@article{schmidt_jiao_bocian_lindsey_2008, title={A Bipodal-Tethered Porphyrin for Attachment to Silicon Surfaces in Studies of Molecular Information Storage}, volume={8}, ISSN={["1533-4899"]}, DOI={10.1166/jnn.2008.IC85}, abstractNote={An approach for molecular information storage entails use of redox-active molecules attached to an electroactive surface. Understanding the structural features that give rise to robust molecular monolayers with high charge density is an essential objective. Toward this goal, a zinc-porphyrin
 bearing an all-carbon bipodal tether, 5-(1,6-heptadien-4-yl)-15-phenyl-10,20-di-p-tolylporphinatozinc(II), has been synthesized by the reaction of a dipyrromethane and a dipyrromethane-1,9-dicarbinol. The porphyrin was attached to Si(100) via a high temperature procedure. The resulting
 molecular monolayers exhibited surface coverages, adsorption geometries, electron-transfer rates, and stabilities under repeated electrochemical cycling that are similar to those obtained with monopodal carbon tethers. The observation that the bipodal anchor does not provide enhanced stability
 is surprising given that attachment is achieved via two versus one covalent linkage.}, number={9}, journal={JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY}, author={Schmidt, Izabela and Jiao, Jieying and Bocian, David F. and Lindsey, Jonathan S.}, year={2008}, month={Sep}, pages={4813–4817} }
 @article{jiao_schmidt_taniguchi_lindsey_bocian_2008, title={Comparison of Electron-Transfer Rates for Metal- versus Ring-Centered Redox Processes of Porphyrins in Monolayers on Au(111)}, volume={24}, ISSN={["0743-7463"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-55549087896&partnerID=MN8TOARS}, DOI={10.1021/la8019843}, abstractNote={The standard electron-transfer rate constants ( k ( 0 )) are measured for redox processes of Fe versus Zn porphyrins in monolayers on Au(111); the former undergoes a metal-centered redox process (conversion between Fe (III) and Fe (II) oxidation states) whereas the latter undergoes a ring-centered redox process (conversion between the neutral porphyrin and the pi-cation radical). Each porphyrin contains three meso-mesityl groups and a benzyl thiol for surface attachment. Under identical solvent (propylene carbonate)/electrolyte (1.0 M Bu 4NCl) conditions, the Zn (II) center has a coordinated Cl (-) ion when the porphyrin is in either the neutral or oxidized state. In the case of the Fe porphyrin, two species are observed a low-potential form ( E l (0) approximately -0.6 V) wherein the metal center has a coordinated Cl (-) ion when it is in either the Fe (II) or Fe (III) state and a high-potential form ( E h (0) approximately +0.2 V) wherein the metal center undergoes ligand exchange upon conversion from the Fe (III) to Fe (II) states. The k ( 0 ) values observed for all of the porphyrins depend on surface concentration, with higher concentrations resulting in slower rates, consistent with previous studies on porphyrin monolayers. The k ( 0 ) values for the ring-centered redox process (Zn chelate) are 10-40 times larger than those for the metal-centered process (Fe chelate); the k ( 0 ) values for the two forms of the Fe porphyrin differ by a factor of 2-4 (depending on surface concentration), the Cl (-) exchanging form generally exhibiting a faster rate. The faster rates for the ring- versus metal-centered redox process are attributed to the participating molecular orbitals and their proximity to the surface (given that the porphyrins are relatively upright on the surface): a pi molecular orbital that has significant electron density at the meso-carbon atoms (one of which is the site of attachment of the linker to the surface anchoring thiol) versus a d-orbital that is relatively well localized on the metal center.}, number={20}, journal={LANGMUIR}, publisher={American Chemical Society (ACS)}, author={Jiao, Jieying and Schmidt, Izabela and Taniguchi, Masahiko and Lindsey, Jonathan S. and Bocian, David F.}, year={2008}, month={Oct}, pages={12047–12053} }
 @article{anariba_tiznado_diers_schmidt_muresan_lindsey_zaera_bocian_2008, title={Comprehensive characterization of hybrid junctions comprised of a porphyrin monolayer sandwiched between a coinage metal overlayer and a Si(100) substrate}, volume={112}, ISSN={["1932-7447"]}, DOI={10.1021/jp802428y}, abstractNote={The promise of molecular electronics has stimulated a variety of approaches for making hybrid junctions wherein molecules are sandwiched between two metal contacts or a metal and a semiconductor contact. However, the fate of molecules subsequent to deposition of a top metal contact has generally not been well characterized. Toward this goal, the interaction of evaporated Cu, Ag, and Au films deposited in varying thicknesses (3, 5, and 8 nm) on a series of monolayer-coverage porphyrins covalently attached to Si(100) substrates was investigated. Each porphyrin contains a triallyl tripod attached to the porphyrin via a p-phenylene unit, which anchors the porphyrin to the Si(100) substrate via hydrosilylation of the allyl groups. All of the porphyrins are Zn chelates bearing meso p-tolyl substituents orthogonal (lateral) to the tripodal surface anchor, but contain different substituents in the meso position opposite (distal) to the surface anchor, p-tolyl, α,α,α-trifluoro-p-tolyl, pentafluorophenyl, or p-cyan...