Porphene, a heterocyclic analog of graphene, methods of making and using the same

Abstract

Methods of forming a porphene polymeric material are provided. The resulting material can be a porphene or a metalloporphene polymeric material. The structure of the polymer can be selected based on a material provided in the monomer material. Methods of using the polymeric material are also provided.

Claims

1. A porphene polymer, comprising: polymerized monomers of porphyrin, wherein the porphyrin is a macrocyclic molecule comprising four nitrogen atoms, wherein a structure of the porphene polymer is a single layer, a double layer, or a multilayer, wherein a thickness of the single layer, double layer, or multilayer is no more than about 5 nm, wherein the monomers of porphyrin are directly fused to each other, and wherein the single layer, double layer, or multilayer is at least three monomers of porphyrin in length and at least three monomers of porphyrin in width.

2. The polymer of claim 1, wherein the porphene polymer further comprises a dication.

3. The polymer of claim 2, wherein the dication is zinc, platinum, iron, nickel, or two hydrogen atoms, and combinations thereof.

4. The porphene polymer of claim 1, wherein a charge of the porphene polymer is neutral.

5. The porphene polymer of claim 1, wherein the polymer comprises meso-meso and meso-beta bonds.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

(2) FIG. 1A illustrates a first tautomer of a free-base porphene wherein the bonds with hydrogen are diagonally disposed in the different directions;

(3) FIG. 1B illustrates a second tautomer of a free-base porphene wherein the bonds with hydrogen diagonally disposed in the same direction;

(4) FIG. 2 illustrates structures of metalloid porphene where M represents a metal dication;

(5) FIG. 3A illustrates a zinc porphene polymer, wherein the calculated relative energy is about 0.85 kcal/mol per macrocyclic unit, relative to the most stable isomer;

(6) FIG. 3B illustrates a zinc isoporphene polymer, wherein the calculated relative energy is 0 kcal/mol per macrocyclic unit, this is the most stable isomer;

(7) FIG. 3C illustrates a zinc neoporphene polymer, wherein the calculated relative energy is about 201.32 kcal/mol per macrocyclic unit, relative to the most stable isomer;

(8) FIG. 4A illustrates a mechanism showing monomer coupling mechanism to form a dimer;

(9) FIG. 4B the dimer further growth mechanism shows the formation of a trimer;

(10) FIG. 4C illustrates the macrocycle fusion mechanism in the dimer;

(11) FIG. 5 illustrates a time series of UV-vis spectra showing the transformation of zinc porphyrin (ZnP) to porphene by oxidative polymerization;

(12) FIG. 6 illustrates the grazing incidence X-ray diffraction (GIXD) of bilayer porphene prepared from Zn-porphyrin and monolayer porphene prepared from Pt-porphyrin by oxidative polymerization at the air/water interface;

(13) FIG. 7A illustrates a X-ray reflectivity of a layer of monomeric zinc porphyrin at the air/water interface;

(14) FIG. 7B illustrates the fitted electron density of a layer of monomeric zinc porphyrin;

(15) FIG. 8A illustrate a X-ray reflectivity of a porphene film synthesized from zinc porphyrin at the air/water interface;

(16) FIG. 8B illustrates the fitted electron density of zinc porphene showing the contribution of the anions just below the water surface;

(17) FIG. 9 illustrates unit cell for a double layer of porphene produced by oxidative polymerization of Zn-porphyrin at the air/water interface (uncoupled before polymerization and coupled after polymerization);

(18) FIG. 10 illustrates a X-ray photoelectron spectrum (XPS) of porphene produced by oxidative polymerization of Zn-porphyrin prior to transfer to a substrate;

(19) FIG. 11 illustrates an atomic force microscopy (AFM) image of a double sheet of porphene after transfer to a HOPG substrate, tens of microns in size, synthesized from zinc porphyrin;

(20) FIG. 12 illustrates an AFM image of a double sheet of porphene after transfer to a Ge substrate, tens of microns in size, synthesized from zinc porphyrin;

(21) FIG. 13 illustrates an AFM image of porphene sheets synthesized from Pt-porphyrin, conforming to HOPG step edges;

(22) FIG. 14: Ambient Scanning Tunneling Microscopy (STM) image of porphene sheet synthesized from Pt-porphyrin, after transfer to a HOPG substrate;

(23) FIG. 15 illustrates a Transmission Electron Microscopy (TEM) image of porphene monolayer synthesized from Pt-porphyrin and suspended over a hole in lacey carbon.

