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According to our search of the Cambridge Structural Database, a huge number of crystal structures involving intramolecular C S⋯O S(C) interactions were extracted. The largest proportion of these interactions in the crystals shows rather good linearity and short interatomic S⋯O distances. Then, intramolecular C S⋯O S(C) interactions in three representative organic molecules, i.e. sulfamethizole, thioindirubin, and thiazolo-pyridinium methide, were investigated using density functional theory calculations at the M06-2x level. The effects of different substituents and intermolecular hydrogen bonds on these interactions were also examined. The presence of both electron-withdrawing and electron-donating substituents into the donor moiety tends to strengthen intramolecular S⋯O bonds, while the formation of intermolecular hydrogen bonds has a complex influence. To gain a deeper understanding of the nature and strength of these interactions, the analyses of atom in molecules, noncovalent interaction index, and natural bond orbital were undertaken. Intramolecular chalogen bonds are weak electrostatic interactions and play a key role in controlling the crystal forms of relevant organic compounds, frequently supported by intermolecular hydrogen bonds. [ABSTRACT FROM AUTHOR]

To elucidate the efficient removal and reliable storage of radioactive iodine for ionic liquids, halogen bonds in the complexes of I 2 with a series of ion pairs were investigated at the M06-2x level of theory in this work. Albeit halogen bonds in these complexes are somewhat weaker than those in the systems of bare anions, these interactions still belong to strong halogen bonds and show some covalent character. The strength of these interactions deceases in the following order: [Cl] − ≈ [Br] − ≈ [I] − > [Ac] − ≈ [NO 3 ] − > [BF 4 ] − , consistent with the experimentally determined trend of the removal efficiency for corresponding ionic liquids. In addition, the electrostatic potential, atoms in molecules, and charge transfer analyses were also undertaken for the complexes under study, to gain a deeper understanding of the nature of these interactions. [ABSTRACT FROM AUTHOR]

Highlights: [•] Substituents in electron donors have a slight effect on halogen bonding. [•] The presence of transition metals leads to much stronger halogen bonds. [•] Crystallographic evidence has been obtained from the CSD. [ABSTRACT FROM AUTHOR]

Highlights: [•] Electron-donating substituents lead to stronger halogen bonds. [•] X⋯N interactions play a key role in XB-based crystal engineering. [•] Experimental evidence of the interactions was obtained from CSD. [ABSTRACT FROM AUTHOR]

Highlights: [•] Weak energetic effects are observed in the studied crystal structures. [•] Calculated energetic results agree well with the geometric features. [•] Energetic effects are much more complicated in crystal structures. [Copyright &y& Elsevier]

Abstract: In this work, a systematic theoretical investigation on a series of dimeric complexes formed between MH2 and HX has been carried out by employing correlated ab initio methods. It was shown that besides dihydrogen bonds, there also exists novel noncovalent X⋯H interactions between the two molecules, which have similar characteristics to traditional halogen bonds. Upon complexation, the Hend to elongate in all cases, concomitant with red-shifts of the Hing frequencies. X⋯H interaction energies, calculated at the MP2/aug-cc-pvtz level, range from −2.11 to −11.78kJ/mol; the interactions are much weaker than corresponding dihydrogen bonds. The major stabilization source of dihydrogen and halogen bonds arises from the electrostatic force, while charge-transfer force plays a minor role in the formation of the complexes. AIM analyses further confirm the presence of X⋯H interactions in the systems, and the electron density at bond critical points correlates fairly well with the interaction energy. [Copyright &y& Elsevier]

[Display omitted] • Several complexes in which double ChB and XB interactions coexist were studied. • Weak energetic effects are found between the two kinds of interactions. • Many computational tools were used to characterize these σ-hole interactions. The interplay between double chalcogen-bonding interactions and halogen bonds that coexist in the complexes of ditopic chalcogenazolo-pyridine modules was investigated through the analysis of the crystal structures collected and theoretical calculations. Weak energetic effects are observed in the studied complexes, and these two interactions thus show some additive characters, which can be ascribed to the formation of double interactions with a cyclic motif. The computational tools of atoms in molecules, noncovalent interaction index, and natural bond orbital were also used to characterize the interactions as well as to analyze how these two interactions mutually influence each other. [ABSTRACT FROM AUTHOR]

• Decorin was stably coated on the surface of titanium by polydopamine. • Decorin-coated titanium surface can inhibit the functions of osteosarcoma cells by inducing apoptosis. • The surface can also enhance the proliferation of pre-osteoblasts in vitro. • The surface is potentially useful for anti-osteosarcoma orthopaedic implant. Osteosarcoma is the most common bone sarcoma in adolescents. Decorin (DCN) has been proposed to be a new anti-osteosarcoma therapeutic strategy. Our previous study has loaded decorin on titanium (Ti) surface by polydopamine (DOPA) as an anchor to enhance osseointegration. In this study, we investigated the effect of decorin-coated Ti substrates (TI-DOPA-DCN) on the oncogenic potential of osteosarcoma cells SAOS-2. The substrates were placed in 24-well plates for cell culture. Cell viability was determined by Cell Counting Kit-8 (CCK8) assay. Apoptosis was evaluated by DAPI staining and Annexin V-FITC/PI double staining analysis. Cell cycle was analyzed by flow cytometry. Cell migration and invasion were evaluated by Transwell assay. For co-culture, the pre-osteogenic cells MEC3T3-E1 and osteosarcoma cells SAOS-2 were stained with cell membrane fluorescent dyes, and then mixed (1:1) for co-culture. The cells were observed under a fluorescence microscope at four time points of 24, 48, 72, and 96 h. The results showed that TI-DOPA-DCN substrate can selectively inhibit cell proliferation of osteosarcoma cells but not pre-osteoblasts. However, the cell cycle of SAOS-2 was not affected by TI-DOPA-DCN substrates. Both DAPI staining and Annexin V-FITC/PI double staining analysis revealed that TI-DOPA-DCN substrates induced apoptosis of osteosarcoma cells. Transwell assay showed that TI-DOPA-DCN substrates inhibited invasion and migration of osteosarcoma cells. Moreover, TI-DOPA-DCN substrates inhibited the growth of osteosarcoma cells but promoted that of pre-osteoblasts in the coculture system. Taken together, these findings suggested that decorin coating on Ti surface simultaneously inhibited the oncogenic potential of osteosarcoma cells but enhanced cell growth of pre-osteoblasts, which could be applied to surface modification of Ti orthopedic implant. [ABSTRACT FROM AUTHOR]

