Search results for "Acceptor"
showing 10 items of 394 documents
All-organic fast intersystem crossing assisted exciplexes exhibiting sub-microsecond thermally activated delayed fluorescence
2021
A novel strategy is presented towards acquisition of exciplex systems exhibiting thermally activated delayed fluorescence (TADF) with a high reverse intersystem crossing (RISC) rate (exceeding 107 s−1). This approach involves constructing exciplex donor–acceptor molecular pairs, where the acceptor molecule possesses the ability to undergo fast and efficient intersystem crossing (ISC). With the use of 6-cyano-9-phenylpurine (PCP) acceptor and carbazole-based donor molecules, exciplexes were obtained, where the excitation is contained on PCP and undergoes fast ISC to form a local excited triplet state (3LEA). The controlled excitation transfer to the 3LEA level provides an optimal reverse int…
Self-ordering of metallogrid complexes via directed hydrogen-bonding.
2012
Reaction of imidazole aldehydes with dihydrazino derivatives of 2-phenylpyrimidine provides a family of bis(acylhydrazone) ligands which form [2 × 2] metallogrid complexes with transition metal ions including Fe(II), Co(II), Cu(II) and Zn(II). The free ligands show H-bonding interactions, both donor and acceptor, largely involving the imidazole units, while binding of the metal ions occupies all the acceptor sites and leaves only the pyrrolic-NH site as an H-bond donor, although its deprotonation by a strong base can regenerate an acceptor. These H-bonding interactions have been studied by (1)H NMR spectroscopy in solution and in the solid state by means of several crystal structure determi…
Energy Transfer between Surface-Immobilized Light-Harvesting Chlorophyll a/b Complex (LHCII) Studied by Surface Plasmon Field-Enhanced Fluorescence S…
2010
The major light-harvesting chlorophyll a/b complex (LHCII) of the photosynthetic apparatus in green plants can be viewed as a protein scaffold binding and positioning a large number of pigment molecules that combines rapid and efficient excitation energy transfer with effective protection of its pigments from photobleaching. These properties make LHCII potentially interesting as a light harvester (or a model thereof) in photoelectronic applications. Most of such applications would require the LHCII to be immobilized on a solid surface. In a previous study we showed the immobilization of recombinant LHCII on functionalized gold surfaces via a 6-histidine tag (His tag) in the protein moiety. …
Tetrathiafulvalene-Based Mixed-Valence Acceptor-Donor-Acceptor Triads: A Joint Theoretical and Experimental Approach
2013
This work presents a joint theoretical and experimental characterisation of the structural and electronic properties of two tetrathiafulvalene (TTF)-based acceptor-donor-acceptor triads (BQ-TTF-BQ and BTCNQ-TTF - BTCNQ; BQ is naphthoquinone and BTCNQ is benzotetracyano-p-quinodimethane) in their neutral and reduced states. The study is performed with the use of electrochemical, electron paramagnetic resonance (EPR), and UV/Vis/NIR spectroelectrochemical techniques guided by quantum-chemical calculations. Emphasis is placed on the mixed-valence properties of both triads in their radical anion states. The electrochemical and EPR results reveal that both BQ-TTF-BQ and BTCNQ-TTF-BTCNQ triads in…
Selective recognition of neutral guests in an aqueous medium by a biomimetic calix[6]cryptamide receptor
2015
The design of artificial receptors that can efficiently work in water is a challenging research area. A possible biomimetic approach for the elaboration of such receptors consists of associating a hydrophobic cavity with a polar polyfunctional binding site. On this basis, a hydrophilic calix[6]cryptamide decorated with oligo(ethylene glycol) units (i.e. 8) was synthesized through an efficient [1 + 1] macrocyclization reaction as the key-step. The complexation of neutral molecules was evaluated by NMR spectroscopy through competition experiments either in apolar or aqueous media. In both media, host 8 can bind neutral species that display H-bonding acceptor and donor groups such as amides or…