}, number={25}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Anariba, Franklin and Tiznado, Hugo and Diers, James R. and Schmidt, Izabela and Muresan, Ana Z. and Lindsey, Jonathan S. and Zaera, Francisco and Bocian, David F.}, year={2008}, month={Jun}, pages={9474–9485} }
 @article{anariba_schmidt_muresan_lindsey_bocian_2008, title={Metal-molecule interactions upon deposition of copper overlayers on reactively functionalized porphyrin monolayers on Si(100)}, volume={24}, ISSN={["0743-7463"]}, DOI={10.1021/la800472c}, abstractNote={The interaction of evaporated Cu deposited on a series of porphyrins in monolayers covalently attached to Si(100) substrates was investigated using cyclic voltammetry and FTIR spectroscopy. Each porphyrin contains a triallyl tripod attached to the porphyrin via a p-phenylene unit. The tripod anchors the porphyrin to the Si(100) substrate via hydrosilylation of the allyl groups. Two of the porphyrins are Zn chelates that possess meso p-cyanophenyl substituentsone, ZnP-CND, contains a single group opposite (distal) to the tripodal surface anchor, whereas the other, ZnP-CNL, contains two groups orthogonal (lateral) to the surface anchor. A third Zn porphyrin, ZnP, containing nonreactive p-tolyl groups at all three nonanchoring meso positions, was examined for comparison. The fourth porphyrin, FbP-HD, is a metal-free species (free base) that contains nonreactive phenyl (distal) and p-tolyl groups (lateral) at the three nonanchoring meso positions. The fifth porphyrin, CuP-HD, is the Cu chelate of FbP-HD, and serves as a reference complex for evaluating the effects of Cu metal deposition onto FbP-HD. The studies indicate that all of the porphyrin monolayers are robust under the conditions of Cu deposition, experiencing no noticeable degradation. In addition, the Cu metal does not penetrate through the monolayer to form electrically conductive filaments. For the ZnP-CND monolayers, the deposited Cu quantitatively reacts/complexes with the distal cyano group. In contrast, for the ZnP-CNL monolayers no reaction/complexation of the lateral cyano groups is observed. For the FbP-HD monolayers, Cu deposition results in quantitative insertion of Cu into the free base porphyrin. Collectively, the studies demonstrate that porphyrin monolayers are amenable to direct deposition of Cu overlayers and that functionalization of the porphyrins can be used to mediate the attributes of the metal-molecule junction.}, number={13}, journal={LANGMUIR}, author={Anariba, Franklin and Schmidt, Lzabela and Muresan, Ana Z. and Lindsey, Jonathan S. and Bocian, David F.}, year={2008}, month={Jul}, pages={6698–6704} }
 @article{jiao_thamyongkit_schmidt_lindsey_bocian_2007, title={Characterization of porphyrin surface orientation in monolayers on au(111) and si(100) using spectroscopically labeled molecules}, volume={111}, ISSN={["1932-7447"]}, DOI={10.1021/jp073824c}, abstractNote={The synthesis and surface IR characterization are reported for a series of porphyrins bearing vibrational spectroscopic labels that afford distinction of the two in-plane axes of the porphyrin ring. The labeled porphyrins include three different types of tethers for surface attachment, those containing either methylthio (−CH2S−) or benzylthio (−BzS−) for attachment to either Au or Si and a tripodal alkenyl group for attachment to Si. The spectroscopic labels are placed so as to enable distinction between the methyl group of a p-tolyl substituent that lies along the molecular axis distal to the tether versus the p-tolyl substituents that lie along the orthogonal in-plane axis lateral to the tether. The porphyrins include isotopically labeled species containing CD3 and species wherein a CF3 replaces CH3. The spectroscopically labeled molecules allow evaluation of both the tilt angle (θ) with respect to the surface normal and the rotation angle (φ) about the molecular axis. These two angles cannot be uniquel...}, number={34}, journal={JOURNAL OF PHYSICAL CHEMISTRY C}, author={Jiao, Jieying and Thamyongkit, Patchanita and Schmidt, Izabela and Lindsey, Jonathan S. and Bocian, David F.}, year={2007}, month={Aug}, pages={12693–12704} }
