Search results for "donor"
showing 10 items of 436 documents
Red- and Blue-Shifts in Oligo(1,4-phenyleneethynylene)s Having Terminal Donor−Acceptor Substitutions
2004
Four series of oligo(1,4-phenyleneethynylene)s (OPEs), 1−4 (a−d), each having a terminal dialkylamino group as their electron donor, were prepared by applying Sonogashira−Hagihara reactions and a protecting group strategy. To study the influence that the push−pull effect has on the long-wavelength absorption, three of the four series of OPEs contain terminal acceptor groups (CN, CHO, NO2). Extending the conjugation (increasing the number of repeat units, n) lowers the energy E(n) of the electron transition in the purely donor-substituted series 1a−4a (bathochromic shift). This effect is superimposed in the push−pull series 1−4 (b−d) by the effect of the intramolecular charge transfer (ICT),…
G2(MP2) study of the substituent effects in the H3BXHnMe3−n (X=N, P; n=0–3) donor–acceptor complexes
1998
Abstract The complexation energies of H 3 BXH n Me 3− n (X=N, P; n =0–3) donor–acceptor complexes have been investigated at the G2(MP2) level of theory. MP2(Full)/6-31G(d) optimized geometries and G2(MP2) calculated complexation energies are in good agreement with experiment. Increasing methyl substitutions on `X' donor atom augments both the basicity of XH n Me 3− n Lewis bases and the stability of complex. The NBO partitioning scheme suggests that there is no correlation between the charge transfer and the complexation energies.
Selenophene-Based Hole-Transporting Materials for Perovskite Solar Cells
2021
Two novel and simple donor-π-bridge-donor (D-π-D) hole-transporting materials (HTMs) containing two units of the p-methoxytriphenylamine (TPA) electron donor group covalently bridged by means of the 3,4-dimethoxyselenophene spacer through single and triple bonds are reported. The optoelectronic and thermal properties of the new selenium-containing HTMs have been determined using standard experimental techniques and theoretical density functional theory (DFT) calculations. The selenium-based HTMs have been incorporated in mesoporous perovskite solar cells (PSCs) in combination with the triple-cation perovskite [(FAPbI3 )0.87 (MAPbBr3 )0.13 ]0.92 [CsPbI3 ]0.08 . Limited values of power conver…
Photoinduced Single Electron Transfer on 5-Aryl-1,2,4-oxadiazoles: Some Mechanistic Investigations in the Synthesis of Quinazolin-4-ones
1999
The photochemistry of some 5-aryl-3-methoxy- (or 5-aryl-3-phenyl-) 1,2,4-oxadiazoles irradiated in the presence of different sensitizers [such as diphenylacetylene (DAC), 9,10-diphenylanthracene (DAN), or triphenylene (TPH)] or ground-state donors such as triethylamine (TEA) has been investigated. Intermediates arising from breaking of the ring O-N bond develop both into quinazolin-4-ones (by a heterocyclization reaction involving the aryl at the C-5 of the oxadiazole nucleus) and into open-chain products (corresponding to a reduction at the ring O-N bond), in different ratios depending on their structures and photoreaction conditions. A reasonable explanation considers sensitization by pho…
ChemInform Abstract: Photoinduced Single Electron Transfer on 5-Aryl-1,2,4-oxadiazoles: Some Mechanistic Investigations in the Synthesis of Quinazoli…
2010
The photochemistry of some 5-aryl-3-methoxy- (or 5-aryl-3-phenyl-) 1,2,4-oxadiazoles irradiated in the presence of different sensitizers [such as diphenylacetylene (DAC), 9,10-diphenylanthracene (DAN), or triphenylene (TPH)] or ground-state donors such as triethylamine (TEA) has been investigated. Intermediates arising from breaking of the ring O-N bond develop both into quinazolin-4-ones (by a heterocyclization reaction involving the aryl at the C-5 of the oxadiazole nucleus) and into open-chain products (corresponding to a reduction at the ring O-N bond), in different ratios depending on their structures and photoreaction conditions. A reasonable explanation considers sensitization by pho…
Controlling Spin-Correlated Radical Pairs with Donor-Acceptor Dyads: A New Concept to Generate Reduced Metal Complexes for More Efficient Photocataly…
2021
Abstract One‐electron reduced metal complexes derived from photoactive ruthenium or iridium complexes are important intermediates for substrate activation steps in photoredox catalysis and for the photocatalytic generation of solar fuels. However, owing to the heavy atom effect, direct photochemical pathways to these key intermediates suffer from intrinsic efficiency problems resulting from rapid geminate recombination of radical pairs within the so‐called solvent cage. In this study, we prepared and investigated molecular dyads capable of producing reduced metal complexes via an indirect pathway relying on a sequence of energy and electron transfer processes between a Ru complex and a cova…
Orgānu un audu izņemšana no cilvēka - cilvēktiesību pārkāpums?
