- Sequence and Structure of Peptoid Oligomers Can Tune the Photoluminescence of an Embedded Ruthenium Dye
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The understanding of structure–function relationships within synthetic biomimetic systems is a fundamental challenge in chemistry. Herein we report the direct correlation between the structure of short peptoid ligands—N-substituted glycine oligomers incorporating 2,2′-bipyridine groups—varied in their monomer sequence, and the photoluminescence of RuII centers coordinated by these ligands. Based on circular dichroism and fluorescence spectroscopy we demonstrate that while helical peptoids do not affect the fluorescence of the embedded RuII chromophore, unstructured peptoids lead to its significant decay. Transmittance electron microscopy (TEM) revealed significant differences in the arrangements of metal-bound helical versus unstructured peptoids, suggesting that only the latter can have through-space interactions with the ruthenium dye leading to its quenching. High-resolution TEM enabled the remarkable direct imaging of singular ruthenium-bound peptoids and bundles, supporting our explanation for structure-depended quenching. Moreover, this correlation allowed us to fine-tune the luminescence properties of the complexes simply by modifying the sequence of their peptoid ligands. Finally, we also describe the chiral properties of these Ru–peptoids and demonstrate that remote chiral induction from the peptoids backbone to the ruthenium center is only possible when the peptoids are both chiral and helical.
- Zborovsky, Lieby,Tigger-Zaborov, Hagar,Maayan, Galia
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- New Ru(II)/Os(II)-polypyridyl complexes for coupling to TiO2 surfaces through acetylacetone functionality and studies on interfacial electron-transfer dynamics
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New Ru(II)- and Os(II)-polypyridyl complexes have been synthesized with pendant acetylacetone (acac) functionality for anchoring on nanoparticulate TiO2 surfaces with a goal of developing an alternate sensitizer that could be utilized for designing an efficient dye-sensitized solar cell (DSSC). Time-resolved transient absorption spectroscopic studies in the femtosecond time domain have been carried out. The charge recombination rates are observed to be very slow, compared with those for strongly coupled dye molecules having catechol as the anchoring functionality. The results of such studies reveal that electron-injection rates from the metal complex-based LUMO to the conduction band of TiO2 are faster than one would expect for an analogous complex in which the chromophoric core and the anchoring moiety are separated with multiple saturated C-C linkages. Such an observation is rationalized based on computational studies, and a relatively smaller spatial distance between the dye LUMO and the TiO2 surface accounted for this. Results of this study are compared with those for analogous complexes having a gem-dicarboxy group as the anchoring functionality for covalent binding to the TiO2 surface to compare the role of binding functionalities on electron-transfer dynamics. the Partner Organisations 2014.
- Banerjee, Tanmay,Biswas, Abul Kalam,Sahu, Tuhin Subhra,Ganguly, Bishwajit,Das, Amitava,Ghosh, Hirendra Nath
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- Supramolecular Control of Charge-Transfer Dynamics on Dye-sensitized Nanocrystalline TiO2 Films
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A [Ru(dcbpy)2(NCS)2 dye has been chemically modified by the addition of a secondary electron donor moiety, N,N-(di-p-anisylamino)phenoxymethyl. Optical excitation of the modified dye adsorbed to nanocrystalline TiO2 films
- Hirata, Narukuni,Lagref, Jean-Jacques,Palomares, Emilio J.,Durrant, James R.,Nazeeruddin, M. Khaja,Gratzel, Michael,Di Censo, Davide
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- Using intramolecular energy transfer to transform non-photoactive, visible-light-absorbing chromophores into sensitizers for photoredox reactions
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This work discusses the synthesis, photophysical behavior, and photoinduced electron-transfer reactivity of multichromophoric molecules having a visible-light-absorbing MLCT component coupled to a ligand with a localized excited state of the same spin multiplicity that serves to lengthen the excited-state lifetime of the complex significantly. The appropriate ligands were prepared by Wittig coupling of a bipyridine derivative with pyrenecarboxaldehyde. The modified ligand, a pyrene-vinyl-bipyridyl ensemble (pyrv-bpy), was then reacted with RuCl3 to yield [(pyrv-bpy) 2RuCl2]. The complex has MLCT absorption out to 800 nm, and excitation results in the formation of a ligand-localized excited state with a lifetime long enough to undergo bimolecular electron-transfer reactions. The pyrenylvinyl "localized" excited state of the complex reacts via photoinduced electron transfer with a variety of viologen and diquat electron acceptors. The remarkable aspect of the electron-transfer process is that whereas the excited state can be considered to be ligand-localized the photoredox reaction almost certainly involves the direct formation of the one-electron-oxidized metal center.