(24) Magnification: 490 000×, beam energy: 200 keV;

(25) FIG. 16A illustrate an AFM image of Ni-porphene on a HOPG substrate;

(26) FIG. 16B illustrate an AFM image of Ni-porphene on a HOPG substrate;

(27) FIG. 16C illustrates the cross section analysis of the tube heights;

(28) FIG. 17A illustrates an AFM image of porphene single layer sheets on a HOPG substrate;

(29) FIG. 17B illustrates an AFM image of porphene single layer sheets on a HOPG substrate; and

(30) FIG. 18 illustrates the TEM image of Fe-porphene on lacey carbon obtained at a beam energy of 200 keV and 1,460,000× magnification.

DETAILED DESCRIPTION

(31) An aspect of the invention is a porphene polymer. The monomer, porphyrin, contains several rings, including a macrocycle with 16 atoms, of which four are nitrogens and 12 are carbons. The macrocycle can contain either two protons (“free-base porphyrin”) or a 2+ charged cation in the center of its ring (“metalloporphyrin”). When the protons are present, they are attached to two of the nitrogen atoms, diagonally disposed. When a double cation is present, it is attached to all four nitrogen atoms. In the porphene polymer, the monomer repeats in two dimensions. The structure of the monomer unit has been known, but the polymerization of the monomer as well as the resulting polymer are novel.

(32) The synthetic method involves providing an aqueous fluid with an exposed surface area. A monomer of porphyrin or metalloporphyrin is provided to the exposed surface area. An oxidant is provided on either side of the surface to induce the coupling of the monomer to produce the polymer. Oxidant concentrations can be between about 0.01 mM and 10 mM.

(33) In some embodiments, the porphyrin monomer can contain two protons in every macrocycle and in others it contains a doubly positive 2+ ion such as zinc, platinum, or nickel instead. In some embodiments, any transition or main-group metal dication or combination of transition or main-group metal dications that have been inserted into a monomeric porphyrin could be used with the polymeric porphene. Suitable metals include zinc, platinum, nickel, but there are other suitable double cation materials. By way of example the type of metal used in the starting monomer can alter the structure of the end polymer. When zinc is used, the structure of the resulting porphene polymer material is a double layer. When platinum is used, the structure of the porphene polymer material is a monolayer. When nickel is used, the structure of the porphene polymer material is a tube or coil. It is likely that preorganization of the monomeric metalloporphyrin on the surface of the aqueous subphase is different in each case as a result of the different number of ligands favored by different metals and of the non-planarity of certain metalloporphyrins.

(34) The metal dication does not remain in the polymer and is leached into the aqueous subphase. Since the oxidant must be strong enough to perform a one-electron oxidation of the monomer, it is therefore also strong enough to oxidize the much more extensively conjugated polymer, injecting positive electron “holes” into it and charging it strongly positively. In some embodiments, the oxidant potential of the oxidant can be about 0.65 V against Ag/AgCl. X-ray reflectivity measurement illustrates the density of electrons projected into the normal to the surface and illustrates that the surface section of the aqueous sublayer contains an excess of anions and is thus negatively charged to compensate for the positive charges in the polymer. When transferred onto a substrate, electrons can move between the substrate and the polymer and the net positive charge of the porphene layer or layers can change. The actual charge on the polymer at final equilibrium will be a function of the nature of the substrate material. If the substrate is conducting, such as highly oriented pyrolytic graphite (HOPG) or indium tin oxide (ITO), and its electrical potential is well defined, it will dictate the position of the Fermi level and the degree of charging of the polymer. If it is insulating, the positive charge remaining on the polymer can be controlled by the selection of the substrate material. If the substrate is an insulating material, then it is more difficult to control the charge on the polymer. However, it is possible to remove all the positive charges by adding a reductant such as the iodide anion into the subphase before the transfer. Once the positive charges are removed, it is easy to insert metal dications into the macrocycles in the polymer by adding their salt into the subphase.