 @article{muthiah_taniguchi_kim_schmidt_kee_holten_bocian_lindsey_2007, title={Synthesis and photophysical characterization of porphyrin, chlorin and bacteriochlorin molecules bearing tethers for surface attachment}, volume={83}, ISSN={["0031-8655"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-36248978026&partnerID=MN8TOARS}, DOI={10.1111/j.1751-1097.2007.00195.x}, abstractNote={Abstract}, number={6}, journal={PHOTOCHEMISTRY AND PHOTOBIOLOGY}, publisher={Wiley}, author={Muthiah, Chinnasamy and Taniguchi, Masahiko and Kim, Han-Je and Schmidt, Izabela and Kee, Hooi Ling and Holten, Dewey and Bocian, David F. and Lindsey, Jonathan S.}, year={2007}, pages={1513–1528} }
 @article{kulikov_schmidt_muresan_lee_bocian_lindsey_2007, title={Synthesis of porphyrins for metal deposition studies in molecular information storage applications}, volume={11}, ISSN={["1099-1409"]}, DOI={10.1142/S1088424607000801}, abstractNote={ Porphyrins may serve as the active charge-storage medium in memory chips. A series of 14 porphyrins (trans-A2B2, trans-AB2C, or A4 type; free base, copper or zinc chelate) has been synthesized for investigation of metal deposition on porphyrin monolayers. Each trans-AB2C porphyrin is equipped with a surface attachment group and a distal functional group (or flanking functional groups). The surface attachment groups include S-acetylthiomethyl, hydroxymethyl, TMS-ethynyl, allyl, and triallylmethyl; the functional groups include amino, cyano, dipyrrin-5-yl, formyl, and nitro; all of which are attached to the p-position of a porphyrin meso-phenyl group. Two non-redox-active triallylmethyl-substituted arenes were also prepared for use as control compounds. }, number={10}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Kulikov, Oleg V. and Schmidt, Izabela and Muresan, Ana Z. and Lee, Marcia A. -P. and Bocian, David F. and Lindsey, Jonathan S.}, year={2007}, pages={699–712} }
 @article{lysenko_thamyongkit_schmidt_diers_bocian_lindsey_2006, title={Diverse porphyrin dimers as candidates for high-density charge-storage molecules}, volume={10}, ISSN={["1099-1409"]}, DOI={10.1142/S1088424606000041}, abstractNote={ Porphyrinic molecules have been shown to be viable candidates for a molecular-based information storage medium on the basis of redox activity. An optimal redox-based information storage medium requires a large charge density in the molecular footprint on the anchoring substrate. The use of dimeric versus monomeric architectures affords one route to achieving increased charge density without sacrificing surface cross sectional area. Towards this goal, a series of zinc and cobalt containing porphyrin dimers has been prepared and characterized. The interporphyrin linkages in the dimers include p-phenylene, ethynyl, 1,4-butadiynyl, and ethynylphenylethynyl joining porphyrin meso-positions; Crossley-type fusion bridging porphyrin β-positions, and Osuka-type triple fusions bridging one meso- and two β-positions. The electrochemical features of each dimer have been evaluated. }, number={1}, journal={JOURNAL OF PORPHYRINS AND PHTHALOCYANINES}, author={Lysenko, Andrey B. and Thamyongkit, Patchanita and Schmidt, Izabela and Diers, James R. and Bocian, David F. and Lindsey, Jonathan S.}, year={2006}, pages={22–32} }
 @article{schmidt_jiao_thamyongkit_sharada_bocian_lindsey_2006, title={Investigation of stepwise covalent synthesis on a surface yielding porphyrin-based multicomponent architectures}, volume={71}, ISSN={["0022-3263"]}, DOI={10.1021/jo052650x}, abstractNote={Porphyrins have been shown to be a viable medium for use in molecular-based information storage applications. The success of this application requires the construction of a stack of components ("electroactive surface/tether/charge-storage molecule/linker/electrolyte/top contact") that can withstand high-temperature conditions during fabrication (up to 400 degrees C) and operation (up to 140 degrees C). To identify suitable chemistry that enables in situ stepwise synthesis of covalently linked architectures on an electroactive surface, three sets of zinc porphyrins (22 altogether) have been prepared. In the set designed to form the base layer on a surface, each porphyrin incorporates a surface attachment group (triallyl tripod or vinyl monopod) and a distal functional group (e.g., pentafluorophenyl, amine, bromo, carboxy) for elaboration after surface attachment. A second set designed for in situ dyad construction incorporates a single functional group (alcohol, isothiocyanato) that is complementary to the functional group in the base porphyrins. A third set designed for in situ multad construction incorporates two identical functional groups (bromo, alcohol, active methylene, amine, isothiocyanato) in a trans configuration (5,15-positions in the porphyrin). Each porphyrin that bears a surface attachment group was found to form a good quality monolayer on Si(100) as evidenced by the voltammetric and vibrational