Donor Complexes Research Articles

Exploring the Reactivity of Germole Dianions with Aluminum Trichloride: Uncovering Versatile Pathways

The reactivity analysis of dipotassiumgermoldiides K2[1] with aluminum trichloride in the presence of donors uncovers an unexpectedly broad range of products. The specific product formed varies, based on the donor's characteristics, its size, and the stoichiometric ratio between the donor and the aluminium trichloride. This leads to the formation of various products, including alumole complexes of germanium 3(Do) (with Do = OEt2, iPr2Me2Im), cationic germole complexes of aluminylenes [14]+, and 2H‐germole derivatives such as 15a. The alumole complexes of germanium 3 are structurally best described as nido‐type clusters or aluminagerma[5]pyramidanes. They show significant Lewis acidity and can be isolated only in the form of their donor complexes 3(Do). The 2H‐germole derivative 15a promises a high synthetic potential due to its unprecedented germenide (R2C = Ge(:)‐R) group group, which is part of a butadiene system and substituted with a reactive C–Al functionality.

Combined liver with other solid organ transplants: Promises, pitfalls and ethical dilemmas, an expert opinion.

Combined liver with other solid organ transplants: Promises, pitfalls and ethical dilemmas, an expert opinion.

Thermodynamic properties of a Gaussian quantum ring in the presence of a molecular ion

In this study, the findings of research conducted into the thermodynamic properties of a molecular complex ion in a 2D quantum ring characterized by Gaussian-type potentials are presented. The Schrödinger equation for a singly ionized double donor complex was solved by a two-dimensional diagonalization method. The results obtained show that at the internuclear distance, where there is coupling between the Coulomb centers such that the electron is shared by both impurity atoms, the mean energy and entropy of the system are minimal. A further finding is that in the regime where the distance between impurity atoms is comparable to the inner radius of the quantum ring, the heat capacity of the system undergoes significant changes with temperature.

High-temperature annealing induced electrical compensation in UID and Sn doped β-Ga2O3 bulk samples: The role of VGa–Sn complexes

By electron paramagnetic resonance (EPR) and photoluminescence spectroscopy, we have investigated the effect of high-temperature annealing under oxygen atmosphere on the electrical and defect properties of unintentionally doped (UID) and highly doped (Sn) n-type bulk samples of β-Ga2O3. The EPR analysis of the shallow donor concentration shows efficient electrical compensation in the Sn doped β-Ga2O3 samples but only marginal changes for the UID samples. In the Sn doped samples, we observe the formation of a Ga vacancy related acceptor defect responsible for the compensation. Its spin Hamiltonian parameters are electron spin S = 1/2, g-tensor g11 = 2.0423, g22 = 2.0160, g33 = 2.0024, and hyperfine interaction (hf) with two equivalent Ga atoms with A(69Ga) = 28 G. To identify its microscopic structure, we have performed first-principles calculations of the EPR parameters and the associated photoluminescence spectra of different Ga vacancy–Sn donor complexes, including a simple nearest neighbor pair VGa–SnGa. From these calculations, we attribute this VGa defect to a negatively charged split vacancy complex VGa1–Snib–VGa1. This VGa defect is different from the irradiation induced VGa center.

Rapid Preparation of Collagen/Red Blood Cell Membrane Tubes for Stenosis-Free Vascular Regeneration.

Extracellular matrix (ECM)-based small-diameter vascular grafts (SDVGs, inner diameter (ID) < 6 mm) hold great promise for clinical applications. However, existing ECM-based SDVGs suffer from limited donor availability, complex purification, high cost, and insufficient mechanical properties. SDVGs with ECM-like structure and function, and good mechanical properties were rapidly prepared by optimizing common materials and preparation, which can improve their clinical prospects. Here, we rapidly prepared an electrospinning film-collagen/red blood cell membrane-genipin hydrogel tube (ES-C/Rm-G-ht, ID = 2 mm) by the combination of the cross-linking of genipin, plastic compression, electrospinning, and rolling without a biological adhesive, which had a shorter preparation time of less than 17 h compared to the existing ECM-based SDVGs (preparation time of 4-18 weeks). ES-C/Rm-G-ht exhibited a layered honeycomb-like structure and demonstrated the ECM-like functions to promote the proliferation and migration of endothelial cells, and prevent thrombus and inflammation. Furthermore, ES-C/Rm-G-ht, possessing sufficient mechanical strength, showed high patency, rapid endothelialization (95%), good regeneration of smooth muscle cell layers and ECM, and effective antistenosis capability after implantation in the rabbit's carotid artery for 31 days. This work provides a straightforward, cost-effective, and promising strategy to prepare SDVGs with ECM-like structure and function, which is an ideal alternative for vascular grafts and autologous vessels in the current clinic.