2017
Darbā “Orgānu un audu izņemšana no cilvēka – cilvēktiesību pārkāpums?” tiek izpētīta likumīga cilvēka orgānu un audu transplantācija, kā arī nelikumīga orgānu un audu izņemšana, kas ir neatļauta un noziedzīga darbība. Orgānu un audu izņemšanas cilvēktiesību jautājums saasinājās pēdējo 40 gadu laikā, sakarā ar zinātnes attīstību transplantācijas jomā un cilvēktiesību lomas pieaugumu medicīnas un pacientu tiesībās. Tāpēc bakalaura darbā autore apskata orgānu un audu izņemšanas juridiskās īpatnības un tas rezultātā radītos cilvēktiesību aizskārumus. Orgānu un audu izņemšanas problēma mūsdienās ir ļoti svarīga un izplatīta, jo orgānu un audu pieprasījums ir lielāks nekā orgānu piedāvājums, tāpē…
Synthesis, characterization and magnetic study of two new octahedral iron(III) complexes with pendant zwitterionic Schiff bases
2016
Two Schiff bases, HL1 [2-((3-(dimethylamino)propylimino)methyl)-5-bromophenol] and HL2 [2-((2-(diethylamino)ethylimino)methyl)-6-methoxyphenol], have been employed to prepare two new octahedral iron(III) complexes, [Fe(HL1)2(N3)2]ClO4·2H2O (1) and [Fe(HL2)2(NCS)2]ClO4·H2O (2). Both complexes are characterized by spectral and elemental analyses. Single crystal X-ray diffraction studies confirm their structures. In both complexes, Schiff bases are trapped in their zwitterionic forms and coordinated to iron(III) only through the imine nitrogen and phenoxo oxygen, i.e., they behave as bi-dentate ligands, keeping the remaining potential donor sites pendant. The measurement of χM vs. T for both c…
Zvaguļu Rhinanthus spp. un nārbuļu Melampyrum spp. potenciāls dabisko zālāju atjaunošanā LIFE programmas projekta GrassLIFE saimniecībās
2020
Bakalaura darba mērķis ir noskaidrot zvaguļu un nārbuļu resursus LIFE programmas projekta GrassLIFE saimniecību apkārtnē un izvērtēt to potenciālu dabisko zālāju biotopu atjaunošanā. Darbā sniegts ieskats par dabiskiem zālājiem un to aizsardzību, kā arī par metodēm zālāju atjaunošanai. Darbā apskatīta zvaguļa ģints un nārbuļa ģints sugu ekoloģija, bioloģija un morfoloģija, un to izmantošanas iespējas un metodika pļavas atjaunošanai. Izmantojot Dabas aizsardzības pārvaldes datus par abu ģinšu sugu atradnēm dabiskajos zālājos, noskaidrota Rhinanthus spp. un Melampyrum spp. izplatība Latvijas dabiskajos zālājos, un izveidotas abu ģinšu sugu, kas sastopamas dabiskajos zālājos, izplatības un sas…
Przeszczepy narządowe w okresie epidemii COVID-19
2020
Epidemia COVID-19 zmieniła podejście do kwalifikacji dawców i biorców przeszczepów narządowych. Kwalifikacja następuje po obowiązkowym wykonaniu tomografii komputerowej płuc i testu RT-PCR na obecność wirusa, w wyniku indywidualnej oceny korzyści i ryzyka zakażenia. W bardziej odległym okresie od transplantacji na ciężkość objawów w większym stopniu niż leczenie immunosupresyjne wpływają zaawansowany wiek i współchorobowości. Pierwszym krokiem w redukcji leczenia immunosupresyjnego u biorców przeszczepów narządowych jest odstawienie leku antyproliferacyjnego z pozostawieniem inhibitora kalcyneuryny i steroidów. Terapia immunosupresyjna znamiennie wydłuża czas eliminacji wirusa, ale może ogr…