Mixed Dimers Research Articles

Surface structure of MOVPE-prepared As-modified Si(100) substrates

In the pursuit of high-efficiency tandem devices for solar energy conversion based on III-V-semiconductors, low-defect III-V nucleation on Si(100) substrates is essential. Here, hydrogen and arsenic are key ingredients in all growth processes with respect to industrially scalable metalorganic vapor phase epitaxy. Our study provides insight into Si(100) surface preparation for the initial stage of III-V nucleation. The samples investigated, prepared on substrates with different offcut angles, show single domain surfaces consisting of rows of preferentially buckled dimers. Low energy electron diffraction and reflection anisotropy spectroscopy confirm well-defined (1 × 2)/(2 × 1) majority domains. Fourier-transform infrared spectroscopy revealed hydrogen bonding to the surface dimers, while no impurities were found by XPS. Density functional theory calculations support the experimental results and reveal a novel surface motif of H-passivated Si-As mixed dimers.

Infrared spectra of partially deuterated water dimers in the fundamental O-D stretch region.

Spectra of mixed H/D water dimers are studied in the mid-infrared region of the O-D stretch fundamental (2630-2800cm-1) using a pulsed supersonic slit jet and a tunable optical parametric oscillator infrared source. Over 30 bands, belonging to nine of the ten possible isotopologues (only H2O-HOD is missed), are observed and analyzed. The implications for excited state tunneling splittings, lifetime effects, and vibrational shifts are discussed. These are the first significant new experimental results on (gas phase) mixed water dimers in over 25 years, and they are valuable for testing water dimer theoretical calculations, a field which continues to be of lively current interest.

Supramolecular hydrogen-bonded networks formed from copper(II) carboxylate dimers.

The well-known copper carboxylate dimer, with four carboxylate ligands extending outwards towards the corners of a square, has been employed to generate a series of crystalline compounds. In particular, this work centres on the use of the 4-hydroxybenzoate anion (Hhba-) and its deprotonated phenolate form 4-oxidobenzoate (hba2-) to obtain complexes with the general formula [Cu2(Hhba)4-x(hba)xL2-y]x-, where L is an axial coligand (including solvent molecules), x = 0, 1 or 2, and y = 0 or 1. In some cases, short hydrogen bonds result in complexes which may be represented as [Cu2(Hhba)2(H0.5hba)2L2]-. The main focus of the investigation is on the formation of a variety of extended networks through hydrogen bonding and, in some crystals, coordinate bonds when bridging coligands (L) are employed. Crystals of [Cu2(Hhba)4(dioxane)2]·4(dioxane) consist of the expected Cu dimer with the Hhba- anions forming hydrogen bonds to 1,4-dioxane molecules which block network formation. In the case of crystals of composition [Et4N][Cu2(Hhba)2(H0.5hba)2(CH3OH)(H2O)]·2(dioxane), Li[Cu2(Hhba)2(H0.5hba)2(H2O)2]·3(dioxane)·4H2O and [Cu2(Hhba)2(H0.5hba)2(H0.5DABCO)2]·3CH3OH (DABCO is 1,4-diazabicyclo[2.2.2]octane), square-grid hydrogen-bonded networks are generated in which the complex serves as one type of 4-connecting node, whilst a second 4-connecting node is a hydrogen-bonding motif assembled from four phenol/phenolate groups. Another two-dimensional (2D) network based upon a related square-grid structure is formed in the case of [Et4N]2[Cu2(Hhba)2(hba)2(dioxane)2][Cu2(Hhba)4(dioxane)(H2O)]·CH3OH. In [Cu2(Hhba)4(H2O)2]·2(Et4NNO3), a square-grid structure is again apparent, but, in this case, a pair of nitrate anions, along with four phenolic groups and a pair of water molecules, combine to form a second type of 4-connecting node. When 1,8-bis(dimethylamino)naphthalene (bdn, `proton sponge') is used as a base, another square-grid network is generated, i.e. [Hbdn]2[Cu2(Hhba)2(hba)2(H2O)2]·3(dioxane)·H2O, but with only the copper dimer complex serving as a 4-connecting node. Complex three-dimensional networks are formed in [Cu2(Hhba)4(O-bipy)]·H2O and [Cu2(Hhba)4(O-bipy)2]·2(dioxane), where the potentially bridging 4,4'-bipyridine N,N'-dioxide (O-bipy) ligand is employed. Rare cases of mixed carboxylate copper dimer complexes were obtained in the cases of [Cu2(Hhba)3(OAc)(dioxane)]·3.5(dioxane) and [Cu2(Hhba)2(OAc)2(DABCO)2]·10(dioxane), with each structure possessing a 2D network structure. The final compound reported is a simple hydrogen-bonded chain of composition (H0.5DABCO)(H1.5hba), formed from the reaction of H2hba and DABCO.

