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Theinteractions between halogen-substituted s-trazine(C3H2N3X) and halide anions(Y–) have been investigated at the MP2/aug-cc-pVDZ(aug-cc-pVDZ-PP) level. C3H2N3X caninteract with halide anions to form five types of complexes (C3H2N3X·Y–): astrong σ-type interaction complex, a weak σ-type interactioncomplex, an anion−π interaction complex, a hydrogen-bondingcomplex, and a halogen-bonding complex. The binding energies, structures,and bonding characteristics of these complexes have been discussed.The local details of potential energy surfaces around the bindingsites for some selected complexes have been depicted. The resultsindicate that the binding behavior of F–is quitedifferent from that of Cl–, Br–, and I–. The potential energy surface is separatedinto two parts, the HB-σ–π region and the XB region,by a relatively high energy barrier for complexes C3H2N3Cl·Cl–, C3H2N3Br·Cl–, and C3H2N3I·Cl–. The HB-σ–πregion is characterized by the flat potential energy surface, indicatingthat the binding strength is retained when the anion is held overthe HB-σ–π region. The XB region is characterizedby the steeper potential energy surface, indicating that the bindingstrength is more sensitive to the anion position in this region. Thebinding strength of the HB-σ–π region is strongerthan that of the XB region for C3H2N3Cl·Cl–and C3H2N3Br·Cl–, whereas the binding strengthof the XB region is stronger than that of the HB-σ–πregion for C3H2N3I·Cl–. [ABSTRACT FROM AUTHOR]

The intermolecular interactions between the heavy alkenes H 2 Si=TH 2 (T = C, Si, Ge, Sn, Pb) and H 2 O or HCl have been explored at the CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVDZ level. The various hydrogen bond (HB) and tetrel bond (TB) complexes can be located on the basis of molecular electrostatic potential maps of the isolated monomers. The competition between TB and HB interactions has been investigated through the relaxed potential energy surface scan. The results indicate that the HB complexes become more and more unstable relative to the TB complexes with the increase of the T atomic number, and cannot even retain as a minimum in some cases, for H 2 Si=TH2···H 2 O systems. In contrast, the HB complexes are generally more stable than TB complexes, and the TB complexes exhibit rather weak binding strength, for H 2 Si=TH 2 ···HCl systems. The majority of the TB complexes formed between H 2 Si=TH 2 and H 2 O possesses very strong binding strength with covalent characteristics. The noncovalent TB complexes can be divided into two types on the basis of the orbital interactions: π-hole complexes, with binding angles ranging from 91 to 111°, and hybrid σ/π-hole complexes, with binding angles ranging from 130 to 165°. The interplay between different molecular interactions has been explored, and an interesting result is that the covalent TB interaction is significantly abated and becomes noncovalent because of the competitive effect., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

The natural flavonoid fisetin (3,3',4',7-tetrahydroxyflavone) was discovered to possess antitumor activity, revealing its potential value in future chemotherapy. However, its poor water solubility makes it difficult for intravenous administration. In this study, the monomethyl poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) copolymer was applied to prepare nanoassemblies of fisetin by a self-assembly procedure. The prepared fisetin micelles gained a mean particle size of 22 ± 3 nm, polydisperse index of 0.163 ± 0.032, drug loading of 9.88 ± 0.14%, and encapsulation efficiency of 98.53 ± 0.02%. Compared with free fisetin, fisetin micelles demonstrated a sustained and prolonged in vitro release behavior, as well as enhanced cytotoxicity, cellular uptake, and fisetin-induced apoptosis in CT26 cells. As for in vivo studies, fisetin micelles were more competent for suppressing tumor growth and prolonging survival time than free fisetin in the subcutaneous CT26 tumor model. Furthermore, histological analysis, terminal deoxynucleotidyl transferase-mediated nick-end labeling assay, immunohistochemical detection of Ki-67, and microvessel density detection were conducted, demonstrating that fisetin micelles gained increased tumor apoptosis induction, proliferation suppression, and antiangiogenesis activities. In conclusion, we have successfully produced a MPEG-PCL-based nanocarrier encapsulating fisetin with enhanced antitumor activity.