- Gu, Jing,Chen, Jin,Schmehl, Russell H.
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- Mechanochemical Release of Non-Covalently Bound Guests from a Polymer-Decorated Supramolecular Cage
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Supramolecular coordination cages show a wide range of useful properties including, but not limited to, complex molecular machine-like operations, confined space catalysis, and rich host–guest chemistries. Here we report the uptake and release of non-covalently encapsulated, pharmaceutically-active cargo from an octahedral Pd cage bearing polymer chains on each vertex. Six poly(ethylene glycol)-decorated bipyridine ligands are used to assemble an octahedral PdII6(TPT)4 cage. The supramolecular container encapsulates progesterone and ibuprofen within its hydrophobic nanocavity and is activated by shear force produced by ultrasonication in aqueous solution entailing complete cargo release upon rupture, as shown by NMR and GPC analyses.
- G?stl, Robert,Küng, Robin,Pausch, Tobias,Rasch, Dustin,Schmidt, Bernd M.
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supporting information
p. 13626 - 13630
(2021/05/10)
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- Light-Activated Electron Transfer and Turnover in Ru-Modified Aldehyde Deformylating Oxygenases
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Conversion of biological molecules into fuels or other useful chemicals is an ongoing chemical challenge. One class of enzymes that has received attention for such applications is aldehyde deformylating oxygenase (ADO) enzymes. These enzymes convert aliphatic aldehydes to the alkanes and formate. In this work, we prepared and investigated ADO enzymes modified with RuII(tris-diimine) photosensitizers as a starting point for probing intramolecular electron transfer events. Three variants were prepared, with RuII-modification at the wild type (WT) residue C70, at the R62C site in one mutant ADO, and at both C62 and C70 in a second mutant ADO protein. The single-site modification of WT ADO at C70 using a cysteine-reactive label is an important observation and opens a way forward for new studies of electron flow, mechanism, and redox catalysis in ADO. These Ru-ADO constructs can perform the ADO catalytic cycle in the presence of light and a sacrificial reductant. In this work, the Ru photosensitizer serves as a tethered, artificial reductase that promotes turnover of aldehyde substrates with different carbon chain lengths. Peroxide side products were detected for shorter chain aldehydes, concomitant with less productive turnover. Analysis using semiclassical electron transfer theory supports proposals for hopping pathway for electron flow in WT ADO and in our new Ru-ADO proteins.
- Bains, Rajneesh K.,Miller, Jessica J.,Van Der Roest, Hannah K.,Qu, Sheng,Lute, Brad,Warren, Jeffrey J.
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supporting information
p. 8211 - 8217
(2018/07/25)
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- Optically Reconfigurable Monolayer of Azobenzene Donor Molecules on Oxide Surfaces
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The structural configuration of molecules assembled at organic-inorganic interfaces within electronic materials strongly influences the functional electronic and vibrational properties relevant to applications ranging from energy storage to photovoltaics.
- McElhinny, Kyle M.,Huang, Peishen,Joo, Yongho,Kanimozhi, Catherine,Lakkham, Arunee,Sakurai, Kenji,Evans, Paul G.,Gopalan, Padma
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p. 2157 - 2168
(2017/03/16)
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- Ion Pair-Directed Regiocontrol in Transition-Metal Catalysis: A Meta-Selective C-H Borylation of Aromatic Quaternary Ammonium Salts
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The use of noncovalent interactions to direct transition-metal catalysis is a potentially powerful yet relatively underexplored strategy, with most investigations thus far focusing on using hydrogen bonds as the controlling element. We have developed an ion pair-directed approach to controlling regioselectivity in the iridium-catalyzed borylation of two classes of aromatic quaternary ammonium salts, leading to versatile meta-borylated products. By examining a range of substituted substrates, this provides complex, functionalized aromatic scaffolds amenable to rapid diversification and more broadly demonstrates the viability of ion-pairing for control of regiochemistry in transition-metal catalysis.
