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The displacement processes of several guests, incorporated in a calixarene host system, were investigated in the gas phase by electrospray ionization-Fourier transform-ion cyclotron resonance (ESI-FT-ICR) mass spectrometry. The complexes resulting from a resorcin[4]arene host with ammonia and sec-butylamine guests were isolated in an ICR-cell, separately using both states of the photos-witch as well as two reference systems for the open and closed forms of the photoswitchable host. The isolated complexes were forced to exchange the guest by using methylamine, ethylamine and sec-butylamine, resulting in different reaction rates for all the measured systems. Especially, the reaction rates of both states of the photoswitch are dependent on the provided guest. Potential side effects like proton exchanges were examined by an H/D-exchange experiment. The results were investigated and supported by quantum chemical calculations (DFT). Copyright (C) 2008 John Wiley & Sons, Ltd.

We synthesized the new supramolecular host molecules 7 and 13 based on functionalized resorcarenes bearing Kemp's triacid. Conformations in solution have been investigated and the influence of intra-and intermolecular hydrogen bonds from the triacid was shown by low temperature and DOSY NMR experiments. The results of host 7 are supported by DFT calculations. The binding behaviour of 7 towards different 2-amino pyridincs in chloroform has been investigated by NMR titrations. The association constants reach from K 207 M-1 for 2-amino-5-cyano pyridine to K=1551 M-1 for 2-amino-4-methyl pyridine. The association constants of the formed complexes of 7 with 2-amino pyridines were compared with those of the simple host systems 14 and 15 in order to evaluate the influence of the attached resorcarene host. (c) 2008 Elsevier Ltd. All rights reserved.

The synthesis of calix[4]arenes bearing two quinazolin-4-ones group at the upper rim is decribed. H-1 NMR spectra and quantum chemical calculations make it possible to suggest that calix[4]arenequinazolinones form three rotamers in solutions at room temperature, due to the restricted rotation of the quinazolinone fragments. The X-ray structure investigation indicates that quinazolin-4-onecalix[4]arene exists in the crystal state as the methanol 1: 1 inclusion complex. (C) 2007 Elsevier Ltd. All rights reserved.

Host-guest complexes of tetramethylcavitand with different ammonium cations were investigated by using a quantum chemical method at the density func tional level (BP86, B3LYP). The NH4+ cation is strongly bound to the host. Increasing creasing methyl substitution at the cation decreases its inclination towards the complex formation. The calculated data are in line with results from electrospray ionization mass spectrometry (ESI-MS) experiments. They reveal stable aggregates only for the NH4+ cation and for the primary alkylammonium cations.

Treatment of 4-fluoro-5-(1,1,2,2-tetrafluoroethyl)-3H-1,2-dithiole-3-thione with 2 equivalents of sodium sulfide gives after acidification 3,4-difluoro-2-mercapto-1,6,6a gimel(4)-trithiapentalene, which can be further reduced by sodium sulfide to 3,5-difluoro-4-mercapto-thiopyran-2-thione. (c) 2006 Elsevier B.V. All rights reserved.

Recently a new type of calix[4]arenes has been synthesized via condensation of 2,6-dihydroxypyridine and a number of aldehydes. This type of pyridine[4]arenes forms capsules consisting of two single pyridine[4]arenes. These capsules can incorporate different guest molecules, like carboxylic acids and amides in this case. We proved that the guest acids really are incorporated inside the cavity of the capsules by electrospray mass spectrometry, NMR spectroscopy, and theoretical calculations.

The conjugation effects in iminophosphines H3C-N = P-R (R = H, Hlg, OH, NH2, PH2, SiH3, SH) and heterobutadienes H3C-N = P-X = CY2 (X = N, P; Y = NH2, H) and their manifestations in NMR spectra are analyzed by RHF and MP2 calculations using the 6-31+G and 6-311+G basis sets with different numbers of polarization functions. The contribution of π-mesomeric interactions to the electronic structure of these compounds is estimated from the theoretical and experimental structural parameters, calculated natural atomic charges and bond indices, surfaces of rotational coordinates of the potential energy, and energy balances of isodesmic reactions, and also from the experimental and theoretically calculated (GIAO) 15N and 31P NMR chemical shifts. The configuration of model heterobutadienes relative to the P = N double bond and the trans conformation of the N = P-X = C fragment, suggested by the calculation results, are consistent with the structural data for the compounds Mes*-N = P-X = C(NR2)2 (X = N, P; R = Alk). The character of π-meso-meric interactions in the examined series of iminophosphines and butadienes derived from them is discussed. The conjugation effects influence the stability of phosphabutadienes insignificantly.