Transition metal/photocatalyst-free synthesis of geminal diamines via a sandwich-like photoactive donor–acceptor–donor complex

A transition metal/photocatalyst-free access to geminal diamines is realized conveniently through an unusual sandwich-like ternary donor–acceptor–donor complex resulting from π–π stacking and base action.

A theoretical study on symmetrical non-fullerene electron acceptors molecules on BDTPT based derivatives to enhance photovoltaic properties of organic solar cells

A theoretical study on symmetrical non-fullerene electron acceptors molecules on BDTPT based derivatives to enhance photovoltaic properties of organic solar cells

The Initiation Mechanism of the Isoolefin Oligomerization Reaction in the Presence of Ethylaluminum Dichloride – Protonodonor Complex Catalysts

The mechanism of isoolefins initiation in the presence of ethylaluminum dichloride – proton donor (water, phenol, hydrochloric acid) complex catalysts has been studied by ab initio HF.3.21G. The energetics of these reactions was estimated, the values of its activation energy and thermal effects were obtained. It was found that among the studied catalysts, an increase in the activation energy of the reaction of initiation of oligomerization of isoolefins contributes to an increase in the selectivity of the process.

Potential of an Amphiphilic Artificial Corneal Endothelial Layer as a Replacement Option for Damaged Corneal Endothelium.

Bullous keratopathy, a condition severely impacting vision and potentially leading to corneal blindness, necessitates corneal transplantation. However, the shortage of donor corneas and complex surgical procedures drive the exploration of tissue-engineered corneal endothelial layers. This study develops a transparent, amphiphilic, and cell-free membrane for corneal endothelial replacement. The membrane, securely attached to the posterior surface of the cornea, is created by mixing hydroxyethyl methacrylate (HEMA) and ethylene glycol dimethylacrylate (EGDMA) in a 10:1 ratio. A 50µL volume is used to obtain a 60µm hydrophobic membrane on both sides, with one side treated with a polyvinylpyrrolidone (PVP) solution. The resulting membrane is transparent, foldable, biocompatible, amphiphilic, and easily handled. When exposed to 20% sulfur hexafluoride (SF6), the hydrophilic side of the membrane adheres tightly to the corneal Descemet's membrane, preventing water absorption into the corneal stroma, and thus treating bullous keratopathy. Histological test confirms its effectiveness, showing normal corneal structure and low inflammation when implanted in rabbits for up to 100 d. This study showcases the potential of this membrane as a viable option for corneal endothelial replacement, offering a novel approach to address donor tissue scarcity in corneal transplantation.

Implications of MHC-restricted immunopeptidome in transplantation.

The peptide presentation by donor and recipient major histocompatibility complex (MHC) molecules is the major driver of T-cell responses in transplantation. In this review, we address an emerging area of interest, the application of immunopeptidome in transplantation, and describe the potential opportunities that exist to use peptides for targeting alloreactive T cells. The immunopeptidome, the set of peptides presented on an individual's MHC, plays a key role in immune surveillance. In transplantation, the immunopeptidome is heavily influenced by MHC-derived peptides, delineating a key subset of the diverse peptide repertoire implicated in alloreactivity. A better understanding of the immunopeptidome in transplantation has the potential to open up new approaches to identify, characterize, longitudinally quantify, and therapeutically target donor-specific T cells and ultimately support more personalized immunotherapies to prevent rejection and promote allograft tolerance.

