Understanding the forces governing hydrophobically driven inclusion provides a path for aimed utilization of non-polar synthons and provides insights into the related hydration thermodynamics. To ...shed light on the factors that determine the stability of complexes with large, rigid guests, we studied the temperature and the solvent effect on the hosting of diamantane alcohols with heptameric and octameric cyclodextrins and cucurbiturils. The smaller cyclodextrin was a more efficient binder of the explored guests, while inclusion within
γ-CD
was observed solely in water. The higher stability of
β-CD
complexes in this solvent (298 K) was due to the strongly exothermic, entropically opposed inclusion, whereas endothermic hosting of alcohols by
γ-CD
was observed in all cases except for diamantan-1-ol. The entropically more demanding dehydration of the
β-CD
cavity hence masks the positive entropy changes accompanying the removal of guest-hydrating water. A strong decrease in Δ
r
H
°(
T
) for all studied systems was noticed in water. In the case of cyclodextrins, the phenomenon shifts the driving force from completely or predominantly classical towards non-classical. Conversely, due to the particularly poor structuring of cucurbituril-confined water, the binding remained essentially non-classical over the explored temperature range. Unlike complexation in water, the complexation in formamide and ethylene glycol was entirely enthalpy-driven and weakly temperature-dependent.
Guest hydration sphere melting shifts cyclodextrin inclusion thermodynamics from classical towards non-classical, where with cucurbiturils it is enthalpy-driven despite
. Binding with
γ-CD
in organic solvents is enthalpy-driven with
.
With an ever-growing application of inclusion complexes of cyclodextrins (CDs) and other hydrophobic guests in pharmaceutical industry and other scientific and industrial fields, the demand for ...deeper understanding of effects defining their stability increases. In this work we investigated the formation of inclusion complexes of diamondoid derivatives containing the ammonium moiety with β- and γ-cyclodextrins using NMR, ITC and conductometric titrations. The adamantane- and diamantane-based guests containing one ammonium group formed stable 1 : 1 complexes with β-CD, whereas only the diamantane derivative interacted with γ-CD. The thermodynamics of the binding processes was characterized in detail by means of ITC and the origin of the enthalpic and entropic contributions was discussed. Structural features of the complexes were deduced from the data gathered by NOESY NMR and computational studies revealing the key interactions within the inclusion complexes. Surprisingly, the diammonium derivative did not exhibit any affinity towards inclusion in the cavity of the investigated CDs, which was in strong contrast with its behavior when cucurbituril was used as a host. By providing comprehensive structural and thermodynamic data, this study gives a firm basis for understanding the effects defining the stability of inclusion complexes of charged diamondoid guests with cyclodextrins.
A hydrophobic tornado - complexation of diamondoid ammonium salts with cyclodextrins in water.
Seven complexes, Ni(NCS)
2
(isn)
2
(H
2
O)
2
·2H
2
O (
1
), Ni(NCS)
2
(isn)
2
(H
2
O)
2
(
2
), Ni(NCS)
2
(isn)
3
(H
2
O)·2.5H
2
O (
3
), Ni(NCS)
2
(isn)
3
(H
2
O)·3Ni(NCS)
2
(isn)
4
·9H
2
O (
4
), ...Ni(NCS)
2
(isn)
4
·3H
2
O (
5
), Ni(NCS)
2
(isn)
4
·2(isn) (
6
) and Ni(NCS)
2
(isn)
4
·1.25H
2
O (
7
), of Ni(
ii
) thiocyanate with isonicotinamide (isn = pyridine-4-carboxamide) and water as ligands of biological importance were prepared in aqueous solutions through crystal screening by variation of the isonicotinamide concentration. They were characterized by the single-crystal X-ray diffraction method and DFT calculations, while
1-6
were characterized also by NMR and IR spectroscopy and elemental and thermal analyses. In all complexes, the nickel atom is octahedrally coordinated with two thiocyanate N atoms but with different number of isonicotinamide N and water O atoms. The R
4
6
(12) and R
4
6
(16) hexamers were found in
1
, R
2
4
(8) tetramer and R
2
2
(8) dimer in
2
, while very complex hydrogen bonding ring patterns R
2
4
(8), R
2
2
(10), R
3
4
(14) and R
6
10
(24) were observed in
3
. In
4
, R
4
6
(16) and R
6
6
(20) hexamers were formed as well as typical head-to-head amide-amide hydrogen bond R
2
2
(8) dimers in a combination with two R
3
4
(10) tetramers. R
2
4
(8) cyclic water tetramers linked in zigzag hydrogen bonded chains, carboxamide catemer C(4) chains with the R
6
8
(24) ring and two fused rings R
2
3
(12) and R
2
2
(16) were found in
5
. A 2D corrugated sheet network in the (002) planes with a combination of R
4
4
(16), R
4
6
(16), R
6
6
(24) and R
6
8
(24) rings were formed in
6
. DFT calculations revealed that altered metal complex stoichiometries originate in different ligand affinities towards nickel, isn > SCN
−
> H
2
O. Only neutral complexes were investigated so the nickel : thiocyanate ratio was always 1 : 2 while the concentration of isonicotinamide strongly influenced the number of coordinated isn ligands. The final 3D crystal structures emerged as a compromise between the nucleation process, reactant ratios, ligand affinities and intermolecular interactions in the crystal packing.