Competition between O-H and S-H Intermolecular Interactions in Conformationally Complex Systems: The 2-Phenylethanethiol and 2-Phenylethanol Dimers.

Noncovalent interactions involving sulfur centers play a relevant role in biological and chemical environments. Yet, detailed molecular descriptions are scarce and limited to very simple model systems. Here we explore the formation of the elusive S-H···S hydrogen bond and the competition between S-H···O and O-H···S interactions in pure and mixed dimers of the conformationally flexible molecules 2-phenylethanethiol (PET) and 2-phenylethanol (PEAL), using the isolated and size-controlled environment of a jet expansion. The structure of both PET-PET and PET-PEAL dimers was unraveled through a comprehensive methodology that combined rotationally resolved microwave spectroscopy, mass-resolved isomer-specific infrared laser spectroscopy, and quantum chemical calculations. This synergic experimental-computational approach offered unique insights into the potential energy surface, conformational equilibria, molecular structure, and intermolecular interactions of the dimers. The results show a preferential order for establishing hydrogen bonds following the sequence S-H···S < S-H···O ≲ O-H···S < O-H···O, despite the hydrogen bond only accounting for a fraction of the total interaction energy.

Quantum correlations and coherence in a mixed spin- (12,1) Heisenberg dimer under intrinsic decoherence

This research delves into the dynamical behavior of quantum correlations and coherence within a mixed Heisenberg dimer system under the intrinsic decoherence. Our approach involves the application of logarithmic negativity, local quantum uncertainty, and the ℓ 1 norm-based coherence as quantifiers for entanglement, skew information correlations, and quantum coherence in this qubit-qutrit model. Our primary objective is to explore the impact of various factors on the dynamics of quantum correlations and quantum coherence. These factors encompass the initial density matrix and its mixing parameter, the intrinsic decoherence rate (γ), the external magnetic field, as well as intrinsic system parameters, notably the XXZ and uniaxial single-ion anisotropies. Our results demonstrate that the introduction of intrinsic decoherence (ID) significantly erodes quantum resources. Particularly, for high values of the ID rate (γ), excessive damping occurs, leading to the absence of oscillations or a rapid decay of quantum resources, ultimately stabilizing in steady states. Furthermore, the presence of an external homogeneous magnetic field further diminishes quantum resources within the system. However, despite the degradation induced by the combined influence of intrinsic decoherence and high external magnetic field intensities, the judicious selection of the initial density matrix and precise adjustment of the uniaxial single-ion anisotropy enable the preservation of quantum resources within the mixed spin-(1/2, 1) Heisenberg dimer.