- Davis, Holly J.,Mihai, Madalina T.,Phipps, Robert J.
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supporting information
p. 12759 - 12762
(2016/10/13)
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- Artificial photosynthesis dendrimers integrating light-harvesting, electron delivery and hydrogen production
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A series of artificial photosynthesis complexes, Gn-Ir-Hy (n = 1-4), were constructed by attaching iridium complexes and [Fe-Fe]-hydrogenase mimic to the periphery and core, respectively, of poly(aryl ether) dendrimers of different generations. The iridium complexes act as the light-harvesting antennae and the hydrogenase mimic core is the catalytic center. Light-harvesting, photoinduced electron-transfer, and hydrogen photochemical production were hierarchically realized within the dendritic photosynthesis mimics using triethylamine as the sacrificial electron donor. The catalytic activity is enhanced as the generation of dendritic catalysts increases, and the turnover number for generation 4 is nearly 4 times more than that of generation 1. The peripheral antennae not only harvest photons but also act as electronic energy reservoirs for the photochemical production, which facilitates the catalytic process together with the increased light-harvesting and protection effects of dendritic frameworks. Therefore, efficient artificial photosynthesis systems with complete light-harvesting and catalytic functions can be advanced with such rational design.
- Xun, Zhiqing,Yu, Tianjun,Zeng, Yi,Chen, Jinping,Zhang, Xiaohui,Yang, Guoqiang,Li, Yi
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supporting information
p. 12965 - 12971
(2015/06/25)
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- Squaraine-sensitized composite of a reduced graphene oxide/Tio2 photocatalyst π Stacking as a new method of dye anchoring
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We synthesized a near infra-red (NIR)-absorbing squaraine dye (VJ-S) showing strong absorption and emission maxima at 684 and 704 nm, respectively, with a high molar extinction coefficient (ε) of 1.277 × 105 M-1 cm-1 and a band gap of 1.77 eV. Its oxidation and reduction potentials were found to be 0.889 and -0.795 V, respectively, with HOMO and LUMO levels of -5.21 and -3.53 eV, respectively. We also prepared the self-assembled core/shell nanocomposite r-NGOT, where TiO2 is the core and reduced nano-sized graphene oxide (r-NGO) is the shell. When VJ-S was anchored on r-NGOT, it showed π-π stacking with r-NGO, which is confirmed by Fourier-transformed infrared spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and electron energy loss spectroscopy. The optical absorption spectrum of the VJ-S/r-NGOT nanocomposite measured with diffuse reflectance UV/visible absorption spectroscopy covers the whole range of visible light wavelengths up to 800 nm. The photocatalytic activity of VJ-S/r-NGOT at visible light wavelengths (λ > 420 nm) is much higher than that of r-NGOT alone. This journal is
- Joseph, K. L. Vincent,Lim, Jonghun,Anthonysamy,Kim, Hyoung-Il,Choi, Wonyong,Kim, Jin Kon
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p. 232 - 239
(2015/02/18)
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- New imaging reagents for lipid dense regions in live cells and the nucleus in fixed MCF-7 cells
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Two new uracil (U) and 5-flurouracil (5-FU) labeled ruthenium(II)-polypyridyl based cellular imaging reagents are reported. Confocal laser scanning microscopic images with live and paraformaldehyde (PFA) fixed MCF-7 cells are examined using these two low-cytotoxic reagents. Experimental results show that these two complexes, appropriately functionalized with U (1) and 5-FU (2), have specific affinity for the lipid dense regions like the endoplasmic reticulum, cell membrane, and cytoplasmic vacuoles in live MCF-7 cells, and dye internalization in these regions happened following an endocytosis pathway. Interestingly, these two complexes are found to be localized in the nucleus of the PFA fixed cells. For fixed cells, presumably the lipid layer disruption helped in the explicit localization of the complexes 1 and 2 in the cell nucleus through specific interaction with cellular DNA. Poor and non-specific internalization of an analogous model complex 3, without having a U or 5-FU moiety, reveals the definite influence of U or 5-FU as well as the role of lipophilicity of the respective complex 1 and 2 in the cellular internalization process. Apart from these, a large Stokes shift (～160 nm) and an appreciably long lived 3MLCT excited state (～320 ns) in aq. buffer medium (pH 7.4) are other key features for complexes 1 and 2. Unlike the common nuclear DNA staining reagents like DAPI, these low-cytotoxic reagents are found to be highly stable towards photo-bleaching upon irradiation with 455 nm at the MLCT band for these complexes.
