- Spiroconjugated Donor-σ-Acceptor Charge-Transfer Dyes: Effect of the ?-Subsystems on the Optoelectronic Properties
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Charge-transfer-based materials with intramolecular donor-acceptor structures are attractive for technological applications. Herein, a series of donor-σ-acceptor dyes has been prepared in a modular approach. The design of these intramolecular charge-transfer dyes is based on the concept of spiroconjugation, which leads to unique materials with special optical properties. The optical transitions are based on intramolecular charge transfer, as shown by solvatochromic measurements and density functional theory (DFT) calculations. Crystallographic, computational, electrochemical, and optical studies were performed to clarify the effect of different perpendicular ?-moieties on the optoelectronic properties. Our molecular tuning allowed for the synthesis of molecules exhibiting strong visible-range absorption. The compounds are not fluorescent due to structural changes in the excited state, as revealed by DFT calculations. Finally, our study describes enantiomerically pure spiroconjugated absorber molecules using 1,1′-binaphthyl-2,2′-diol (BINOL) units on the donor part.
- Esser, Birgit,W?ssner, Jan S.
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p. 5048 - 5057
(2020/05/01)
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- Metal organic frameworks as heterogeneous catalysts for the selective N-methylation of aromatic primary amines with dimethyl carbonate
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Metal organic frameworks (MOFs) with aluminium, copper and iron as central metal atoms with 1,4-benzenedicarboxylic acid (aluminium) and 1,3,5-benzenetricarboxylic acid (copper and iron) as ligands are selective and active catalysts in promoting the polymethylation of aromatic amines with dimethyl carbonate (DMC). N-methylation prevails over carbamoylation even though they are competing parallel processes. The present N-methylation protocol using DMC enjoys advantages such as convenient reaction conditions, benign, reusable, cost-effective catalyst, avoids the use of additional solvent and uses a safe, green methylating agent that only produces CO2 and methanol as by-products.
- Dhakshinamoorthy, Amarajothi,Alvaro, Mercedes,Garcia, Hermenegildo
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experimental part
p. 19 - 25
(2010/08/20)
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- Shiga toxin-mediated retrograde delivery of a topoisomerase I inhibitor prodrug
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(Figure Presented) A retrograde strategy: An innovative cancer-cell delivery concept exploits the naturally evolved characteristics of the Shiga toxin B-subunit (STxB) for the intracellular activation of a newly synthesized prodrug at the level of the bio
- El Alaoui, Abdessamad,Schmidt, Frederic,Amessou, Mohamed,Sarr, Marianne,Decaudin, Didier,Florent, Jean-Claude,Johannes, Ludger
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p. 6469 - 6472
(2008/09/17)
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- CHEMICAL LINKERS AND CONJUGATES THEREOF
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The present disclosure provides drug-ligand conjugates that are potent cytotoxins, wherein the drug is linked to the ligand through either a peptidyl, hydrazine, or disulfide linker. The disclosure is also directed to compositions containing the drug-liga
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Page/Page column 151
(2008/06/13)
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- Mono-N-methylation of functionalized anilines with alkyl methyl carbonates over NaY faujasites. 4. Kinetics and selectivity
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(Chemical Equation Presented) In the presence of NaY faujasite as the catalyst, the reaction of bifunctional anilines (1-4: XC6H 4-NH2; X = OH, CO2H, CH2OH, and CONH2) with methyl alkyl carbonates [MeOCO2R′: R′ = Me or MeO(CH2)2O(CH2)2] proceeds with a very high mono-N-methyl selectivity (XC6H 4NHMe up to 99%), and chemoselectivity as well, with other nucleophilic functions (OH, CO2H, CH2OH, CONH2) fully preserved from alkylation and/or transesterification reactions. Aromatic substituents, however, modify the relative reactivity of amines 1-4: good evidence suggests that, not only steric and electronic effects, but, importantly, direct acid-base interactions between substituents and the catalyst are involved. Weakly acidic groups (OH, CH2OH, CONH2, pKa ≥ 10) may help the reaction, while aminobenzoic acids (pK a of 4-5) are the least reactive substrates. The solvent polarity also affects the reaction, which is faster in xylene than in the more polar diglyme. The mono-N-methyl selectivity is explained by the adsorption pattern of reagents within the zeolite pores: a BAl2 displacement of the amine on methyl alkyl carbonate should occur aided by the geometric features of the NaY supercavities. Different factors account for the reaction chemoselectivity. Evidence proves that the polarizability of the two nucleophilic terms (NH 2 and X groups) of anilines is relevant, although adsorption and confinement phenomena of reagents promoted by the zeolite should also be considered.