Surgical Management of Ischemic Cardiomyopathy Patients with Severe Left Ventricular Dysfunction: Is It Time to Reconsider Revascularization Surgery?

Ischemic cardiomyopathy patients with severe left ventricular dysfunction are a specific group of patients with poor surgical outcomes. There are few surgical treatment options in practice for the treatment of these patients such as heart transplantation, coronary artery bypass surgery, surgical ventricular restoration, etc. Despite multiple treatment options, there are no explicit clinical guidelines available to guide surgeons in choosing the most appropriate option and ensuring that the specific patient can benefit from the selected surgical treatment. Heart transplantation is the gold standard treatment for ischemic cardiomyopathy patients with severe left ventricular dysfunction, but it is limited to very few highly equipped centers around the world due to donor shortages, complex perioperative and surgical management, and limited technological and human resources. It is evident from some studies that heart transplant-eligible candidates can benefit from alternative surgical options such as coronary artery bypass surgery alone or combined with surgical ventricular restoration. Therefore, alternative surgical options that are used for most of the population, especially in developing and underdeveloped countries, need to be discussed to improve their outcomes. A challenge in the recent era which has yet to find a solution is to determine which heart transplant candidate can benefit from simple revascularization compared to a complex heart transplantation procedure. Myocardial viability testing was one of the most important determinants in deciding whether a patient should undergo revascularization, but its role in guiding appropriate surgical options has been challenged. This review aims to discuss the available surgical management options and their long-term outcomes for patients with ischemic cardiomyopathy, which will eventually help surgeons when choosing a surgical procedure.

Nitrogen vacancy–acceptor complexes in gallium nitride

We used photoluminescence (PL) spectroscopy and first-principles calculations to investigate GaN doped with Mg, Be, and implanted with Ca. The PL spectra revealed distinct red emission bands (RLA, where A = Be, Mg, and Ca) with maxima between 1.68 and 1.82 eV, each associated with a specific impurity. These bands consistently appeared alongside the green GL2 PL band at 2.33 eV, attributed to nitrogen vacancy (VN). Our calculations suggest that these bands result from recombination via defect complexes of group-II acceptors substituting for Ga with VN (AGaVN, A = Be, Mg, and Ca). The experimental +/0 transition levels for these complexes were estimated to be 0.6, 0.8, and 1.0 eV above the valence band maximum for Mg-, Be-, and Ca-containing complexes, respectively. The radiative recombination is facilitated by excited donor states located close to the conduction band minimum. Furthermore, our theory predicts that ZnGaVN and CdGaVN are stable and possess similar properties, although, no PL was detected from these defect complexes. The presented findings shed light on the identity of compensating donor complexes that impede the efficiency of p-type doping in GaN.

Excitation energy transfer in proteoliposomes reconstituted with LH2 and RC-LH1 complexes from Rhodobacter sphaeroides

Light-harvesting 2 (LH2) and reaction-centre light-harvesting 1 (RC-LH1) complexes purified from the photosynthetic bacterium Rhodobacter (Rba.) sphaeroides were reconstituted into proteoliposomes either separately, or together at three different LH2:RC-LH1 ratios, for excitation energy transfer studies. Atomic force microscopy (AFM) was used to investigate the distribution and association of the complexes within the proteoliposome membranes. Absorption and fluorescence emission spectra were similar for LH2 complexes in detergent and liposomes, indicating that reconstitution retains the structural and optical properties of the LH2 complexes. Analysis of fluorescence emission shows that when LH2 forms an extensive series of contacts with other such complexes, fluorescence is quenched by 52.6 ± 1.4%. In mixed proteoliposomes, specific excitation of carotenoids in LH2 donor complexes resulted in emission of fluorescence from acceptor RC-LH1 complexes engineered to assemble with no carotenoids. Extents of energy transfer were measured by fluorescence lifetime microscopy; the 0.72 ± 0.08 ns lifetime in LH2-only membranes decreases to 0.43 ± 0.04 ns with a ratio of 2:1 LH2 to RC-LH1, and to 0.35 ± 0.05 ns for a 1:1 ratio, corresponding to energy transfer efficiencies of 40 ± 14% and 51 ± 18%, respectively. No further improvement is seen with a 0.5:1 LH2 to RC-LH1 ratio. Thus, LH2 and RC-LH1 complexes perform their light harvesting and energy transfer roles when reconstituted into proteoliposomes, providing a way to integrate native, non-native, engineered and de novo designed light-harvesting complexes into functional photosynthetic systems.