- Ramu, Vadde,Ali, Firoj,Taye, Nandaraj,Garai, Bikash,Alam, Aftab,Chattopadhyay, Samit,Das, Amitava
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supporting information
p. 7177 - 7185
(2015/09/21)
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- Layered γ-zirconium phosphate intercalated with Ru(bpy)3-viologen dyads as unusual materials for dye-sensitised solar cells: Improving efficiency by double sensitisation
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The intercalation materials prepared from the laminar salt α-zirconium phosphate and various dyads formed from Ru (bpy)3 and viologens were tested as photoactive components in dye-sensitised solar cells. The efficiencies significantly increased, up to 0.2 %, when the materials were treated with the panchromatic N535 dye. A mechanism for this double sensitisation process is proposed, which should enable further improvement of these α-ZrP-based materials as a reasonable alternative to the usual Ti-based dye-sensitised solar cells. CSIRO 2014.
- De Victoria-Rodriguez, Maria,Atienzar, Pedro,Juanes, Olga,Rodriguez-Ubis, Juan Carlos,Brunet, Ernesto,Garcia, Hermenegildo
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p. 389 - 397
(2014/04/03)
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- Bifunctional mesoporous silica nanoparticles as cooperative catalysts for the Tsuji-Trost reaction-tuning the reactivity of silica nanoparticles
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Bifunctional mesoporous silica nanoparticles (MSNs) bearing Pd-complexes and additional basic sites were prepared and tested as cooperative active catalysts in the Tsuji-Trost allylation of ethyl acetoacetate. Functionalization of the MSNs was realized by postmodification using click-chemistry. The selectivity of mono versus double allylation was achieved by control of reaction temperature and the nature of the catalyst.
- Dickschat, Arne T.,Behrends, Frederik,Surmiak, Sabrina,Wei?, Mark,Eckert, Hellmut,Studer, Armido
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p. 2195 - 2197
(2013/03/29)
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- Photocatalytic conversion of CO2 to CO using rhenium bipyridine platforms containing ancillary phenyl or BODIPY moieties
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Harnessing of solar energy to drive the reduction of carbon dioxide to fuels requires the development of efficient catalysts that absorb sunlight. In this work, we detail the synthesis, electrochemistry, and photophysical properties of a set of homologous fac-ReI(CO)3 complexes containing either an ancillary phenyl (8) or BODIPY (12) substituent. These studies demonstrate that both the electronic properties of the rhenium center and BODIPY chromophore are maintained for these complexes. Photolysis studies demonstrate that both assemblies 8 and 12 are competent catalysts for the photochemical reduction of CO2 to CO in dimethylformamide (DMF) using triethanolamine (TEOA) as a sacrificial reductant. Both compounds 8 and 12 display turnover frequencies (TOFs) for photocatalytic CO production upon irradiation with light (λex ≥ 400 nm) of ～5 h -1 with turnover number (TON) values of approximately 20. Although structural and photophysical measurements demonstrate that electronic coupling between the BODIPY and fac-ReI(CO)3 units is limited for complex 12, this work clearly shows that the photoactive BODIPY moiety is tolerated during catalysis and does not interfere with the observed photochemistry. When taken together, these results provide a clear roadmap for the development of advanced rhenium bipyridine complexes bearing ancillary BODIPY groups for the efficient photocatalytic reduction of CO2 using visible light.