signatures. One particularly successful chemistry identified for stepwise growth entailed reaction of a surface-tethered porphyrin-amine with a dianhydride (e.g., 3,3',4,4'-biphenyltetracarboxylic dianhydride), forming the monoimide/monoanhydride. Subsequent reaction with a diamine (e.g., 4,4'-methylene-bis(2,6-dimethylaniline)) gave the bis(imide) bearing a terminal amine. Repetition of this stepwise growth process afforded surface-bound oligo-imide architectures composed of alternating components without any reliance on protecting groups. Taken together, the ability to prepare covalently linked constructs on a surface without protecting groups in a stepwise manner augurs well for the systematic preparation of a wide variety of functional molecular devices.}, number={8}, journal={JOURNAL OF ORGANIC CHEMISTRY}, author={Schmidt, I and Jiao, JY and Thamyongkit, P and Sharada, DS and Bocian, DF and Lindsey, JS}, year={2006}, month={Apr}, pages={3033–3050} }
 @article{jiao_anariba_tiznado_schmidt_lindsey_zaera_bocian_2006, title={Stepwise formation and characterization of covalently linked multiporphyrin-imide architectures on Si(100)}, volume={128}, ISSN={["1520-5126"]}, DOI={10.1021/ja060906q}, abstractNote={A major challenge in molecular electronics and related fields entails the fabrication of elaborate molecular architectures on electroactive surfaces to yield hybrid molecular/semiconductor systems. A method has been developed for the stepwise synthesis of oligomers of porphyrins linked covalently via imide units. A triallyl-porphyrin bearing an amino group serves as the base unit on Si(100), and the alternating use of a dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) and a porphyrin-diamine for reaction enables the rapid and simple buildup of oligomers composed of 2-5 porphyrins. The properties of these porphyrin "multad" films on Si(100) were interrogated using a variety of techniques. The charge densities of the redox-active porphyrin oligomers were determined via electrochemical methods. The stepwise growth was evaluated in detail via Fourier transform infrared (FTIR) spectroscopy and by selected X-ray photoelectron spectroscopic (XPS) studies. The morphology was probed via AFM methods. Finally, the thickness was evaluated by using a combination of ellipsometry and AFM height profiling, accompanied by selected XPS studies. Collectively, these studies demonstrate that high charge density, ultrathin, multiporphyrin films of relatively well-controlled thickness can be grown in a stepwise fashion using the imide-forming reaction. The increased charge densities afforded by the porphyrin multads may prove important for the fabrication of molecular-based information-storage devices. This bottom-up process for construction of surface-tethered molecular architectures complements the top-down lithographic approach for construction of functional devices with nanoscale dimensions.}, number={21}, journal={JOURNAL OF THE AMERICAN CHEMICAL SOCIETY}, author={Jiao, Jieying and Anariba, Franklin and Tiznado, Hugo and Schmidt, Izabela and Lindsey, Jonathan S. and Zaera, Francisco and Bocian, David F.}, year={2006}, month={May}, pages={6965–6974} }
 @article{liu_schmidt_thamyongkit_loewe_syomin_diers_zhao_misra_lindsey_bocian_2005, title={Synthesis and Film-Forming Properties of Ethynylporphyrins}, volume={17}, ISSN={0897-4756 1520-5002}, url={http://dx.doi.org/10.1021/cm047858y}, DOI={10.1021/cm047858y}, abstractNote={Thermal treatment of ethynyl porphyrin monomers on a surface has been found to yield robust porphyrin films. The scope of this in situ polymerization has been surveyed by the synthesis and characterization of a collection of 20 zinc porphyrins bearing diverse patterns of 1−4 ethyne (or protected ethyne) groups and a variety of nonlinking substituents. Films have been prepared on Si(100), SiO2, Au(111), and glass. The films prepared on Si(100) have been examined by electrochemical methods, which indicate that surface coverages 50-fold greater than those of saturation-coverage monolayers are achievable, although the coverage varies appreciably (10-fold) among the survey group of molecules under a controlled set of film-forming conditions. Variation in these conditions affords control over the number of layers in the film (from a few to tens or more). The electrochemical characteristics of the multilayer films further indicate that the redox thermodynamics are of comparable homogeneity to those of monolayers...}, number={14}, journal={Chemistry of Materials}, publisher={American Chemical Society (ACS)}, author={Liu, Zhiming and Schmidt, Izabela and Thamyongkit, Patchanita and Loewe, Robert S. and Syomin, Dennis and Diers, James R. and Zhao, Qian and Misra, Veena and Lindsey, Jonathan S. and Bocian, David F.}, year={2005}, month={Jul}, pages={3728–3742} }