Intermolecular interactions between σ- and π-holes of bromopentafluorobenzene and pyridine: computational and experimental investigations.

The characters of σ- and π-holes of bromopentafluorobenzene (C6F5Br) enable it to interact with an electron-rich atom or group like pyridine which possesses an electron lone-pair N atom and a π ring. Theoretical studies of intermolecular interactions between C6F5Br and C5H5N have been carried out at the M06-2X/aug-cc-pVDZ level without and with the counterpoise method, together with single point calculations at M06-2X/TZVP, wB97-XD/aug-cc-pVDZ and CCSD(T)/aug-cc-pVDZ levels. The σ- and π-holes of C6F5Br exhibiting positive electrostatic potentials make these sites favorably interact with the N atom and the π ring of C5H5N with negative electrostatic potentials, leading to five different dimers connected by a σ-holen bond, a σ-holeπ bond or a π-holeπ bond. Their geometrical structures, characteristics, nature and spectroscopy behaviors were systematically investigated. EDA analyses reveal that the driving forces in these dimers are different. NCI, QTAIM and NBO analyses confirm the existence of intermolecular interactions formed via σ- and π-holes of C6F5Br and the N atom and the π ring of C5H5N. The experimental IR and Raman spectra gave us important information about the formation of molecular complexes between C6F5Br and C5H5N. We expect that the results could provide valuable insights into the investigation of intermolecular interactions involving σ- and π-holes.

1,2-Bis{2-[(1,3-benzothia-zol-2-yl)sulfanylmeth-yl]phen-oxy}ethane.

The mol-ecule of the title compound, C(30)H(24)N(2)O(2)S(4), adopts a Z-shaped conformation. The terminal benzothia-zole ring systems are oriented at a dihedral angle of 60.81 (8)°, while the central benzene rings are twisted to each other by a dihedral angle of 13.56 (14)°. Weak inter-molecular C-H⋯π inter-actions are present in the crystal structure.

Bis{µ-4'-[4-(quinolin-8-yloxymeth-yl)phen-yl]-2,2':6',2''-terpyridine}disilver(I) bis-(perchlorate) dimethyl-formamide disolvate.

In the binuclear title complex, [Ag(2)(C(31)H(22)N(4)O)(2)](ClO(4))(2)·2C(3)H(7)NO, the Ag(I) atom is penta-coordinated by three N atoms from the tridentate chelating terpyridyl group and by one N atom and one O atom from the quinolin-8-yl-oxy group in a distorted square-pyramidal geometry with the O atom at the apical position. The centrosymmetric complex cation involves intra-molecular π-π stacking inter-actions [centroid-centroid distance = 3.862 (4) Å] between the central pyridine and benzene rings. In the crystal structure, inter-molecular C-H⋯O hydrogen bonds result in the formation of a supra-molecular network.

Dictyoptesterols A-C, ∆22-24-oxo cholestane-type sterols with potent PTP1B inhibitory activity from the brown alga Dictyopteris undulata Holmes.

Three new cholestane-type sterols bearing an unusual ∆22-24-oxo side chain, namely, dictyoptesterols A-C (1-3), were isolated from the brown alga Dictyopteris undulata Holmes, together with five known strutural analogues (4-8). Their structures were elucidated on the basis of by extensive spectroscopic analysis. The absolute configurations of the steroidal nuclei of the new compounds were proposed by a comparison of NMR data with those of related known compounds as well as biogenetic considerations. All of the isolates were evaluated in vitro for their potential to inhibit protein tyrosine phosphatase-1B (PTP1B) activity. The results showed that compounds 1-5 exhibited different levels of PTP1B inhibitory activities with IC50 values ranging from 3.03 ±â€¯0.76 to 15.01 ±â€¯2.88 µM. In particular, compounds 3 and 4 showed promising inhibitory effects towards PTP1B with IC50 values of 3.03 ±â€¯0.76 and 3.72 ±â€¯0.40 µM, respectively, when compared to the positive control oleanolic acid (IC50, 2.83 ±â€¯0.39 µM). The chemotaxonomic significance of these isolated ∆22-24-oxo cholestanes has also been discussed.

Luminescent lanthanide metal-organic frameworks for chemical sensing and toxic anion detection.

Prototype lanthanide metal-organic frameworks (LnMOFs), Ln(BTC) (Ln = Eu and Tb; BTC = benzene-1,3,5-tricarboxylate), have been considered as luminescent sensors for detecting toxic anions, while their neutral pore structures have limited the entrance and encapsulation of anions to produce highly anion-responsive photoluminescence (PL). To facilitate anions to enter the pore space of Ln(BTC), a one-pot synthesis method was proposed in which BTC was partially replaced with its structural analogue L·BF4 (H3L·BF4 = 2,4,6-tricarboxy-1-methylpyridinium tetrafluoroborate) which consists of an anion affinity site of cationic methylpyridinium. Compared to the original Ln(BTC), the co-doped cationic framework Eu0.05Tb0.95-BTC0.9L0.1 is highly sensitive for detecting different toxic anions by tuning the energy absorption of organic chromophores, the energy transfer efficiency to Ln3+ ions and the energy allocation between different Ln3+ ions in the PL spectra. We demonstrated that the Eu0.05Tb0.95-BTC0.9L0.1 PL sensor has the capability of decoding various toxic anions with a clearly differentiable and unique emission intensity ratio of 5D4 → 7F5 (Tb3+, 545 nm) to 5D0 → 7F2 (Eu3+, 618 nm) transitions (ITb/IEu). Compared to Ln(BTC), the co-doped Eu0.05Tb0.95-BTC0.9L0.1 presents self-calibrating, high distinguishable and stable PL signals for detecting toxic anions.