- Andrade, Gabriel A.,Pistner, Allen J.,Yap, Glenn P. A.,Lutterman, Daniel A.,Rosenthal, Joel
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p. 1685 - 1692
(2013/09/02)
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- Synthesis and spectral properties of ruthenium(II) complexes based on 2,2′-bipyridines modified by a perylene chromophore
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Five new 2,2′-bipyridines functionalized with a perylene or a perylenediimide moiety were synthesized and the corresponding heteroleptic ruthenium(II) complexes ([Ru(bpy)2(L)](PF6)2; bpy = 2,2′-bipyridyl, L = perylene-substituted bpy ligand) were prepared. The UV-vis spectra of the ruthenium(II) complexes showed red-shifted and intense absorption bands derived from the conjugated structure of the new ligands.
- Kodama, Koichi,Kobayashi, Akinori,Hirose, Takuji
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supporting information
p. 5514 - 5517
(2013/09/23)
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- NOBLE RUTHENIUM-TYPE SENSITIZERS AND METHOD OF PREPARING THE SAME
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The present invention relates to a noble ruthenium-type dye and a making method thereof, and more particularly, to a noble ruthenium- type dye(sensitizer) which is used to manufacture a dye-sensitized solar cell, drastically improves a photoelectric conve
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Page/Page column 26; 28-29
(2008/12/08)
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- Metal ion induced allosteric transition in the catalytic activity of an artificial phosphodiesterase
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An artificial phosphodiesterase (1) bearing two types of metal binding sites, a catalytic site and a regulatory bipyridine site showed a unique allosteric transition in the catalytic activity against the metal concentration. The rate constants for the hydrolysis reaction of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNP) and RNA dimer (ApA) with and without an effector metal ion were evaluated; the kobs value of HPNP hydrolysis for 1?(Zn 2+)3 (2.0 × 10-4 s-1) is 3.3 times larger than that for 1?(Zn2+)2. In the case of 1 and Cu2+, a 19.4 times larger kobs value was obtained for 1?(Cu2+)3 (1.2 × 10-3 s -1) against 1?(Cu2+)2. The increase in the catalytic activity is ascribed to the allosteric conformational transition of 1 induced by the coordination of effector metal ion to the Bpy moiety. A detailed investigation revealed that a conformational change of 1 induced by the third M2+ complexation enhances the rate of hydrolysis rather than a change in the substrate affinity. The Royal Society of Chemistry 2008.
- Takebayashi, Shinji,Shinkai, Seiji,Ikeda, Masato,Takeuchi, Masayuki
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experimental part
p. 493 - 499
(2008/10/09)
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- An amphiphilic C60 derivative with a tris(2,2′-bipyridine) ruthenium(II) polar head group: Synthesis and incorporation in Langmuir films
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An amphiphilic C60 derivative with a tris(2,2′-bipyridine) ruthenium(II) polar head group has been prepared. The Langmuir film of this compound has been characterized by its surface pressure versus molecular area (Π/A) isotherm and Brewster angle microscopy (BAM) observations.
- Cardinali, Fran?ois,Gallani, Jean-Louis,Schergna, Stefano,Maggini, Michele,Nierengarten, Jean-Fran?ois
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p. 2969 - 2972
(2007/10/03)
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- Saccharide sensing molecules having enhanced fluorescent properties
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The present invention provides formulae for fluorescent compounds that have a number of properties which make them uniquely suited for use in sensors of analytes such as saccharides. The advantageous fluorescent properties include favorable excitation wavelengths, emission wavelengths, fluorescence lifetimes, and photostability. Additional advantageous properties include enhanced aqueous solubility, as well as temperature and pH sensitivity. The compound comprises an aryl or a substituted phenyl botonic acid that acts as a substrate recognition component, a fluorescence switch component, and a fluorophore. Fluorescent compounds are described that are excited at wavelengths greater than 400 nm and emit at wavelengths greater than 450 nm, which is advantageous for optical transmission through skin. The fluorophore is typically selected from transition metal-ligand complexes and thiazine, oxazine, oxazone, or oxazine-one as well as anthracene compounds. The fluorescent compound can be immobilized in a glucose permeable biocompatible polymer matrix that is implantable below the skin.