(35) The porphene sheets can be synthesized as a single or a double layers by a suitable choice of metal in the starting metalloporphyrin. Sheets can also be folded or superimposed to form multilayers. These layers can be stacked, for example in a perfectly eclipsed manner (such that like atoms exactly above each other), or slipped with respect to each other in various directions, or even twisted about the surface normal by 0 to 45 degrees.

(36) In some embodiments, about 1.5×10.sup.14 monomers can be used to produce a 1 cm.sup.2 of polymer. In some embodiments, the surface density of the polymer can be about 0.68 ng/cm.sup.2. If the polymer is distributed in 1 cm.sup.2 sheets, the effective molecular weight can be about 4.2×10.sup.16 g/mole. When the material is a metalloporphene, the molecular weight or surface density of the free base porphene given above is scaled by the molecular weight of the metalloporphyrin monomer—12.1 g/mole)/(molecular weight of free base porphyrin—12.1 g/mole). One skilled in the art can calculate or determine the molecular weight when the surface density of the polymer is known.

(37) Intimate contact places neighboring porphene sheets, depending on their degree of interlayer hydration, which, in turn, depends on the metal center, between about 0.3 nm and about 0.8 nm apart and their total number then dictates the thickness of the total polymer stack. The thickness of a single layer can be between about 0.3 nm and about 0.4 nm. Depending on the exact conditions of the synthesis, the observed lateral dimension of the sheets has been as small as 2 nm and as large as 10 mm across, and could possibly be even larger than 1 cm.sup.2, in some embodiments up to 1 min length, width or both.

(38) A Langmuir-Blodgett (LB) layer is prepared on an aqueous subphase. This method is described with relation to a LB trough, but one skilled in the art would understand other suitable systems to provide a layer on a subphase without deviating from the invention. Other suitable methods can also be used. The amount starting material to form LB layer will depend on the size of the LB trough and is chosen to maintain a desired mean molecular area between about 0.4 nm.sup.2 and about 1.5 nm.sup.2. The thickness of the LB layer can be between about 0.1 nm and about 5 nm. The aqueous subphase can be water (18 MOhm, deionized, distilled, tap or combinations thereof and devoid of all organic contaminants), or a salt solution. The amount of the aqueous subphase can be between a small drop to liters in volume and will again generally be dependent on the size of the LB trough. The concentration of the oxidant can be between about 0.01 mM and about 10 mM, in some embodiments about 10.sup.−5 M. The oxidant can be K.sub.2IrCl.sub.6, Ce(NO.sub.3).sub.6.sup.2−, ClO.sub.2, ClO.sub.3.sup.−, Ru(bipy).sub.n.sup.3+, Os(bipy).sub.n.sup.3+, or Ru(CN).sub.6.sup.3−. The amount of the unsubstituted porphyrin added to the system can be between about 1 ng and about 1 mg and again depend on the size of the trough. The ratio of the unsubstituted porphyrin to the oxidant/aqueous subphase can be between about 1:1 and about 1:10. The temperature after the oxidant is added to the aqueous subphase can be between about 0° C. and about 100° C., in some embodiments between about 22° C. and about 30° C. The course of oxidative polymerization can be monitored on the surface of the LB trough using suitable methods including isotherm determination, UV-vis absorption, grazing incident diffraction (GIXD), X-ray reflectivity (XR) or combinations thereof until the polymer is formed on at least 10% of the surface area of the LB layer.