An IR spectroscopic investigation of blue shifting C–H⋯Cl hydrogen bonds in room temperature solution: Homomeric and mixed dimers of CHCl3 and CH2Cl2

CH···Cl H-bonded homomeric and mixed dimers of CHCl3 and CH2Cl2 have been studied in room temperature CCl4 solution by observing spectral shift of νC−H fundamental transitions using IR spectroscopy. νC−H bands were found to show blue shift by 1.1 to 3.3 cm−1 upon CH···Cl H-bond formation in all the studied dimers. The findings were reinforced by observing νC−D spectral shifts for the corresponding dimers of the deuterated compounds, i.e., CDCl3 and CD2Cl2. νC−D bands also showed only blue shift within the range of 0.2 to 4.1 cm−1. All the experiments have been performed in another nonpolar solvent (C2Cl4) and the results were in close agreement with each other. Quantum chemical calculations predict multiple stable conformers for each of the dimers studied. In all the cases, the most stable conformers were solely C‒H···Cl H-bonded, confirming the observed νC−H spectral shifts to be brought about by intermolecular C‒H···Cl H-bond formation.

Mixed Dimer Configuration Model in Type D Cluster Algebras

We define a combinatorial model for $F$-polynomials and $g$-vectors for type $D_n$ cluster algebras where the associated quiver is acyclic. Our model utilizes a combination of dimer configurations and double dimer configurations which we refer to as mixed dimer configurations. In particular, we give a graph theoretic recipe that describes which monomials appear in such $F$-polynomials, as well as a graph theoretic way to determine the coefficients of each of these monomials. In addition, we prove that a weighting on our mixed dimer configuration model yields the associated $g$-vector. To prove this formula, we use a combinatorial formula due to Thao Tran (arXiv:0911.4462, 2009) and provide explicit bijections between her combinatorial model and our own.

TCR-NK Cells: A Novel Source for Adoptive Immunotherapy of Cancer.

Antigen-specific retargeting of cytotoxic lymphocytes against tumor-associated antigens has so far remained largely dependent on chimeric antigen receptors (CARs) that can be constructed by the fusion of an extracellular targeting domain (classically an scFv fragment from an antibody) fused with intracellular signaling domains to trigger activation of T or NK cells. A major limitation of CAR-based therapies is that this technology allows only for targeting antigens that would be located on the surface of a target cell while non-surface antigens that constitute about ¾ of all human genes stay out-of-reach. The targeting of non-surface antigens is only possible by using the inherent mechanisms of the T cell receptor (TCR). However, introducing a second TCR into T cells via genetic modification has been problematic due to the heterodimeric nature of the TCR ligand-binding domain that is composed of TCR α and β chains. It has been observed that the delivery of a second TCR α/β pair to may lead to mispairing of new TCR chains with the endogenously expressed ones and create mixed TCR dimers which has negatively affected the advancement of TCR-based T cell therapies. Recently, Natural Killer (NK) cells have been put forward as effectors for TCR gene therapy. Since NK cells do not endogenously express TCR chains, this seems to be an infallible method in circumventing the mispairing problem. Moreover, the similarity of intracellular signaling pathways and mechanisms of cytotoxicity between NK and T cells makes sure that the triggering of antigen-specific responses by the TCR/CD3 complex can be used to induce antigen-specific cytotoxicity by TCR-modified NK cells (TCR-NK). This review aims to overview the initial studies on TCR-NK cells, identify open questions in the field and define its place within the spectrum of adoptive immunotherapy approaches that rely on cytotoxic lymphocytes.

Elevator transport mechanism in SLC4 transporters: Insights from new inward facing cryo-EM structures of AE1.

