ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOrientation Control of Functional Molecules in Langmuir-Blodgett Films Caused by a Trigger Molecule: Infrared Spectroscopic Study on the Orientation of n-Alkane, Trigger MoleculeReiko Azumi, Mutsuyoshi Matsumoto, Shin-ichi Kuroda, and Maxwell J. CrossleyCite this: Langmuir 1995, 11, 11, 4495–4498Publication Date (Print):November 1, 1995Publication History Published online1 May 2002Published inissue 1 November 1995https://pubs.acs.org/doi/10.1021/la00011a052https://doi.org/10.1021/la00011a052research-articleACS PublicationsRequest reuse permissionsArticle Views95Altmetric-Citations27LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Treatment of meso- or β-nitroporphyrins with deuteriated lithium hydroxide and [N,N,S-2H3]2-aminobenzenethiol in dry N,N-dimethylformamide results in replacement of the nitro group with deuterium; the regiospecificity of the process is demonstrated by synthesis of [20-2H1]mesoporphyrin IX dimethyl ester.
Multiple photosynthetic reaction centers have successfully been constructed using a supramolecular complex of zinc porphyrin dendrimer [D(ZnP) 16 ] with pyridylnaphthalenediimide (PyNIm) in benzonitrile. The apparent formation constant determined from the fluorescence quenching of the singlet excited state of porphyrin moieties by PyNIm is significantly larger than that determined from the UV-vis spectral change. This indicates that efficient energy migration occurs between the porphyrin units of the dendrimer prior to the electron transfer from the singlet excited state of zinc porphyrin to PyNIm. The charge-separated (CS) state has been successfully detected as the transient absorption spectrum in the laser flash photolysis. The CS lifetime of in the supramolecular complex of D(ZnP) 16 with PyNIm was determined to be 0.83 ms at 298 K.
We demonstrate that systematic errors can be reduced and physical insight gained through investigation of the dependence of free energies for meso-tetraalkylporphyrin self-assembled monolayers (SAMs) polymorphism on the alkyl chain length m. These SAMs form on highly ordered pyrolytic graphite (HOPG) from organic solution, displaying manifold densities and atomic structures. SAMs with m = 11–19 are investigated experimentally while those with m = 6–28 are simulated using density-functional theory (DFT). It is shown that, for m = 15 or more, the alkyl chains "crystallize" to dominate SAM structure. Meso-tetraalkylporphyrin SAMs of length less than 11 have never been observed, a presumed effect of inadequate surface attraction. Instead, we show that free energies of SAM formation actually enhance as the chain length decreases. The inability to image regular SAMs stems from the appearance of many polymorphic forms of similar free energy, preventing SAM ordering. We also demonstrate a significant odd/even effect in SAM structure arising from packing anomalies. Comparison of the chain-length dependence of formation free energies allows the critical dispersion interactions between molecules, solvent, and substrate to be directly examined. Interpretation of the STM data combined with measured enthalpies indicates that Grimme's "D3" explicit-dispersion correction and the implicit solvent correction of Floris, Tomasi and Pascual Ahuir are both quantitatively accurate and very well balanced to each other.
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An optical fiber acid-sensor based on protonation of a porphyrin solution within a single-hole structured optical fiber is proposed and demonstrated. The liquid-core fiber acts as a microcell reactor, and changes in the spectral signature with acidification are detected. Challenges and limitations in the practical deployment of such sensors are evaluated. An effective chemical sensor is demonstrated, but issues such as diffusion limit its full utilization. Some solutions are discussed.
The porous properties of self-assembled waveguides made up of nanoparticles are characterised. Atomic force microscopy (AFM) reveals predominantly hcp or fcc packing suggesting a remarkably well ordered and distributed porous structure. N2 adsorption studies estimate a surface area SA ~ 101 m2/g, a total interstitial volume Vi ~ 1.7 mL/g and a pore size distribution of r ~ (2 - 6) nm. This distribution is in excellent agreement with the idealised values for identically sized particles obtained for the octahedral and tetrahedral pores of the hcp and fcc lattices, estimated to lie within and rtet ~ (2.2 – 3.3) nm and roct ~ (4.2 – 6.2) nm for particles varying in size over 20 to 30 nm. Optical transmission based percolation studies reveal rapid penetration of Rhodamine dye (< 5 s) with very little percolation of larger molecules such as ZnTPP observed under similar loading conditions. In the latter case, laser ablation was used to determine the transport of hydrated Zn2+ to be D ~ 3 x 10-4 nm2s-1. By comparison, ZnTPP was not able to percolate into the wire over the time of exposure, t = 10 mins, effectively demonstrating the self-assembled structure acting as a molecular sieve. We discuss the potential of such structures more broadly and conclude that the controllable distribution of such nano-chambers offers the possibility of amplifying, or up-scaling, an otherwise local interaction or nanoreactions to make detection and diagnostics much simpler; it also opens up a new approach to material engineering making new composites with periodic nanoscale variability. These and other unique aspects of these structures are embodied in an overall concept of lab-in-wire, or similar self-assembled structures, extending our previous concept of lab-in-fibre from the micro domain into the nano domain.
Periodontal disease is an inflammatory process affecting supporting tissues surrounding the teeth. The anaerobic Gram-negative bacterium Porphyromonas gingivalis is implicated in the disease. This organism requires the uptake of porphyrins most apparently as haem 1 from local haemorrhage and it has a HA2 receptor on the outer membrane for this purpose that provides the opportunity to achieve selective anti-microbial activity. Uniquely, this receptor is based on recognition of porphyrin macrocycle and on a propionic acid side-chain rather than recognition of the coordinated metal ion through chelation, a process used by other organisms with the HasA porphyrin receptor. Porphyrin–antibiotic conjugates 11, 12, 13a and 13b were designed as potential highly selective P. gingivalisinhibitors, a key point being that they are based on the use of free-base porphyrins to render them unpalatable to other organisms. These compounds were synthesised from metronidazole 4 and deuteroporphyrin IX 3. Conjugates 11, 12, 13a and 13b are all recognised by the HA2 receptor of P. gingivalis, bind as strongly as haem 1 to HA2 and are highly effective. For example, the amide-linked mono-metronidazole mono-acid adducts 11 and 12 have the same growth inhibitory activity towards P. gingivalis and both are two-fold more active than metronidazole 4 and ten- to twenty-fold more effective than the metronidazole derivative, amine 5. The methyl esters 9 and 10, in contrast, are not recognised by HA2 and are ineffective in inhibiting P. gingivalis, leading to the conclusion that capture by HA2 may be necessary for activity of the adducts. Preliminary growth inhibition assays involving a range of bacteria have demonstrated the high selectivity of conjugates 13a and 13b towards P. gingivalis.
The atomic structure of the chains of an alkyl porphyrin (5,10,15,20-tetranonadecylporphyrin) self-assembled monolayer (SAM) at the solid/liquid interface of highly ordered pyrolytic graphite (HOPG) and 1-phenyloctane is resolved using calibrated scanning tunneling microscopy (STM), density functional theory (DFT) image simulations, and ONIOM-based geometry optimizations. While atomic structures are often readily determined for porphyrin SAMs, the determination of the structure of alkyl-chain connections has not previously been possible. A graphical calibration procedure is introduced, allowing accurate observation of SAM lattice parameters, and, of the many possible atomic structures modeled, only the lowest-energy structure obtained was found to predict the observed lattice parameters and image topography. Hydrogen atoms are shown to provide the conduit for the tunneling current through the alkyl chains.
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