(39) A pressure can be applied to the monomers during the formation of the polymer. By way of example, when a LB trough is used the surface pressure change relative to a clean subphase surface can be less than about 1 nM/m. In some embodiments, the temperature during the polymerization process can be between about 20° C. and about 40° C., in some embodiments about 25° C. The reaction can take place in ambient light. The reaction can also take place in saturated humidity, which can be provided by using a cover (e.g. a dust cover) on the system. In some embodiments, about 24 hours can be needed to result in the maximum degree of polymerization.

(40) Notably, the resulting polymer is a free base. The metal (e.g. zinc, platinum or nickel) present in the monomer will be leached out into the aqueous subphase. Though not wanting to be bound by theory, it is believed that the oxidizing agent selected is strong enough to oxidize the monomer to its radical cation to initiate its polymerization. The much more highly conjugated polymer is easier to oxidize to a polyradical polycation and in its oxidized positively charged state expels the metal cation into the subphase. The concentration of the metal remaining in the polymer porphyrin is less than about 1%, in some embodiments.

(41) A reducing agent, such as an iodide, sulfite, thiosulphate, and the like can be added to the subphase mixture at a concentration of between about 0.001M and about 0.1M. The reducing agent reduces/destroys the oxidizing agent. The reducing agent also reduces the polymer present on the surface to an electroneutral state. In some embodiments, a desired cation can be added to the subphase mixture. The desired cation can be Zn.sup.2+, Fe.sup.2+, FeCl.sup.2+, or other divalent cations, and combinations thereof. The cation can be added to the subphase mixture by adding its salt to a concentration of about 0.01 M to about 0.1 M. The cation of the subphase mixture can insert itself into the porphene that is present on the LB layer. The cation can be present in between a small fraction and about 1000:1 of the porphene depending on the desired final fraction or rate of insertion.

(42) The polymer can be transferred from the aqueous subphase surface to a substrate using standard LB techniques. Suitable substrates include a solid substrate, a metal grid or lacey carbon substrate. The material of the substrate can be a metal, such as stainless steel, an aluminum alloy, gold, and oxide, such as indium tin oxide; a polymer, such as PMMA; glass; other materials, such as a germanium or silicon substrate, terraces of HOPG or combinations thereof. The transfer to the substrate can occur after a set period of time or at intervals during the polymerization process. In some embodiments, the surface of the substrate can be pretreated by washing the surface successively with tetrahydrofuran (THF), spectroscopic grade chloroform, spectroscopic grade benzene and spectroscopic grade isopropanol with air drying between each step. In some embodiments, substrates can be treated in Nano-strip® for about 10 mins. followed by the solvent treatment. Following the transfer to the substrate, the cation (when present) remains in the porphene. Further, the porphene can cover between about 1% and about 100% of the surface area of the substrate. In some embodiments, the strength of the porphene to the substrate can be quite high and comparable to paint or other well-known coatings.

(43) The transferred polymer can form ultrathin (between about 0.3 nm and about 50 nm, in some embodiments about 1 nm) flakes. The width/length of the flakes can be between 10 nm and about 10 mm, in at least one dimension.

(44) In some embodiments, ligands, for example water, can be present in the polymer. Removing the ligands can reduce the interlayer spacing by an amount that is dependent on the size and type of ligand removed. To remove water ligands, a porphene sample transferred to a substrate by LB techniques is heated under a controlled atmosphere (N.sub.2, Ar or clean air) at about 130° C. for 1 hour.

(45) An aspect of the invention is a method of using the porphene material. There are many potential uses: as separation membranes, for example a membrane that would permit the passage of small cations (H+, Li+, etc.) to be more facile than that of larger cations, as constituents of metalorganic materials (MOFs), as sensors, catalytic and electrocatalytic materials, as components in nanoelectronics, as heterojunction materials, as memory or qubit elements, as means of positioning metal atoms or metal clusters on a surface in regular square arrays, etc.