The SLC4 transporters are responsible for the transport of various ions, such as HCO3−, CO32−, Cl−, Na+, and NH3+H+, necessary for maintenance of pH, blood pressure and ion homeostasis in the body. Among them, the AE1 transporter protein (Anion Exchanger 1, Band 3, SLC4A1), a Na+-independent Cl−/HCO3− exchanger, has been extensively studied both from theoretical and experimental perspective, due to its peculiarly high rate of transport. An outward facing (OF) open structure of the human AE1 has been previously resolved and substrate binding sites in it have been identified both from computational, functional mutagenesis, and cryoEM studies. However, detailed understanding of the transport mechanism of AE1 and other members of the SLC4 family is hindered by lack of structures of other catalytically relevant states. In the present work we report cryoEM structures of dimers of bovine AE1 (bAE1), which feature inward facing (IF) open monomers. Moreover, mixed dimers where one monomer is in IF and the other - in OF state, were also resolved, indicating independent movement of monomers in the dimers. The new IF and OF states of bAE1 provide unambiguous structural evidence for elevator transport mechanism with a small vertical shift of the core domain with respect to the rigid gate domain. An unexpected elongation of transmembrane helix (TM) 11 and the accompanying reorganization of intracellular loop (IL) 5 from beta-hairpin into alpha-helical geometry is also observed in the IF state. Computational modelling demonstrates different anion dynamics at both sides of the lipid membrane. The small structural reorganization during the OF to IF transition, and the fast anion permeation into the IF and OF cavities of AE1 emerge as possible explanations of the observed high transport rate of this protein.

Glycine Peptide Chain Formation in the Gas Phase via Unimolecular Reactions

Peptide chain formation from amino acids such as glycine is a key step in the emergence of life. Unlike their synthesis by living systems, how peptide chains grow under abiotic conditions is an open question given the variety of organic compounds discovered in various astrophysical environments, comets and meteorites. We propose a new abiotic route in the presence of protonated molecular dimers of glycine in a cold gaseous atmosphere without further need for a solid catalytic substrate. The results provide evidence for the preferential formation of mixed protonated dimers of glycine consisting of a dipeptide and a glycine molecule instead of pure protonated glycine dimers. Additional measurements mimicking a cosmic-ray impact in terms of internal excitation show that a single gas-phase collision induces polymerization via dehydration in both the mixed and pure dimer ions. Peptide chain growth is thus demonstrated to occur via a unimolecular gas-phase reaction in an excited cluster ion.

An Alzheimer’s Disease Mechanism Based on Early Pathology, Anatomy, Vascular-Induced Flow, and Migration of Maximum Flow Stress Energy Location with Increasing Vascular Disease

This paper suggests a chemical mechanism for the earliest stages of Alzheimer's disease (AD). Cerebrospinal fluid (CSF) flow stresses provide the energy needed to induce molecular conformation changes leading to AD by initiating amyloid-β (Aβ) and tau aggregation. Shear and extensional flow stresses initiate aggregation in the laboratory and in natural biophysical processes. Energy-rich CSF flow regions are mainly found in lower brain regions. MRI studies reveal flow stress "hot spots" in basal cisterns and brain ventricles that have chaotic flow properties that can distort molecules such as Aβ and tau trapped in these regions into unusual conformations. Such fluid disturbance is surrounded by tissue deformation. There is strong mapping overlap between the locations of these hot spots and of early-stage AD pathology. Our mechanism creates pure and mixed protein dimers, followed by tissue surface adsorption, and long-term tissue agitation ultimately inducing chemical reactions forming more stable, toxic oligomer seeds that initiate AD. It is proposed that different flow stress energies and flow types in different basal brain regions produce different neurotoxic aggregates. Proliferating artery hardening is responsible for enhanced heart systolic pulses that drive energetic CSF pulses, whose critical maximum systolic pulse energy location migrates further from the heart with increasing vascular disease. Two glymphatic systems, carotid and basilar, are suggested to contain the earliest Aβ and tau AD disease pathologies. A key to the proposed AD mechanism is a comparison of early chronic traumatic encephalopathy and AD pathologies. Experiments that test the proposed mechanism are needed.