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- Synthesis, Characterization and Photochromic Studies of Spirooxazine-Containing 2,2′-Bipyridine Ligands and Their Rhenium(I) Tricarbonyl Complexes
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A series of spirooxazine-containing 2,2′-bipyridine ligands and their rhenium(I) tricarbonyl complexes has been designed and synthesized, and their photophysical, photochromic and electrochemical properties have been studied. The X-ray crystal structures
- Ko, Chi-Chiu,Wu, Li-Xin,Wong, Keith Man-Chung,Zhu, Nianyong,Yam, Vivian Wing-Wah
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p. 766 - 776
(2007/10/03)
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- Saccharide sensing molecules having enhanced fluorescent properties
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The present invention provides formulae for fluorescent compounds that have a number of properties which make them uniquely suited for use in sensors of analytes such as saccharides. The advantageous fluorescent properties include favorable excitation wav
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- Synthesis and study of the absorption and luminescence properties of polymers containing Ru(BpyMe2)32+ chromophores and coumarin laser dyes
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Polymers containing coumarin and Ru(BpyMe2)32+ chromophores were synthesized using a grafting approach and also a copolymerization approach. It was found that the solubility of polymers made from Ru-containing monomers was
- Serin, Jason,Schultze, Xavier,Adronov, Alex,Frechet, Jean M.J.
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p. 5396 - 5404
(2007/10/03)
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- Covalently linked ruthenium(II)-manganese(II) complexes: Distance dependence of quenching and electron transfer
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Continuing our development of artificial models for photosystem II in green plants, a series of compounds have been prepared in which a Ru(bpy)32+ photosensitizer is covalently linked to a manganese(II) electron donor. In addition to a trispicolylamine ligand, two other manganese ligands, dipicolylamine and aminodiacetic acid, have been introduced in order to study ligands that are appropriate for the construction of manganese dimers with open coordination sites for the binding of water. Coordination equilibria of the manganese ions were monitored by EPR. The interactions between the ruthenium and manganese moieties were probed by flash photolysis, cyclic voltammetry and steady-state and time-resolved emission measurements. The quenching of the RuII excited state by MnII was found to be rapid in complexes with short Ru-Mn distances. Nevertheless, each RuII species could be photo-oxidized by bimolecular quenching with methylviologen, and the subsequent electron transfer from MnII to RuIII could be monitored.
- Berg, Katja E.,Tran, Anh,Raymond, Mary Katherine,Abrahamsson, Malin,Wolny, Juliusz,Redon, Sophie,Andersson, Mikael,Sun, Licheng,Styring, Stenbj?rn,Hammarstr?m, Leif,Toftlund, Hans,?kermark, Bj?rn
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p. 1019 - 1029
(2007/10/03)
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- Synthesis of aryl-terminated polyenaldehydes and polyenetriethoxysilanes for preparation of self-assembled monolayers on silicon surfaces
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The synthesis of αω-terminally functionalized polyenes with arenes or hetarenes at one end and either an aldehyde or a triethoxysilyl function at the other end, capable of reacting with H-terminated or oxidized silicon surfaces, is described. Analogous to known Wittig reactions, polyenedialdehydes 1 and 3, the latter derived from 1 and phosphonium chloride 2 in a twofold Wittig olefination, were converted with phosphonium bromides 4 to give the (all-E)-arylpolyenaldehydes 5 and 6. A terminal alkyl chain was introduced in dialdehydes 1a and 3a by reaction with P,P-didecyldibenzophospholium bromide 8, resulting in polyenals 9. Wittig olefination of 5c and 9a with phosphonium chloride 2 afforded the (2-thienyl)tridecahexaenal 7 and the docosahexaenal 10. With respect to monolayer formation on oxidized Si(100) surfaces, (9-anthryl)- and (2-thienyl)-ω-functionalized polyenetriethoxysilanes 16 and 17 were prepared in a reaction sequence involving the introduction of a terminal triple bond with [3-(trimethylsilyl)prop-2-ynyl]triphenylphosphonium bromide (11), desilylation of the resulting arylpolyeninetrimethylsilanes 12, 13 with Bu4NF·3H2O, and subsequent hydrosilylation of the arylpolyenines 14, 15 using triethoxysilane under dichlorocyclooctadienylplatinum(II) catalysis.