EXAMPLES

Example 1: Formation of Bilayer Porphene from Zinc Porphyrin

(46) Porphene was produced from the oxidative coupling of zinc porphyrin monomers at the air water interface of a Langmuir-Blodgett (LB) trough. Zinc porphyrin was either synthesized (method described in the Porphyrin Handbook, previously incorporated by reference) or commercially obtained and spread from a benzene solution onto the aqueous subphase using standard Langmuir-Blodgett techniques to obtain a mean molecular area (mmA) of 125 Å.sup.2. In this concentration range the monomers lie flat on the surface of the liquid subphase. An oxidant, 10.sup.−5 M K.sub.2IrCl.sub.6, was added to the aqueous subphase to induce oxidative polymerization of the monomers on the surface. The reaction progress was monitored in situ over the course of several hours using UV-vis absorption. UV-vis spectra of the surface of the aqueous phase were collected as a function of time in the compartment of a Cary 2000 double-beam spectrometer. FIG. 5 illustrates the difference between UV-vis spectra collected at various time intervals (t=x) and the spectrum collected at t=0 prior to the addition of the oxidant. As the polymerization reaction proceeds there is a gradual loss of the Soret band (at about 375 nm) which is attributed to the loss of zinc porphyrin monomer and there is an increase in broad unstructured peaks at longer wavelengths (>450 nm) that are associated with the meso-meso and the beta-beta coupling of monomers to form the polymer. Subtracted is the spectrum of the uncoupled ZnP at t=0.

(47) GIXD and X-ray Reflectivity data were collected using the synchrotron using the ChemMat/CARS facility at the APS synchrotron at Argonne National Laboratory. The upper part of FIG. 6 illustrates the GIXD spectrum of the zinc porphyrin monomers and of porphene at approximately 6 hrs. following initiation of the reaction. Zn-porphene is a bilayer, and Pt-porphene is a monolayer.

(48) FIGS. 7A and 8A illustrate X-ray reflectivity measurements, while FIGS. 7B and 8B illustrate the density of electrons projected normal to the surface for the zinc porphyrin and porphene, respectively. The data show that the resulting polymer has a bilayer structure with two planar sheets positioned parallel to one another. The polymer is in its free-base form indicating that the zinc that is present in the monomer, and in the polymer following its initial formation, is leached out from the polymer into the subphase. The loss of zinc from the polymer is attributed to the net positive charge on the polymer due to injection of holes into the polymer by the oxidant. Notably, the density of electrons projected normal to the surface of the subphase, determined from X-ray reflectivity data, shows a surface section of the aqueous sublayer that contains an excess of anions to compensate for the positive charges in the polymer (see FIG. 8B).

(49) The GIXD and X-ray reflectivity data were used to derive the dimensions of the unit cells and the bilayer structures of the assemblies before oxidative coupling and after coupling. These results are provided in FIG. 9 (uncoupled on the left and coupled on the right). Before the oxidative coupling, the side of the four Zn square is 11.2 Å long and the two layers are shifted diagonally by −¼ of the unit cell, such that the Zn atoms of one layer are located approximately above a pyrrole ring of the other. The area of the unit cell is 62.7 Å.sup.2 and the bilayer thickness is 7.1 Å.

(50) In the oxidatively polymerized coupled structure, the zinc previously present has now been leached from the structure such that the polymer is in the free-base form. In this case, the distance between centers of the nitrogen quadrangle is 8.9 Å, the two layers are shifted diagonally by ½ of the unit cell such that center of the nitrogen quad of one layer is located above an 8-membered ring of the other layer. Other properties are listed in Table 1.