Crystallographic Characterisation of Organolithium and Organomagnesium Intermediates in Reactions of Aldehydes and Ketones

AbstractWe report reactions of LiNacNac and NacNacMg(TMP) with common organic substrates (TMP=2,2,6,6‐tetramethylpiperidide). Using bulky β‐diketiminate compound NacNac (Me, Dipp), we have trapped metalated intermediates amenable to X‐ray crystallographic study. LiNacNac and acetone produced the NacNac‐free hexameric diacetone alkoxide [{LiO(MeC(=O)CH2C(Me)2}6]; whereas pinacolone gave the simple monomeric donor–acceptor complex [Li{(MeCN‐2,6‐iPr2C6H3)2CH}{O=C(Me)tBu}]. Benzaldehyde produced dimeric [Li{(MeCN‐2,6‐iPr2C6H3)2CC(=O)Ph}{O=C(Ph)OCH2Ph}]2, where one benzaldehyde molecule has inserted in to the γ‐carbon position of the NacNac ligand, with a molecule of benzyl benzoate derived from a Tishchenko reaction of the aldehyde acting as a terminal donor to lithium. Tetranuclear, mixed dimer [{LiO(MeCN‐2,6‐iPr2C6H3)2CH‐CH(Ph)}2{LiO(PhC(=O)}2] containing the same modified NacNac ligand was the fortuitous product from repeating the reaction of LiNacNac and benzaldehyde in a solution presumably contaminated with benzoic acid. Combining NacNacMg(TMP) with pinacolone affords monomeric heteroleptic [Mg{(MeCN‐2,6‐iPr2C6H3)2CH}{OC(tBu)(Me)CH2C(=O)tBu}] with an aldolate constituting the second anion. Completing the set is dimeric [Mg{(MeCN‐2,6‐iPr2C6H3)2CH}{O(C=CH2)Ph}2], where the enolate derived from acetophenone bridges the magnesium centres.

Vibronic recovering of functionality of quantum cellular automata based on bi-dimeric square cells with violated condition of strong Coulomb repulsion.

Strong Coulomb repulsion between the two charges in a square planar mixed-valence cell in quantum cellular automata (QCA) allows us to encode the binary information in the two energetically beneficial diagonal distributions of the electronic density. In this article, we pose a question: to what extent is this condition obligatory for the design of the molecular cell? To answer this question, we examine the ability to use a square-planar cell composed of one-electron mixed valence dimers to function in QCA in a general case when the intracell Coulomb interaction U is not supposed to be extremely strong, which means that it is comparable with the characteristic electron transfer energy (violated strong U limit). Using the two-mode vibronic model treated within the semiclassical (adiabatic) and quantum-mechanical approaches, we demonstrate that strong vibronic coupling is able to create a considerable barrier between the two diagonal-type charge configurations, thus ensuring bistability and polarizability of the cells even if the Coulomb barrier is not sufficient. The cases of weak and moderate Coulomb repulsion and strong vibronic coupling are exemplified by consideration of the cation radicals of the two polycyclic derivatives of norbornadiene [C12H12]+ and [C17H16]+ with the terminal C=C chromophores playing the role of redox sites. By using the detailed ab initio data, we reveal the main characteristics of the bi-dimeric cells composed of these molecules and illustrate the pronounced effect of the vibronic recovery clearly manifesting itself in the shape of the cell-cell response function. Revealing such "vibronic recovery" of strong localization when the strong U limit is violated suggests a way to a significant expansion of the class of molecular systems suitable as QCA cells.

Dimeric phenanthrenoids: possible biogenetic pathway and missing compounds

Secondary metabolites extracted from plants have historically been critical for drug discovery, but their isolation involves expensive and complicated procedures in terms of time and labor resources. Thus, the biogenetic pathway offers the possibility of identifying specific compounds that have not yet been isolated and predicting their isolation from specific natural sources. In plants, biphenanthrenes represent a relatively small group of aromatic secondary metabolites that are considered as important taxonomic markers with promising biological activities. To date, 38 mixed phenanthrenoid dimers have been identified, the biosynthesis of which involves the radical coupling of the two subunits, namely, a phenanthrene and a dihydrophenanthrene. For each of the compounds, it is possible to identify the single phenanthrenic and dihydrophenanthrenic units constituting the considered dimer. Based on the biogenetic pathway, it is possible to identify 19 phenanthrenes and 17 dihydrophenanthrenes, and to distinguish those already known from those not yet isolated. By comparing the results of the possible biosynthetic pathway for each compound with the data in the literature, it is possible to identify three known phenanthrenes and seven known dihydrophenanthrenes, as well as eleven new phenanthrenes and five new dihydrophenanthrenes, and to identify from which plant it is possible to isolate them. This could direct the work of researchers seeking to identify known or new molecules useful for their possible biological properties, and ultimately, to confirm the veracity of the proposed and generally accepted biosynthetic pathway.