Crystal screening by varying isonicotinamide content added to Ni(
ii
) thiocyanate in water led to seven nickel complexes, whose structure and altered stoichiometries were analyzed by X-ray diffraction, NMR and IR spectroscopies, and DFT calculations.
Six novel 1 : 2 complexes of silver(
i
) nitrate with 2,5-, 2,6- and 3,5-dihalopyridines (halo stands for chlorine and bromine) were prepared by the reaction of an aqueous solution of AgNO
3
and the ...corresponding pyridine derivative in a water-alcohol solution. In spite of having analogous empirical formulae, they reveal intriguing structural differences, except Ag(NO
3
)(2,5-Cl
2
py)
2
n
(
1
) and Ag(NO
3
)(2,5-Br
2
py)
2
n
(
4
), which are isostructural. In contrast, Ag(NO
3
)(3,5-Cl
2
py)
2
2
(
3
) is dimeric, while its Br analogue Ag(NO
3
)(3,5-Br
2
py)
2
n
(
6
) is polymeric in nature, being the only complex with no halogen halogen interactions. Lastly, both Ag(NO
3
)(2,6-Cl
2
py)
2
(
2
) and Ag(NO
3
)(2,6-Br
2
py)
2
(
5
) consist of monomeric molecules, with dissimilar interaction patterns among units linking chains into different 3D structures. In addition, all isolated complexes were identified by elemental analysis and characterized in solution by multinuclear NMR spectroscopy (
1
H,
13
C,
15
N) and IR and mass spectrometry. DFT calculations verified the predominant tendency of the Ag
+
ions to bind two pyridine nitrogen atoms and one nitrate ion in their complexes and confirm that their supramolecular structure is a compromise between competing weak intramolecular interactions and steric constrains.
The crystal structures of six novel Ag
+
complexes with NO
3
−
and dihalopyridines revealed intriguing differences that were interpreted by DFT calculations.
A novel synthetic approach toward a poorly explored bioorganometallic consisting of ferrocene-1,1′-diamine bearing structurally and chirally diverse amino acid sequences is reported. Until now, ...ferrocene-1,1′-diamine was suitable for accommodating only identical amino acid sequences at its N-termini, leading to the symmetrically disubstituted homochiral products stabilized through a 14-membered intramolecular hydrogen-bonded ring as is seen in antiparallel β-sheet peptides. The key step of the novel synthetic pathway is the transformation of Ac-Ala-
-Fn-
OH (
5
) (Fn = 1,1′-ferrocenylene) to orthogonally protected Ac-Ala-
-Fn-
Boc (
7
). The spectroscopic analysis (IR, NMR, CD) of the novel compounds, corroborated with DFT studies, suggests the interesting feature of the ferrocene-1,1′-diamine scaffold. The same hydrogen-bonding pattern,
i.e.
a 14-membered hydrogen-bonded ring, was determined both in solution and in the solid state, thus making them promising, yet simple scaffolds capable of mimicking β-sheet peptides.
In vitro
screening of potential anticancer activity in Hep G2 human liver carcinoma cells and Hs 578 T human breast cancer cells revealed a cytotoxic pattern for novel compounds (150-500 μM) with significantly decreased cell proliferation.
The first example of an orthogonally protected ferrocene-1,1′-diamine based peptidomimetic with a stable intramolecular hydrogen bond pattern comprised of two β-turns is reported.
