Search results for "Conjugated"
showing 10 items of 288 documents
3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazine - Synthese, Fl�ssigkristallinit�t und Photochemie
1995
3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazines - Synthesis, LC Properties and Photochemistry The (E,E)-3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazines 8 were prepared in a synthetic sequence starting with aromatic aldehydes 1 and cinnamic acids 2, respectively (Scheme 1). The rod-like conjugated molecules represent calamitic mesogens as well as extended chromophores. Hence, we investigated the formation of liquid crystals, achieved by the introduction of long flexible side chains, and the photochemical behaviour that is characterized by the fragmentation of the central ring (Scheme 3).
Of Thiols and Disulfides: Methods for Chemoselective Formation of Asymmetric Disulfides in Synthetic Peptides and Polymers.
2018
In protein or peptide chemistry, thiols are frequently chosen as a chemical entity for chemoselective modification reactions. Although it is a well-established methodology to address cysteines and homocysteines in aqueous media to form S-C bonds, possibilities for the chemoselective formation of asymmetric disulfides have been less approached. Focusing on bioreversibility in conjugation chemistry, the formation of disulfide bonds is highly desirable for the attachment of thiol-containing bioactive agents to proteins or in cross-linking reactions, because disulfide bonds can combine stability in blood with degradability inside cells. In this Concept article, recent approaches in the field of…
Conjugated Porphyrin Dimers: Cooperative Effects and Electronic Communication in Supramolecular Ensembles with C60
2016
International audience; Two new conjugated porphyrin-based systems (dimers 3 and 4) endowed with suitable crown ethers have been synthesized as receptors for a fullerene-ammonium salt derivative (1). Association constants in solution have been determined by UV–vis titration experiments in CH2Cl2 at room temperature. The designed hosts are able to associate up to two fullerene-based guest molecules and present association constants as high as ∼5 × 108 M–1. Calculation of the allosteric cooperative factor α for supramolecular complexes [3·12] and [4·12] showed a negative cooperative effect in both cases. The interactions accounting for the formation of the associates are based, first, on the …
Carbon Nanotubes Conjugated with Triazole-Based Tetrathiafulvalene-Type Receptors for C60 Recognition
2019
Fullerene receptors prepared by a twofold CuI -catalyzed azide-alkyne cycloaddition (CuAAC) reaction with -extended tetrathiafulvalene (exTTF) have been covalently linked to singlewalled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The nanoconjugates obtained were characterized by several analytical, spectroscopic and microscopic techniques (TEM, FTIR, Raman, TGA and XPS), and evaluated as C60 receptors by UV-Vis spectroscopy. The complexation between the exTTF-triazole receptor in the free state and C60 was also studied by UV-Vis and 1 H NMR titrations, and compared with analogous triazole-based tweezer-type receptors containing the electron-acceptor 11,11,12,12-t…
Can aromaticity be connected with molecular polarizability? A theoretical study of benzene isomers and five-membered heterocyclic molecules
2004
Extended calculations of molecular electric dipole polarizability tensor, at Hartree-Fock and correlated level of accuracy (MP2, CCS, CC2, CCSD, and CCSD(T)) have been carried out to investigate whether aromaticity could be related to the electric dipole polarizability of planar ring systems. The calculations prove the exaltation of the average property of conjugated molecules, which is possibly due to their easily polarizable π-electron cloud. On the other hand, theoretical out-of-plane polarizability components are smaller in benzene than in any other C$_6$H$_6$ isomer. The aromatic stabilization energies of monosubstituted five-membered conjugated cyclic molecules increase in the same di…
Direct chemical grafted curcumin on halloysite nanotubes as dual-responsive prodrug for pharmacological applications
2016
Covalently functionalized halloysite nanotubes (HNTs) were successfully employed as dual-responsive nanocarriers for curcumin (Cur). Particularly, we synthesized HNT-Cur prodrug with a controlled curcumin release on dependence of both intracellular glutathione (GSH) and pH conditions. In order to obtain HNT-Cur produgs, halloysite was firstly functionalized with cysteamine through disulphide linkage. Afterwards, curcumin molecules were chemically conjugated to the amino end groups of halloysite via Schiff's base formation. The successful functionalization of halloysite was proved by thermogravimetric analysis, FT-IR spectroscopy, dynamic light scattering and scanning electron microscopy. Ex…
1,4-Dihydro-1-methyl-4-nitriminopyridine Dihydrate
1998
Molecules of the title compound, C6H7N302.2H20, are almost planar with the NNO2 nitrimino group twisted 8 (1) ° out of the plane of the pyridine ring. The nitrimino group and CsN ring form a conju- gated 7r-electron system. These molecules together with water molecules are arranged in planes, They are con- nected with each other by O--H.-.O, O--H...N and weaker C--H..-O hydrogen bonds. Four water mol- ecules form a planar square (OH..-O--H)2 ring with O-..O distances equal to 2.741 (2) and 2.778(2)A. These rings join pairs of molecular planes into double layers, interacting otherwise by van der Waals forces.
Harnessing medically relevant metals onto water-soluble subphthalocyanines: towards bimodal imaging and theranostics
2014
International audience; Subphthalocyanine (SubPc), a putative fluorophore for optical imaging (OI), was conjugated to chelating ligands (DOTA, DTPA) affording water-soluble conjugates complexed with (non-radioactive) metals relevant to the following medical imaging techniques/therapies: MRI (Gd), PET (Cu, Ga), SPECT (In, Ga, Lu), RIT (Cu, Lu, Y), and NCT (Gd). Magneto-optical properties of ditopic gadolinium species (and optical properties of other metal containing species) were examined (brightness (ε × Φ F) and relaxivity R 1) and fluorescence confocal/biphoton microscopy studies were conducted. † Electronic supplementary information (ESI) available: Experimental characterization, NMR and…
Effect of free rotation in polypyridinic ligands of Ru(ii) complexes applied in light-emitting electrochemical cells
2013
In the present work we report the synthesis and the electrochemical, photoluminescent and electroluminescent properties of two new Ru(II) complexes described by the general formula [Ru(phen)2X](2+), where phen is 1,10-phenanthroline. The X ligand consists of a 2,2'-bipyridine (bpy) unit substituted with two phenyl rings connected to the bpy core through a saturated (Lhydro = 4,4'-diphenylethyl-2,2'-bipyridine) or a conjugated (LH = 4,4'-bis(α-styrene)-2,2'-bipyridine) carbon-carbon bridge. The photoluminescent spectra indicate that, both in solution and solid state, the complex bearing the aliphatic substitution bridges exhibits a higher quantum yield and a longer excited state lifetime tha…
Physicochemical Characterization of σ-Bonded Aryl Iron(III) Porphycenes. X-ray Structures of (EtioPc)Fe(3,5-C6F2H3) and (EtioPc)In(C6H5), Where EtioP…
1998
A series of iron(III) σ-bonded porphycenes are characterized by their electrochemical and spectroscopic properties. The investigated compounds are represented as (EtioPc)Fe(R), where EtioPc = the dianion of 2,7,12,17-tetraethyl-3,6,13,16-tetramethylporphycene and R = C6H5, 3,5-C6F2H3, 3,4,5-C6F3H2 or 2,3,5,6-C6F4H. Each compound is characterized as to its ESR, NMR, and UV−visible properties which are compared to corresponding compounds in an analogous series of (OEP)Fe(R) and (OETPP)Fe(R) derivatives where OEP and OETPP are the dianions of octaethyl- and octaethyltetraphenylporphyrin, respectively. The (EtioPc)Fe(R) complexes contain either high- or low-spin Fe(III), depending on the specif…