Poly-tetrafluoroethylene (PTFE) is a well-known solid lubricant, but its poor wear resistance limits its tribological applications. Certain carbonaceous fillers reduce PTFE wear rate by up to 4000-fold with no sacrifice of the friction coefficient; whereas the responsible mechanisms remain unclear. We systematically studied the effects of three graphene fillers with different aggregate strengths (graphene nanoplates, few-layer graphene and single-layer graphene) on the wear resistance of graphene-PTFE composites. The results found (1) graphene of weak aggregate strength outperform that of strong aggregate strength by 100 times in wear reduction, (2) strong correlations between wear rate, tribofilm carboxylate signal intensity and filler-matrix area per unit composite mass. The carboxylate signals likely correspond to chemical bonding between mechanochemically degraded PTFE, graphene and the steel counterface within highly crosslinked and adherent transfer films and worn polymer surfaces. Results in this study support two independent (primary versus secondary) wear reduction hypotheses in literature which were further backed by DFT simulations of filler-matrix interactions, TEM/EDS analysis of wear debris, SEM/EDS images of the polymer surfaces, and environmental test results in a dry argon (Ar) atmosphere. The results of this paper are also of instructive value for the development of solid lubricants with highly controllable wear characteristics. [Display omitted] [ABSTRACT FROM AUTHOR]

We novelly designed and synthesized a set of fluorinated diphenyl-diketopyrrolopyrrole (DPP) compounds by varying the position and amount of fluorine atom, and to the best of our knowledge, it is the first time a difluoromethyl group and perfluoroalkyl chains had been introduced into the DPP unit in good yields. We investigate the optical/electrochemical properties of all the compounds. Density functional theory (DFT) calculations were applied to explore orbital energy value of these compounds. The results demonstrated that the perfluorocarbon chains substituted DPPs with larger red-shift in both absorption and emission spectra and narrower bandgap. [ABSTRACT FROM AUTHOR]

Two novel 2,1,3-benzothiadiazole derivatives, used as colorimetric and fluorescent sensors for fluoride ion were designed, synthesized and characterized. These sensors contained single hydrogen-bond functional groups, which acted as interacting sites for fluoride ion. Both sensors displayed a red color in dimethyl sulfoxide solution. Binding studies revealed that they showed noticeable colorimetric and fluorescent responses only to F − among the eight anions tested (F − , Cl − , Br − , I − , AcO − , H 2 PO 4 − , HSO 4 − and NO 3 − ). 1 H NMR titration proved that the interaction between compounds and fluoride ion: hydrogen bond at low fluoride ion concentration, deprotonation at high fluoride ion concentration. Moreover, those compounds showed high sensitivity and selectivity for fluoride ion by inhibiting the excited state intramolecular proton transfer processes, and the detective processes could be followed by direct visual observation. [ABSTRACT FROM AUTHOR]

The geometric, electronic, optical properties, thermodynamic stability, and work function of Li-doped g-C 3 N 4 monolayer were investigated by the first-principles calculation. It was found that the Li atoms were preferentially substituted the open-hollow sites of g-C 3 N 4 . Interestingly, the “odd” number of Li doped g-C 3 N 4 showed metallic properties, while the “even” number of Li atoms widened the band gap of g-C 3 N 4 . The HOMO and LUMO distributions reveal that the active sites located at edge N and C atoms for both pristine and the Li-doped g-C 3 N 4 . In addition, thermodynamic analysis showed that the doped Li atoms reduced the thermodynamic stability of g-C 3 N 4 monolayer sheets. [ABSTRACT FROM AUTHOR]

A multifunctional hypothesis of filler selection for PTFE suggests ultralow wear (10−7 mm3/Nm) depends on the filler's ability to both support the normal load by being large in size and to induce favorable tribochemistry by being weak in aggregate strength. This study is the first to test the independent effects of preferential load support and tribochemistry on PTFE wear by studying the wear reducing properties of a porous GaN fiber, a fully dense SiO 2 fiber and microsized GaN particles. The results found the only filler that induce ultralow wear is the GaN fiber which was microns in size and friable under shear stresses. This study reinforces the leading hypothesis that a mechanistic synergy is required for ultralow wear PTFE composites. • Gallium nitride fibers reinforced PTFE wear rates are over three orders of magnitude lower than unfilled PTFE. • Low wear behavior derived from nanostructured gallium nitride fibers and tribochemically altered PTFE. • Environmental tribology tests and molecular simulations were used for the mechanistic study. • A synergistic anti-wear mechanism of mechanics and tribochemistry was proposed. [ABSTRACT FROM AUTHOR]