Reakcijom srebrova(I) nitrata s mono- i dihalogen derivatima piridina u molarnom omjeru 1 : 2 u smjesi vode i alkohola priređeno je 12 novih kompleksa srebra(I) opće formule Ag(NO3)(Xnpy)2, X = Cl, ...Br, I; n = 1 – 2. Pripravljeni kompleksni spojevi identificirani su pomoću elementne analize, dok je njihova struktura u otopini okarakterizirana tehnikama višenuklearne spektroskopije NMR (1H, 13C, 15N, 109Ag) i spektrometrije masa. Kompleksi su u čvrstom stanju okarakterizirani spektroskopijom IR, a kristalna i molekulska struktura im je određena metodama rentgenske strukturne analize.
Molekule liganda su u svim kompleksima na srebrov(I) ion vezane preko atoma dušika piridinskog prstena. U koordinacijskoj sferi srebra(I) dokazan je i nitratni ion koji ovisno o načinu koordiniranja na srebro omogućava stvaranje koordinacijskih polimera ili supramolekulskih struktura. Koordinacijski broj srebra kod sintetiziranih spojeva varira između tri, četiri, pet ili šest i to čak ponegdje i unutar istog spoja. Pored kovalentnih veza, Ag–N i Ag–O, u strukturama su pronađene i nekovalentne interakcije (vodikove i halogenske veze te π···π interakcije) koje pridonose konačnoj dimenzionalnosti spoja. Slaba veza Ag–Ag otkrivena je u kompleksu s 3-Ipy kao ligandom. Priređeni spojevi pokazuju bolju antibakterijsku aktivnost u uvjetima in vitro spram Gram-negativnih nego spram Gram-pozitivnih bakterijskih vrsta.
Twelve 1:2 complexes of silver(I) nitrate with mono- and dihalopyridine of the general formula Ag(NO3)(Xnpy)2, X = Cl, Br, I; n = 1–2, were prepared by reaction of AgNO3 and corresponding pyridine derivative in water-alcohol solution. All synthesized complexes were identified by elemental analysis and characterized in solution by multinuclear NMR spectroscopy (1H, 13C, 15N, 109Ag) and mass spectrometry. In solid state the complexes were characterized by IR spectroscopy, while their crystal and molecular structures were revealed by single crystal X-ray analysis.
It was established that in all complexes, besides pyridine nitrogen atoms, the oxygen atoms belonging to nitrate ion are also coordinated to silver ion thus providing not only different coordination numbers of Ag(I) which vary from three, four, five and six but also a formation of coordination polymers or supramolecular structures. It is interesting that in the molecule of one complex, which is dinuclear, there are even two differently coordinated silver ions (3, 4). Beside covalent Ag–N and Ag–O bonds present in complex molecules, there are various non-covalent interactions such as hydrogen bonding, halogen bonds and halogen-halogen interactions thus contributing to final dimensionality. Moreover, a weak Ag–Ag bonding was determined in complex with 3-Ipy as a ligand. In vitro tests of all complexes gave better antibacterial activity against Gram-negative than Gram-positive strains.
•Longer treatments at higher temperatures produce less inverted CoFe2O4 particles.•Lower temperatures and shorter firing times resulted in higher coercivities.•Firing time has a lower influence on ...the results than treatment temperature.
Several studies have shown the exceptional responses of spinel cobalt ferrites as advanced ceramics. Nevertheless, there is still a gap in the literature regarding the effect of synthesis parameters on the properties of the spinel products. This work aims to correlate temperature and annealing time with the structural, optical, and magnetic properties of CoFe2O4. Precursors were prepared by sol–gel and thermally treated at 550, 650, and 750 °C for 2, 4, and 6 h. The microstructure was characterized by XRD, BET, SEM, and Raman spectroscopy. Treatment longer than 6 h at temperatures higher than 650 °C produced less inverted nanoparticles with larger crystallites. Although the initial annealing conditions did not influence the ferrites bandgap, VSM results showed an opposite response. The maximum in coercivity (1654.25 Oe) was obtained in the sample annealed in the shortest time (2 h) and at the lowest temperature (550 °C). Statistical analyses prove that despite not affecting the results in the same manner, both initial conditions affected the CoFe2O4 properties. Our results open up the possibility of improving the CoFe2O4 manufacturing process for commercial exploration.