- Selva, Maurizio,Tundo, Pietro,Foccardi, Tommaso
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p. 2476 - 2485
(2007/10/03)
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- Spiroconjugated charge-transfer dyes for optical applications
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New intramolecular charge-transfer organic dyes are described. The design of these molecules is based on the phenomenon of spiroconjugation, and it provides a modular approach to the preparation of unique materials with interesting optical properties. In the dyes of the invention, the lowest unoccupied molecular orbital (LUMO) of the acceptor part (based on indandione) is spiroconjugated with the highest unoccupied molecular orbital (HOMO) of the donor part (amines, alcohols and thiols). The interaction between the donor and acceptor is controlled by the energy and symmetry of the frontier orbitals. The novel dyes described herein, with predictable and tunable optical properties, can be used in many optical applications including nonlinear optics (NLO).
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- Optical properties of spiroconjugated charge-transfer dyes
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A new type of intramolecular charge-transfer dye has been prepared. The LUMO of the acceptor part (1,3-indandione) in these compounds is spiroconjugated with the HOMO of the donor part (aromatic diamine or amino thiol). The interaction between the donor and acceptor is controlled by the energy and symmetry of the frontier orbitals. The ground state dipole moments of these compounds are aligned along the long molecular axes. In the solid state, distortions of structures are observed that are consistent with partial electron shift from the donor to the acceptor. Much more pronounced electron density shifts accompany the electronic transition that is observed in the visible region of the spectrum. These transitions are of the charge-transfer (CT) type, as shown by solvatochromic and electrooptical studies. The excited state dipole moments are in the direction opposite to that of the ground state. These observations are consistent with the excited state having radical ion pair character. The new dyes are modeled using a simple Mulliken charge-transfer theory. The mixing coefficient of neutral and ionic wave functions describing these systems is used as a measure of spiroconjugation between the subchromophores. The electrooptical data provide an estimate of the contribution of the CT transitions to the hyperpolarizabilities (β) within the two-state model. The measured values of β indicate, however, that spiro dyes have two opposing contributions to their hyperpolarizabilities, one from the CT transition and one due to the acceptor subchromophore.
- Maslak, Przemyslaw,Chopra, Anu,Moylan, Christopher R.,Wortmann, Rüdiger,Lebus, Sonja,Rheingold, Arnold L.,Yap, Glenn P. A.
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p. 1471 - 1481
(2007/10/03)
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- 1,3,2λ5-Benzothiazaphosphole 2-Oxide and 1,3,2λ5-Benzoxazaphosphole 2-Oxide Derivatives, New and Versatile Phosphorylating Reagents
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The synthesis of the highly reactive five-membered cyclic phosphorylating reagents 6a and 12 is decribed.The reagent 6a monophosphorylates alcohols without ring opening, whereas 12 diphosphorylates with ring opening yielding phosphate triesters.
- Jacob, Peter,Richter, Wolfgang,Ugi, Ivar
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p. 519 - 522
(2007/10/02)
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- THERMOLYSIS OF QUARTENARY SALTS OF 2-METHYLBENZOTHIAZOLE AND THEIR METHYLENE BASES
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The pathways of the thermal transformations of quartenary salts of 2-methylbenzothiazole and their methylene bases were investigated.The schemes of the thermal fragmentation of these compounds are discussed.The possibility of the formation of methylene bases in the thermolysis of quartenary salts of 2-methylbenzothiazole is demonstrated.
- Al'perovich, M. A.,Khesin, V. G.,Raikhina, R. D.,Medvedeva, T. D.
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p. 1182 - 1187
(2007/10/02)
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