- Effenberger,Wezstein
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p. 1368 - 1376
(2007/10/03)
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- Intramolecular Energy Transfer in Covalently Linked Polypyridine Ruthenium(II)/Osmium(II) Binuclear Complexes. Ru(II)(bpy)2Mebpy(CH2)n-MebpyOs(II)(bpy)2 (n=2, 3, 5, and 7)
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A novel series of polymethylene-linked heterobinuclear complexes of polypyridine ruthenium(II)/osmium(II) complex Ru(II)(bpy)2Mebpy-(CH2)n-MebpyOs(II)(bpy)2(bpy=2,2'-bipyridine and N=2, 3, 5, and 7), 1, was prepared.The photophysical behavior was examined in various solvents.The emission spectra of 1 (excitation wavelength: 455 nm) showed a nearly complete quenching of Ru(II) -> ?*(bpy) metal-to-ligand charge transfer (MLCT) emission and the enhancement of Os(II) -> ?*(bpy) MLCT emission.The luminescence lifetime measurements by a time-correlated single photon-counting method provided evidence that intramolecular energy transfer is a significant pathway for the observed emission quenching.The rate constants of the intramolecular energy transfer in ethanol are 5.3 * 108, 3.3 * 108, 1.3 * 108, and 1.0 * 108 s-1 for 1 (n=2, 3, 5, and 7), respectively.They were found to be proportional to the inverse sixth power on the center-to-center distance of the two complexes.The mechanisms is discussed in terms of the Foerster (a dipole-dipole interaction) mechanism.
- Furue, Masaoki,Yoshidzumi, Toshiyuki,Kinoshita, Shuichi,Kushida, Takashi,Nozakura, Shun-ichi,Kamachi, Mikiharu
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p. 1632 - 1640
(2007/10/02)
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- Molecular Basis for Bleomycin Amplification: Conformational and Stereoelectronic Effects in Unfused Amplifiers
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Sixteen unfused heterobiaromatic and diphenyl compounds substituted with an amino side chain (protonated in water) have been tested for (i) binding with DNA and (ii) their effect on the digestion of the DNA double helix by a bleomycin-iron complex.Only the DNA intercalating molecules amplify the digestion of DNA.One 2,2'-bipyridine derivative tested is an inhibitor of the bleomycin reaction because it removes ferrous ion from the bleomycin complex.Polarity of the intercalating unfused biaromatic system is of primary importance for effective binding of the molecule with native DNA and, at the same time, for its amplification activity.The molecules that have the biaromatic system polarized extensively in the direction of the side cationic chain, so that the intercalating sites constitutes a positive part of the dipole, slow strong binding with DNA and good amplification activity.For strong intercalative forces that determine the amplification activity, it is important that both the heteroaromatic subsystems of the molecule have positive ends of their dipoles positioned away from the side chain.This work provides general guidelines for synthesis of new hifhly effective bleomycin amplifiers.
- Strekowski, Lucjan,Mokrosz, Jerzy L.,Tanious, Farial A.,Watson, Rebecca A.,Harden, Donald,et al.
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p. 1231 - 1240
(2007/10/02)
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- Synthesis and Luminescence Properties of Di- and Tri-methylene Linked Tris(2,2'-bipyridine)ruthenium(II) Complex Dimers. Ground-Excited State Interaction
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Di- and tri-methylene-linked Ru(bpy)3(2+) complexes 2 were synthesized.The luminescence properties of 2 were compared with those of its component monomer.In the excited 2 systems, the intermolecular interaction leading to the enhanced quenching or the formation of a new triplet excimer was not observed.
- Furue, Masaoki,Kuroda, Noritaka,Nozakura, Shun-ichi
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p. 1209 - 1212
(2007/10/02)
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- Vinyl-substituted 2,2'-bipyridine compounds
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Vinyl-substituted 2,2'-bipyridine compounds of the formula STR1 and complexes thereof with metals or metal compounds other than alkali metals or alkaline earth metals, or alkali metal compounds, or alkaline earth metal compounds are described, R1 and R2 being as defined in patent claim 1 and the vinyl group being bonded in the 4-position or 6-position. The 2,2'-bipyridine compounds (I) are suitable for the preparation of complex-forming or complexed, crosslinked or uncrosslinked polymers. Complexed polymers, obtainable from these, are used, for example, as catalysts, in particular for transvinylation reactions. Uncomplexed polymers, which can be prepared from compounds (I), are suitable as metal ion scavengers in various applications.
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