This work reports for the first time a highly efficient single‐crystal cesium tin triiodide (CsSnI3) perovskite nanowire solar cell. With a perfect lattice structure, low carrier trap density ...(≈5 × 1010 cm−3), long carrier lifetime (46.7 ns), and excellent carrier mobility (>600 cm2 V−1 s−1), single‐crystal CsSnI3 perovskite nanowires enable a very attractive feature for flexible perovskite photovoltaics to power active micro‐scale electronic devices. Using CsSnI3 single‐crystal nanowire in conjunction with highly conductive wide bandgap semiconductors as front‐surface‐field layers, an unprecedented efficiency of 11.7% under AM 1.5G illumination is achieved. This work demonstrates the feasibility of all‐inorganic tin‐based perovskite solar cells via crystallinity and device‐structure improvement for the high‐performance, and thus paves the way for the energy supply to flexible wearable devices in the future.
Efficient solar cell is achieved based on single‐crystal cesium tin triiodide nanowires with a long carrier lifetime and a large carrier mobility. The unique front‐surface‐field device structure of single‐crystal nanowire solar cells is proven to be an effective means of enhancing the carrier extraction and effectively boosting efficiency.
The pathogenesis of Alzheimer's disease (AD) is characterized by overproduction, impaired clearance, and deposition of amyloid-β peptides (Aβ) and connected to cholesterol homeostasis. Since the ...blood-brain barrier (BBB) is involved in these processes, we investigated effects of the retinoid X receptor agonist, bexarotene (Bex), and the peroxisome proliferator-activated receptor α agonist and antioxidant, astaxanthin (Asx), on pathways of cellular cholesterol metabolism, amyloid precursor protein processing/Aβ production and transfer at the BBB in vitro using primary porcine brain capillary endothelial cells (pBCEC), and in 3xTg AD mice. Asx/Bex downregulated transcription/activity of amyloidogenic BACE1 and reduced Aβ oligomers and ~80 kDa intracellular 6E10-reactive APP/Aβ species, while upregulating non-amyloidogenic ADAM10 and soluble (s)APPα production in pBCEC. Asx/Bex enhanced Aβ clearance to the apical/plasma compartment of the in vitro BBB model. Asx/Bex increased expression levels of ABCA1, LRP1, and/or APOA-I. Asx/Bex promoted cholesterol efflux, partly via PPARα/RXR activation, while cholesterol biosynthesis/esterification was suppressed. Silencing of LRP-1 or inhibition of ABCA1 by probucol reversed Asx/Bex-mediated effects on levels of APP/Aβ species in pBCEC. Murine (m)BCEC isolated from 3xTg AD mice treated with Bex revealed elevated expression of APOE and ABCA1. Asx/Bex reduced BACE1 and increased LRP-1 expression in mBCEC from 3xTg AD mice when compared to vehicle-treated or non-Tg treated mice. In parallel, Asx/Bex reduced levels of Aβ oligomers in mBCEC and Aβ species in brain soluble and insoluble fractions of 3xTg AD mice. Our results suggest that both agonists exert beneficial effects at the BBB by balancing cholesterol homeostasis and enhancing clearance of Aβ from cerebrovascular endothelial cells.
•Asx exerts beneficial effects similar to Bex in brain capillary endothelial cells.•Non-amyloidogenic APP processing is enhanced via BACE1 and ADAM10 modulation.•ABCA1 is upregulated and cellular cholesterol efflux is stimulated involving nuclear receptor-dependent mechanisms.•LRP-1 is up regulated along with augmented Aβ uptake/transcytosis.•Silencing of LRP-1 or inhibition of ABCA1 reverses effects of Asx and Bex on APP processing/Aβ species.•Asx and Bex considerably reduce cerebral and cerebrovascular Aβ load in vivo in 3xTg AD mice.
The nuclear symmetry energy plays a key role in determining the equation of state (EoS) of dense, neutron-rich matter, which connects the atomic nuclei with the hot and dense matter in universe, thus ...has been the subject of intense investigations in laboratory experiments, astronomy observations and theories. Various probes have been proposed to constrain the symmetry energy and its density dependence. Currently, the extensive data yield already a good and consistent constraint to the symmetry energy (Esym(ρ)) at saturation density, but do not yet give a consistent result of one critical EoS parameter, L, the density dependence of the symmetry energy. In this work, we report a new probe of L at saturation density. A good linear correlation is found between L and the charge changing cross section difference (Δσcc) of mirror nuclei 30Si-30S for both the Skyrme-Hartree-Fock theory (SHF) and covariant (relativistic) density functionals (CDF). We found that the pairing effect for this mirror pair is essential to get a consistent correlation between L and Δσcc in both the SHF and CDF. Here, the cross sections are calculated on the same target and at the same energy using the zero-range optical-limit Glauber model. The linearity is found to be in the same precision as those found between L and neutron skin thickness or proton radius difference.
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