Broad luminescence from Zn acceptors in Zn doped β-Ga2O3

Zn-related defects in β-Ga2O3 were studied using photoluminescence (PL) spectroscopy combined with hybrid functional calculations and secondary ion mass spectrometry. We have in-diffused Zn by heat treatments of β-Ga2O3 in Zn vapor to promote the formation of the ZnGaZni complex as the dominating Zn configuration. Subsequently, we did heat treatment in oxygen ambient to study the dissociation of the donor complex ZnGaZni into the ZnGa acceptor. The PL spectra revealed a broad band centered at 2.5 eV. The signature has a minor contribution to the overall emission of as-grown and Zn-annealed samples but increases dramatically upon the subsequent heat treatments. The theoretical predictions from hybrid functional calculation show emission energies of 2.1 and 2.3 eV for ZnGa10/− and ZnGa20/−, respectively, and given that the previously observed deviation between the experimental and calculated values for the self-trapped holes in β-Ga2O3 is about 0.2 eV, we conclude that the 2.5 eV emission we observe herein is due to the Zn acceptor.

Approach toward Low Energy Loss in Symmetrical Nonfullerene Acceptor Molecules Inspired by Insertion of Different π-Spacers for Developing Efficient Organic Solar Cells.

In this quantum approach, by adding bridge/π-spacer fragments between the donor and acceptor parts of a newly constructed DF-PCIC (A-D-A type) molecule, it is the aim to improve the photovoltaic characteristics of organic solar cells (OSCs). After π-spacer insertion into the reference molecule (DF-R), six new molecules (DF-M1 to DF-M6) were designed. The optoelectronic attributes of newly inspected molecules were theoretically calculated using MPW1PW91/6-31G(d,p) level of theory. All newly proposed molecules possessed a lower band gap (Eg), a higher value of absorption, lower reorganization energy, greater dipole moment, and lower energies of excitations than the DF-R molecule. The frontier molecular orbital study proclaimed that the DF-M1 molecule has the lowest band gap of 1.62 eV in comparison to the 2.41 eV value of DF-R. Absorption properties represented that DF-M1 and DF-M2 molecules show the highest absorption values of up to 1006 and 1004 nm, respectively, in the near-infrared region. Regarding the reorganization energy, DF-M2 has the lowest value of λe (0.0683896 eV) and the lowest value of λh (0.1566471 eV). DF-M2 and DF-M5 manifested greater dipole moments with the values of 5.514665 and 7.143434 D, respectively. The open circuit voltage (VOC) of all the acceptors was calculated with J61, a donor complex. DF-M4 and DF-M6 molecules showed higher values of VOC and fill factor than the DF-R molecule. Based on the given results, it was supposed that all the newly presented molecules might prove themselves to be better than the reference and thus might be of great interest to experimentalists. Thus, they are suggested to be used to develop proficient OSC devices with improved photovoltaic prospects in the near future.

Effect of Strain and Surface Proximity on the Acceptor Grouping in ZnO.

According to the present knowledge, the level of zinc oxide conductivity is determined by donor and acceptor complexes involving native defects and hydrogen. In turn, recently published low-temperature cathodoluminescence images and scanning photoelectron microscopy results on ZnO and ZnO/N films indicate grouping of acceptor and donor complexes in different crystallites, but the origin of this phenomenon remains unclear. The density functional theory calculations on undoped ZnO presented here show that strain and surface proximity noticeably influence the formation energy of acceptor complexes, and therefore, these complexes can be more easily formed in crystallites providing appropriate strain. This effect may be responsible for the clustering of acceptor centers only in certain crystallites or near the surface. Low-temperature photoluminescence spectra confirm the strong dependence of acceptor luminescence on the structure of the ZnO film.