Author Correction: Highly efficient double ionization of mixed alkali dimers by intermolecular Coulombic decay

Author Correction: Highly efficient double ionization of mixed alkali dimers by intermolecular Coulombic decay

Characterization of Competing Halogen- and Hydrogen-Bonding Motifs in Simple Mixed Dimers of HCN and HX (X = F, Cl, Br, and I).

This work performs the first systematic comparison of hydrogen- and halogen-bonded configurations of the HCN/HX mixed dimer, where X = F, Cl, Br, and I. Eleven different minima have been characterized for these four heterogeneous dimers near the CCSD(T) complete basis set (CBS) limit. For each complex, two different hydrogen-bonded minima were identified: the global minimum where HX acts as the hydrogen bond donor and a local minimum where HX acts as the hydrogen bond acceptor. A halogen-bonded local minimum was also identified for all but the fluorine mixed dimer. To the best of our knowledge, three of the minima are identified here for the first time. The hydrogen- and halogen-bonded local minima of each complex become more energetically competitive with the global minimum as the atomic radius of the halogen atom increases. CCSD(T) relative energies of the hydrogen-bonded local minima computed near the CBS limit decrease from 4.5 kcal mol-1 for HCN/HF to 2.9, 2.4, and 1.2 kcal mol-1 for X = Cl, Br, and I, respectively. Corresponding relative energies for the halogen-bonded local minima range from 4.0 kcal mol-1 for X = Cl to 2.7 kcal mol-1 for X = Br and to as little as 0.5 kcal mol-1 X = I. Harmonic vibrational frequency shifts reported here suggest that it may be feasible to differentiate between the various minima for X = Cl, Br, and I via spectroscopic analysis, as was the case for the HCN/HF dimer.

Mechanism of Bloom syndrome complex assembly required for double Holliday junction dissolution and genome stability

The RecQ-like helicase BLM cooperates with topoisomerase IIIα, RMI1, and RMI2 in a heterotetrameric complex (the "Bloom syndrome complex") for dissolution of double Holliday junctions, key intermediates in homologous recombination. Mutations in any component of the Bloom syndrome complex can cause genome instability and a highly cancer-prone disorder called Bloom syndrome. Some heterozygous carriers are also predisposed to breast cancer. To understand how the activities of BLM helicase and topoisomerase IIIα are coupled, we purified the active four-subunit complex. Chemical cross-linking and mass spectrometry revealed a unique architecture that links the helicase and topoisomerase domains. Using biochemical experiments, we demonstrated dimerization mediated by the N terminus of BLM with a 2:2:2:2 stoichiometry within the Bloom syndrome complex. We identified mutations that independently abrogate dimerization or association of BLM with RMI1, and we show that both are dysfunctional for dissolution using invitro assays and cause genome instability and synthetic lethal interactions with GEN1/MUS81 in cells. Truncated BLM can also inhibit the activity of full-length BLM in mixed dimers, suggesting a putative mechanism of dominant-negative action in carriers of BLM truncation alleles. Our results identify critical molecular determinants of Bloom syndrome complex assembly required for double Holliday junction dissolution and maintenance of genome stability.