(51) TABLE-US-00001 TABLE 1 Uncoupled Coupled Angle (degrees) 66.1 (α) 53.0 (β) Length (Å) 11.2 8.9 Width(Å) 11.2 8.4 Angled height (Å) 6.9 6.7 Height (Å) 5.7 5.7 Thickness from reflectivity (Å) 7.1 32 Single crystalline domain length (nm) >80 >80 Mean molecular area (Å.sup.2) 62.7 Å.sup.2 cf. 62 36.4 Å.sup.2 cf. 30-40 Å.sup.2 from LB Å.sup.2 from LB isotherm isotherm

(52) Notably, the X-ray reflectivity data provides a bilayer thickness of 32 Å, however, this number contains an unknown contribution from the layer of IrCl.sub.6.sup.2− counterions expected to accompany the positively charged polymer.

(53) The bilayer porphene sheets were transferred onto a substrate for further analysis. The transferred polymer forms ultrathin (˜1 nm) flakes up to several mm across. When transferred onto a substrate, electrons can move between the substrate and the polymer and the net positive charge of the porphene layer or layers can change. The actual charge on the polymer at final equilibrium will be a function of the nature of the substrate material. If the substrate is conducting (e.g., such as in highly oriented pyrolytic graphite (HOPG) or indium tin oxide (ITO)) and its electrical potential is well defined, it will dictate the position of the Fermi level and the degree of charging of the polymer. If the substrate is insulating, the positive charge remaining on the polymer can be controlled by the selection of the substrate material. However, all positive charges can also be removed from the polymer before the transfer by treatment with a reductant, such as the iodide or bisulfite anion (see example 5).

(54) Porphene sheets were transferred onto Si, ITO or HOPG substrates and were analyzed using X-ray photoelectron spectroscopy (XPS, KRATOS). FIG. 10 illustrates a X-ray photoelectron spectrum (XPS) of porphene produced by oxidative polymerization of Zn-porphyrin prior to transfer to a substrate. The data illustrated in FIG. 10 confirm that the polymer is in the free-base form and that essentially all of the zinc has been leached from the polymer. The spectrum shows intense C.sub.1s and O.sub.1s peaks and weaker N.sub.1s peak. The O.sub.1s peak indicated that polymer is hydrated.

(55) FIGS. 11 and 12 illustrate atomic force microscopy (AFM) images of the bilayer porphene sheets after transfer to HOPG and germanium substrates, respectively. These images show the durability of the polymer film. The first image shows terraces of HOPG draped by a sheet of porphene. The second image shows micron sized islands of porphene. However, also apparent are tears in the sheet due to the transfer of the film to the substrate.

Example 2: Formation of Porphene Sheets from Platinum Porphyrin

(56) Porphene was produced from the oxidative coupling of platinum porphyrin monomers at the air water interface of a LB trough using a method similar to that described in Example 1. Platinum porphyrin was synthesized from commercially obtained porphine (free-base porhyrin) and spread on to the aqueous subphase from a benzene solution using Langmuir-Blodgett techniques to obtain a mean molecular area (mmA) of 125 Å.sup.2. The aqueous subphase was adjusted to about 10.sup.−4 M K.sub.2IrCl.sub.6 to induce oxidative polymerization of the monomers on the surface. Polymerization was complete after 6-8 hours.

(57) The reaction progress was monitored using GIXD. The lower part of FIG. 6 shows the GIXD of the Pt-porphyrin monomer and porphene polymerization. The Pt-monomer forms a buckled monomer layer on the aqueous surface and has a Pt-Pt distance of 8.7 Å and a mean molecular area of 80 Å.sup.2 at 10 nM/M. The resulting porphene polymer is in the free-base form and is a flat single sheet with a center-to-center (i.e., measured from the center of one monomer to the center of a neighboring monomer) distance of 8.4 Å and a mean molecular area of 70 Å.sup.2 at 2.5 nm/m.

(58) The porphene sheets were transferred onto a substrate for further analysis. FIG. 13 shows an AFM image of porphene on a HOPG substrate. The image shows micrometer-sized flakes or islands of the porphene that conform to step edges on the surface. FIG. 14 shows ambient Scanning Tunneling Microscopy (STM) image of porphene sheet synthesized from Pt-porphyrin, after transfer to a HOPG substrate. FIG. 15 illustrates a Transmission Electron Microscopy (TEM) image of porphene monolayer synthesized from Pt-porphyrin and suspended over a hole in lacey carbon. Magnification: 490 000×, beam energy: 200 keV. The image shows flakes of porphene that are approximately hundreds of nanometer in diameter. Magnification of the image shows the organization of the monomer layer.