Face-to-face held Pacman type porphyrin-fullerene dyads: design, synthesis, charge transfer interactions and photophysical studies
2008
Pacman-type face-to-face zinc-porphyrin-fullerene dyads have been newly synthesized and studied. Owing to the close proximity of the donor and acceptor entities, strong pi-pi intramolecular interactions between the porphyrin and fullerene entities resulted in modulating the spectral and electrochemical properties of the dyads. New absorption and emission bands that correspond to the charge-transfer interactions were observed in the near-IR region. Time-resolved transient absorption studies revealed efficient photoinduced electron transfer from the singlet excited porphyrin to the fullerene entity. The rate constants for photoinduced electron transfer are analyzed in terms of the Marcus theo…
Ferrocene compounds: methyl 1′-aminoferrocene-1-carboxylate
2010
The title compund, [Fe(C(5)H(6)N)(C(7)H(7)O(2))], features one strong intermolecular hydrogen bond of the type N-H...O=C [N...O = 3.028 (2) A] between the amine group and the carbonyl group of a neighbouring molecule, and vice versa, to form a centrosymmetric dimer. Furthermore, the carbonyl group acts as a double H-atom acceptor in the formation of a second, weaker, hydrogen bond of the type C-H...O=C [C...O = 3.283 (2) A] with the methyl group of the ester group of a second neighbouring molecule at (x, -y - 1/2, z - 1/2). The methyl group also acts as a weak hydrogen-bond donor, symmetry-related to the latter described C-H...O=C interaction, to a third molecule at (x, -y - 1/2, z + 1/2) t…
A Fluorine Scan at the Catalytic Center of Thrombin: CF, COH, and COMe Bioisosterism and Fluorine Effects on pKa and logD Values
2006
A series of 16 tricyclic thrombin inhibitors was prepared by using the 1,3-dipolar cycloaddition of azomethine ylides derived from 3- or 4-hydroxyproline and 4-bromobenzaldehyde, with N-(4-fluorobenzyl)maleimide as the key step. The terminal pyrrolidine ring of the inhibitors was systematically substituted to explore the potential bioisosteric behavior of C-F, C-OH, and C-OMe residues pointing into the environment of the catalytic center of a serine protease. X-ray crystal structure analyses revealed a distinct puckering preference of this ring. Substitution by F, HO, and MeO has a strong effect on the basicity of the adjacent pyrrolidine nitrogen center which originates from two sigma-indu…
Design of Triads for Probing the Direct Through Space Energy Transfers in Closely Spaced Assemblies
2013
Using a selective stepwise Suzuki cross-coupling reaction, two trimers built on three different chromophores were prepared. These trimers exhibit a D(^)A1-A2 structure where the donor D (octa-β-alkyl zinc(II)porphyrin either as diethylhexamethyl, 10a, or tetraethyltetramethyl, 10b, derivatives) through space transfers the S1 energy to two different acceptors, di(4-ethylbenzene) zinc(II)porphyrin (A1; acceptor 1) placed cofacial with D, and the corresponding free base (A2; acceptor 2), which is meso-meso-linked with A1. This structure design allows for the possibility of comparing two series of assemblies, 9a,b (D(^)A1) with 10a,b (D(^)Â1-A2), for the evaluation of the S1 energy transfer for…
Molecular dynamics of discotic charge-transfer complexes, dielectric spectroscopy and2H NMR studie
1994
Abstract Using a combination of solid state 2H NMR spectroscopy on selectively deuteriated samples and dielectric spectroscopy, the molecular dynamics of discotic charge-transfer (CT) complexes were investigated. These complexes show particular thermodynamic and flow properties. Considered were mixtures of low molar mass donors and acceptors, low molar mass donors with main chain acceptor polymers and covalently linked donor-acceptor twins with different lengths of the spacer. A main result is that correlated rotational motions of discotic molecules or groups about the columnar axis are observed in all systems except for the twin with the short spacer. This type of motion seems to be a gene…