A broad range of (phosphino)(aryl)carbenes, 1b-d, 10a,b, and 14a,b, were prepared by photolysis of their diazo precursors. The influence of the steric and electronic properties of the aryl ring on the structure and stability of these carbenes was studied both experimentally and theoretically. Among the different stabilization modes investigated, those featuring an acceptor as well as a spectator aryl substituent result in stable or at least persistent carbenes that could be completely characterized by classical spectroscopic methods. In marked contrast, the new substitution pattern featuring a donor aryl ring results in a very fleeting carbene.

The substituent effects on the singlet-triplet energy separations are explored for phosphanylnitrenes and related congeners from the Group 14 to Group 16 elements. Imine-type substituents (e.g, phosphaniminato, methyleneimine etc.) are more effective than amino groups in lowering the energy of a singlet below that of a triplet state. It is due to an effective stabilisation of the singlet and a destabilisation of the triplet.

The formation of coordination compounds of phosphanyl carbenes with a transition metal in a high oxidation state (Schrock type) is evaluated by density functional theory. In the Schrock type carbene complexes the transition metal-carbon bond possesses a multiple bond character. If one of the ligands at the carbene center possesses a leaving ability, e.g. as the diaminophosphenium unit, a facile distortion to a new type of an anionic metallaalkylidene donor-acceptor complex with a diaminophosphenium cation is predicted. (C) 2001 Elsevier Science B.V. All rights reserved.

The formation of a Fischer-type transition metal complex with a W(CO)(5) fragment is evaluated for the phosphanylcarbenes, Arduengo-type carbenes, and Bertrand-type carbenes by means of quantum chemical investigations at a density functional level with effective core potential methods. Accordingly, the stabilities of the complexes depend strongly on the substitution pattern of the carbenic unit. Amino-substituted carbenes as well as the Arduengo-type carbene form stable transition metal complexes. The stabilities of the complexes decrease for the phosphanylcarbenes and are at a minimum for the hitherto unknown transition metal complexes of the push-pull-type carbene of Bertrand. The matter is analyzed in terms of distortion energies required to bring the carbene units into the geometrical standard state for complexation with the transition metal fragment. The arguments evaluated for the phosphanylcarbenes should hold equally well for other carbenes substituted with electropositive ligands. For the mono-phosphanylcarbenes, eta (1) as well as eta (2) structures are investigated. For the diphosphanylcarbenes, a new structural type of metal complexes is predicted in which the transition metal fragment is strongly bound to a cyclic structural valence isomer of the carbene.

The P-31 NMR spectra of the iminophosphines R2N-P=NMes* [R = Me (2a), Et (2b), i-Pr (2c); Mes* = 2,4,6-tri-tert-butylphenyl] were studied in the solid state under magic angle spinning conditions and in solution. Evaluation of the solid-state data in connection with CIAO quantum chemical model calculations allows the characterization of the P-31 nuclear magnetic shielding tensors and leads to assignment of Z-configuration for the double bond in 2a and of the E-configuration for the double bonds in 2b and c. Comparison of the shifts delta(iso) with the chemical shift in solution (delta(soln)) indicates that this configuration is retained in solution only for 2c, whereas solutions of 2a and b contain rapidly exchanging equilibrium mixtures of both E- and Z-isomers. The analysis of the temperature dependence of delta(soln) allows for the first rime the evaluation of Delta H and Delta S for this isomerization. The results reveal that in the case of 2b the configuration of the more stable stereoisomer is opposite to the conformation observed in the solid state. Copyright (C) 2000 John Wiley & Sons, Ltd.

Quantum chemical calculations at the ab initio level indicate that Lewis donors such as amine or water form weak donor-acceptor complexes with fluoro-substituted silanes. The strength of the donor-acceptor formation increases with increasing degree of fluorine substitution. Amine and water form strong adducts only for tetrafluorosilane. The higher element homologues of Lewis donors, such as phosphane and sulfur dihydride, do not in essence coordinate. A considerable role in donor-acceptor formation is exerted by chelation effects which impose intramolecular interactions on functionalized ligands. The corresponding structures are explored.

1,1-Dichloropolyfluoropentylsulfenyl chlorides react with lithium hexamethyldisilylamide with the formation of N,N -bis(trimethylsilyl)- 1-chloro-polyfluoropentyl-1-en-sulfenamide.

A wide series of low-coordinated phosphorus (III) compounds including iminophosphines 1, two- 2 or mono-coordinated 3 phosphorus-containing cations, and anion 4, where Mes∗ = 2,4,6-tris-(tert-butyl)phenyl, has been investigated by 13C, 15N and 31P NMR spectroscopy. The spectral parameters obtained are considered in connection with the ab initio (6–31G∗) calculation data of the model compounds.