Example 3: Formation of Porphene Tubes from Nickel Porphyrin

(59) Porphene was produced from the oxidative coupling of nickel porphyrin monomers at the air water interface of a LB trough using a method similar to that described in Example 1. Nickel porphyrin was synthesized from commercially obtained porphine (free-base porphyrin) and spread on to the aqueous subphase from a benzene solution using standard Langmuir-Blodgett techniques to obtain a mean molecular area (mmA) of 125 Å.sup.2. The aqueous subphase was adjusted to about 10.sup.−4 M K.sub.2IrCl.sub.6 of the aqueous subphase to induce oxidative polymerization of the monomers on the surface. Polymerization was complete after 6-8 hours.

(60) Following polymerization, porphene was transferred onto a substrate for further analysis. FIGS. 16A and 16B illustrate an AFM image of Ni-porphene on a HOPG substrate. The formation of porphene from nickel porphyrin results in a porphene nanotubes that range in height from 20 to 80 Å. FIG. 16C illustrates the cross section analysis of the tube heights.

Example 4: Formation of Bilayer Porphene from Free-Base Porphyrin

(61) Porphene was produced from the oxidative coupling of the free-base porphyrin monomers at the air water interface of a Langmuir-Blodgett (LB) trough using a method similar to that described in Example 1. Porphine (free-base porphyrin) was obtained commercially and spread on to the aqueous subphase from a benzene solution using Langmuir-Blodgett techniques to obtain a mean molecular area (mmA) of 125 Å.sup.2. The aqueous subphase was adjusted to about 10.sup.−4 M K.sub.2IrCl.sub.6 to induce oxidative polymerization of the monomers on the surface. Polymerization was complete after 6-8 hours.

(62) Following polymerization, porphene was transferred onto a substrate for further analysis. FIG. 17A and FIG. 17B illustrates an AFM image of porphene on a HOPG substrate. FIG. 17B illustrates a more cohesive layer compared to the porphene illustrated in FIG. 17A.

Example 5: Formation of Zn-Porphene Sheet

(63) Porphene was produced from the oxidative coupling of zinc porphyrin monomers at the air water interface of a LB trough using a method similar to that described in Example 1 except that following polymerization, a reducing agent (1 mMoles of NaI) was added to the aqueous subphase (250 mL) to destroy the oxidizing agent and reduce the polymer to an electroneutral state. Zn.sup.2+ cations were then re-introduced into the porphene bilayer. ZnCl.sub.2 (1.3 mMoles) was added to the aqueous subphase (250 mL) to form Zn-porphene bilayer sheets after the reduction was completed. The full formation of the Zn-porphene sheet requires 24 hours. The transformation to Zn-porphene is verified by IR spectroscopy.

Example 6: Formation of Fe-Porphene Sheets

(64) Fe-porphene was synthesized from free base porphyrin to form porphene and Fe was subsequently introduced into the polymer. Fe-porphene was transferred onto a lacey carbon substrate. FIG. 18 shows the TEM image obtained at a beam energy of 200 keV and 1,460,000× magnification. The image shows the ordered structure of the monomer layers.

(65) Ranges have been discussed and used within the forgoing description. One skilled in the art would understand that any sub-range within the stated range would be suitable, as would any number within the broad range, without deviating from the invention.

(66) The foregoing description of the present invention, related to a porphene polymer and methods of making the same, has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and the skill or knowledge of the relevant art, are within the scope of the present invention. The embodiment described hereinabove is further intended to explain the best mode known for practicing the invention and to enable others skilled in the art to utilize the invention in such, or other, embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.