic voltammograms (CVs) exhibit onset of reduction at around −1.95 and −2.05 V vs Fc/Fc+ for 21 and 22 (
The CV of tubularene 21 displays four reduction events on the cathodic scan, but since these are clustered together, it is not possible to extract the half-wave potentials (E½) from the CV alone. Fortunately, by differential pulse voltammetry (DPV trace in
The electrochemical LUMO levels (ELUMO) were calculated for 21 and 22 by employing E½ of the first reduction event according to ELUMO=−[E½+4.80] eV. Additionally, the HOMO energy level was obtained by subtracting Egap from ELUMO. HOMO and LUMO levels for 21 and 22 are plotted in
Last, to gain further insight into the rigidity effect of tubularene 21 into electron delocalization across the aromatic framework, DFT calculations were performed on the radicals formed in 21 after removing an electron from the HOMO (1+•) and adding an electron to the LUMO (1−•). Results show the spin density of the radical completely delocalized across the conjugated backbone of 21, in stark contrast to [8]CPP and other similar contorted aromatics, where the radical is mostly localized into a portion of the molecule.
Synthesis and characterization of further tubularenes is illustrated in
In effecting selective separations such as separation of fullerenes, the tubular structures/compounds hereof may, for example, be reacted with substrate or structure (for example, a porous or permeable membrane) via functional R groups on the tubular structures/compound with reactive functional groups of the substrate or structure to form a separation article or structure (for example, a membrane, a surface, etc.). Alternatively, the R groups of the tubular structures/compounds hereof may be polymerizable as described above to from such a separation article or structure.
Synthesis of the Compound of
A Pyrex Schlenk flask was loaded with 0.3 g of Octa-Br template (0.16 mmol), 0.3 g of 1,4-benzenediboronic acid bis(pinacol) ester, and 1.2 g of K2CO3 in 250 mL of toluene, 25 mL of water and 25 mL of EtOH. The reaction mixture was degassed for 30 min while stirring vigorously at room temperature. To this mixture, 0.18 g of Pd(PPh3)4 (0.16 mmol, 1 eq) was added. The solution was degassed again for an additional 15 min while gradually increasing the temperature to 70° C. This reaction was repeated three times. The solvent was removed under vacuum and the resulting solid passed through a flash column using pure DCM in hexanes. The final product was purified using 70% DCM in hexanes by preparatory TLC.
Synthesis of the Compound of
A Pyrex Schlenk flask was loaded with 0.3 g of Octa-Br template2 (0.16 mmol), 0.3 g of 1,4-benzenediboronic acid bis(pinacol) ester (or Octa-Br template3 and Thieno[3,2-b]thiophene, 2,5-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl) and 1.2 g of K2CO3 in 250 mL of toluene, 25 mL of water and 25 mL of EtOH. The reaction mixture was degassed for 30 min while stirring vigorously at room temperature. To this mixture, 0.18 g of Pd(PPh3)4 (0.16 mmol, I eq) was added. The solution was degassed again for an additional 15 min while gradually increasing the temperature to 70° C. This reaction was repeated three times. The solvent was removed under vacuum and the resulting solid passed through a flash column using 50% EtAc in hexanes. The final product was purified using 25% EtAc in hexanes by preparatory TLC.
Synthesis of the Compounds of
A Pyrex Schlenk flask was loaded with 0.3 g of Octa-Br template4 (0.16 mmol), 0.15 g of 1,4-benzenediboronic acid bis(pinacol) ester and 0.15 g of 1,3-toluenediboronic acid bis(pinacol)ester, and 1.2 g of K2CO3 in 250 mL of toluene, 25 mL of water and 25 mL of EtOH. The reaction mixture was degassed for 30 min while stirring vigorously at room temperature. To this mixture, 0.18 g of Pd(PPh3)4 (0.16 mmol, 1 eq) was added. The solution was degassed again for an additional 15 min while gradually increasing the temperature to 70° C. This reaction was repeated three times. The solvent was removed under vacuum and the resulting solid passed through a flash column using 70% DCM in hexanes. The final products (m4, m3p1, m2p2 and m1p3) were purified using 50% DCM in hexanes by preparatory TLC.
Synthesis of the Compounds of
A mixture of 2,2′-bipyridine (21 eq), 1,5-cyclooctadiene (21 eq), and bis(1,5-cyclooctadiene)nickel(0) (21 eq) in a mixture of degassed toluene (40 mL) and DMF (40 mL) was stirred at 80° C. for 20 min. To the mixture at 80° C. was added a solution of octa-chloro compound 1 or 2 (200 mg) in toluene (20 ml) dropwise over 1 h, and the mixture was stirred at 80° C. over the night. After the reaction mixture was cooled down to ambient temperature, the solvents were dried using rotavapor and black solid passed though the flash column with pure DCM. The product has been purified using column chromatography using 50% DCM in hexanes. These reactions have been carried out with derivatives containing two different alkyl tails R═C5H11 or C11H23.
The foregoing description and accompanying drawings set forth a number of representative embodiments at the present time. Various modifications, additions and alternative designs will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the scope hereof, which is indicated by the following claims rather than by the foregoing description. All changes and variations that fall within the meaning and range of equivalency of the claims are to be embraced within their scope.
This application claims benefit of U.S. Provisional Patent Application Ser. No. 63/057,506, filed Jul. 28, 2020, the disclosure of which is incorporated herein by reference.
Number | Date | Country | |
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63057506 | Jul 2020 | US |