Anharmonicity modeling in hydrogen bonded solvent dimers

Harmonic and anharmonic frequencies of dimers and mixed dimers of water, methanol and benzene were computed and the results were critically analysed to investigate the anharmonicity of the normal mode vibrations within density functional theory (DFT) with empirically included Grimme correction for dispersion (D3). From several options, the B3LYP-D3/6-31++G* level of theory was selected as a good compromise between accuracy and calculation speed, suitable for future modeling of larger solvent clusters. The obtained raw harmonic and anharmonic second-order perturbation theory of vibrational frequencies (VPT2) were additionally scaled using a two-range procedure (below and above 2000 cm−1) and compared with available experimental values for the studied dimers. Additionally, the Morse and 4th order polynomial fittings of small normal mode deflections from the equilibrium geometry were used to model anharmonicity of the studied dimers. Compared to B3LYP-D3, the VPT2 vibrations calculated with APFD and M06-2X functionals very poorly model the anharmonicity of the H-bonded dimers. The surprising observation was related to the performance of CCSD/6-31++G* and CCSD(T)/6-31++G* in predicting harmonic frequencies of H-bonded dimers of water, water-methanol and methanol-water of similar quality, as compared to B3LYP-D3/6-31++G*. The obtained results suggest using of B3LYP-D3/6-31++G* scaled harmonic frequencies for the larger solvent clusters as a good alternative to anharmonic frequencies.

Aliovalent substitution in phosphide‐based materials – Crystal structures of Na10AlTaP6 and Na3GaP2 featuring edge‐sharing EP4 tetrahedra (E=Al/Ta and Ga)

AbstractRecently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. Much less is known about the corresponding sodium‐containing compounds, and during investigations aiming for sodium phosphidotrielates, two new compounds have been obtained. The sodium phosphidoaluminumtantalate Na10AlTaP6, at first obtained as a by‐product from the reaction with the container material, crystallizes in the monoclinic space group P21/n (no. 14) with lattice parameters of a=8.0790(3) Å, b=7.3489(2) Å, c=13.2054(4) Å, and β=90.773(2)°. The crystal structure contains dimers of edge‐sharing [(Al0.5Ta0.5)P4] tetrahedra with a mixed Al/Ta site. DFT calculations support the presence of this type of arrangement instead of homonuclear Al2P6 or Ta2P6 dimers. The 31P and 23Na MAS NMR as well as the Raman spectra confirm the structure model. The assignment of the chemical shifts is confirmed applying the DFT‐PBE method on the basis of the ordered structural model with mixed AlTaP6 dimers. The sodium phosphidogallate Na3GaP2 crystallizes in the orthorhombic space group Ibam (no. 72) with lattice parameters of a=13.081(3) Å, b=6.728(1) Å, and c=6.211(1) Å and is isotypic to Na3AlP2. Na3GaP2 exhibits linear chains of edge‐sharing 1∞[GaP4/2] tetrahedra. For both compounds band structure calculations predict indirect band gaps of 2.9 eV.

Regulation of drug release performance using mixed doxorubicin-doxorubicin dimer nanoparticles as a pH-triggered drug self-delivery system

A mixed drug self-delivery system (DSDS) with high drug content (>50%) was developed to regulate pH-triggered drug release, based on two doxorubicin (DOX)-DOX dimmers: D-DOXADH and D-DOXcar conjugated with acid-labile dynamic covalent bonds (hydrazone and carbamate, respectively) and stabilized with PEGylated D-DOXADH (D-DOXADH-PEG). Owing to the different stability of the dynamic covalent bonds in the two dimers and the noncovalent interaction between them, pH-triggered drug release could be easily regulated by adjusting the feeding ratios of the two DOX-DOX dimers in the mixed DSDS. Similar in vitro cellular toxicity was achieved with the mixed DSDS nanoparticles prepared with different feeding ratios. The mixed DSDS nanoparticles had a similar DOX content and diameter but different drug releasing rates. The MTT assays revealed that a high anti-tumor efficacy could be achieved with the slow-release mixed DSDS nanoparticles.