Towards Incorporation in Larger Architectures: A Polymeric Halogen Bond‐Based Iridium Sensor

Abstract This study reports the synthesis and characterization of a "click‐able" iridium(III) complex as halogen bond‐based anion sensor. The functionalization is exemplarily demonstrated by the attachment of poly(ethylene glycol) azide via a "copper‐click"‐reaction. Subsequently, the polymeric XB donor complex is characterized in depth with 1H NMR spectroscopy, size exclusion chromatography, and MALDI‐ToF‐MS. Moreover, the anion binding capabilities are demonstrated with emission titrations revealing strong anion complexation. These findings emphasize the great potential of this approach to tune the complex's properties or include other functions such as cation complexation sites to exploit cooperative effects by using polymeric substituents on the iridium complex.

Gallium Vacancy—Shallows Donor Complexes in n-GaAs Doped with Elements of Group VI Te or S (Review)

Gallium Vacancy—Shallows Donor Complexes in n-GaAs Doped with Elements of Group VI Te or S (Review)

IS21 family transposase cleaved donor complex traps two right-handed superhelical crossings

Transposases are ubiquitous enzymes that catalyze DNA rearrangement events with broad impacts on gene expression, genome evolution, and the spread of drug-resistance in bacteria. Here, we use biochemical and structural approaches to define the molecular determinants by which IstA, a transposase present in the widespread IS21 family of mobile elements, catalyzes efficient DNA transposition. Solution studies show that IstA engages the transposon terminal sequences to form a high-molecular weight complex and promote DNA integration. A 3.4 Å resolution structure of the transposase bound to transposon ends corroborates our biochemical findings and reveals that IstA self-assembles into a highly intertwined tetramer that synapses two supercoiled terminal inverted repeats. The three-dimensional organization of the IstA•DNA cleaved donor complex reveals remarkable similarities with retroviral integrases and classic transposase systems, such as Tn7 and bacteriophage Mu, and provides insights into IS21 transposition.

Trap-limited diffusion of Zn in β−Ga2O3

Diffusion of Zn in (001)- and $(\overline{2}01)$-oriented $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ was studied using secondary-ion mass spectrometry and first-principles calculations based on hybrid and semilocal functionals. The $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$ samples were sealed in quartz ampules together with a piece of metallic Zn and heated to temperatures of 900--1100 ${}^{\ensuremath{\circ}}\mathrm{C}$ for 1 h. The Zn concentration profiles as a function of depth were simulated by employing the trap-limited diffusion model. From this model the migration barrier for Zn diffusion was found to be ${E}_{m}=2.2\ifmmode\pm\else\textpm\fi{}0.2\phantom{\rule{4.pt}{0ex}}$ and $2.1\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{4.pt}{0ex}}\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$ in the (001) and ($\overline{2}01$) orientations of $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Ga}}_{2}{\mathrm{O}}_{3}$, respectively, with corresponding dissociation energies of ${E}_{d}$ = 3.5 $\ifmmode\pm\else\textpm\fi{}1.1$ and $3.2\ifmmode\pm\else\textpm\fi{}0.6\phantom{\rule{4.pt}{0ex}}\phantom{\rule{0.28em}{0ex}}\mathrm{eV}$. Results from the first-principles calculations predict an interstitialcy mechanism for the Zn diffusion when it is not in its trapped state. Using the nudged elastic band method, we obtain a barrier of 1.6 eV for migration of Zn split interstitials $({\mathrm{Zn}}_{i})$ in both the [001] and $[\overline{2}01]$ directions, in accordance with the results obtained from the trap-limited diffusion model. Interestingly, the Ga vacancy is found to be able to trap two Zn atoms forming a shallow donor complex labeled ${\mathrm{Zn}}_{i}{\mathrm{Zn}}_{\mathrm{Ga}}$. The energy needed for ${\mathrm{Zn}}_{i}$ to dissociate from this donor complex is estimated to be 2.99 eV, in reasonable agreement with the trap dissociation energies extracted from the diffusion model.