The reactions of phosphenium salts (Cl–P+–NR2)A–(A = AlCl4, CF3SQ3)1 with guanidines (R2N)2CNSiMe32 afford dicationic 1,3-bis[bis(dialkylamino)methylene]-1,3-diazonia-2λ3, 4λ3-diphosphacyclobutanes 3 or 1,3-bis[bis(dialkylamino)methylene]-1,3-diazonia-2λ3-phospha-4,4,4-trichloroaluminacyclobutanes 5, depending on the experimental conditions.

Several recent developments in our laboratories have made it possible to elaborate a general method for preparing optically pure fluorine containing α-amino acids starting from a Ni(II)-complex ( 1 ) of a Schiff's base derived from (S)-o-[(benzylpropyl)amino]-benzophenone (BBP) and glycine or alanine. Alkylation of ( 1 ) with fluorine-substituted benzyl halides and aldehyde condensation result, respectively, in fluorine-containing S-Phe and its α-methyl derivatives, 2R,3S-, 2S,3R-, 2R,3R-PhSer and 2S,3S-β-perfluoroalkyl Ser in good chemical and optical yields. Simplicity of the synthetic procedure, ease of recovery of the chiral auxiliary (BBP), and the possibility of obtaining optically pure fluorine containing amino acids make this method attractive. The influence of fluorine atoms or fluorine containing groups and reaction conditions on the stereochemical results in the reactions of this type will be discussed.

Alkylation of trans-N-alkyl(or aryl)-N'-(3-hydroxy-1,1-dioxothiolan-4-yl) thioureas with ethyl p-toluenesulfonate, and the reaction of cyanogen bromide wiht an ethyl p-toluenesulfonate, and the reaction of cyanogen bromide with trans-3-hydroxy-4-aminothiolan-1,1-dioxides have given salts of trans-2-iminoperhydrothieno[3,4-d]-oxazole 5,5-dioxides. Rearrangement of these oxazolidines in the presence of bases afford perhydrothieno[3,4-d]imidazole-2-one 5,5-dioxides.

Reaction of trans-3-chloro-A-aminothiolane 1,1-dioxide hydrochloride with aryl isothiocyanates gives, according to the base involved, cis-perhydrothieno[3,4-d]imidazole-2-thione 5,5-dioxides or the hitherto undescribed cis-2-aryliminoperhydrothieno 3,4-d] thiazole 5,5-dioxides.

Examination of the PMR spectra of eleven bicyclic thiolane 1,1-dioxide derivatives has enabled those features of the spectral parameters characteristic of the cis- and trans-orientation of the two condensed five-membered heterocycles to be established. The proton coupling constants show that the conformation of the 1,1-dioxothiolane ring in both types of compound in solution differs from that in the crystalline state, as determined by x-ray analysis.

The mono- and bidentate chelation of the main-group elements silicon, germanium, tin, and lead through the phosphorus atoms of the diphosphanylmethanide ligand has been studied by means of quantum chemical methods. In accord with experimental investigations, the species are found to adopt a psi-tbp conformation of high flexibility. The various distortional modes causing the axial and equatorial positions to become equivalent have also been investigated. In addition, the bonding situations in the electronically related bis(diamino)- and the higher element homologue bis(diarsanyl)methanide ligand systems have been studied. The bonding situation in the hitherto experimentally unknown bis(diamino)methanide Ligands is predicted to be similar to that in bis(amidinate) complexes. An analysis of the electron distributions (natural bond orbital population analysis) in these compounds reveals that the central main-group element is positively charged and weakly chelated by the surrounding ligands.

Recently, an unusual elongation of the C-S bond was observed experimentally for some sulfur-containing heterocycles. Using a superior ab initio (SCS-MP2/cc-pVTZ) level of theory, we showed that the phenomenon can be explained by a contribution of a donor–acceptor adduct of a carbene with an unsaturated ligand. One may achieve further elongation of the C-S bond, eventually turning it to a coordinate one, by increasing the stability of each part of the system as, e.g., in the utmost case of spiro adducts with Arduengo carbenes. The effect of carbene stability was quantified by employing the isodesmic reactions of carbene exchange.

Anopheles darlingi is the main vector of malaria in Brazil, characterized by a high level of anthropophilia and endophagy. Imidacloprid, thiacloprid, and acetamiprid are the most widespread insecticides of the neonicotinoid group. However, they produce adverse effects on the non-target insects. Flupyradifurone has been marketed as an alternative to non-fluorinated neonicotinoids. Neonicotinoids containing trifluoroacethyl substituent reveal increased insecticidal activity due to higher hydrophobicity and metabolic stability. We synthesized novel neonicotinoid insecticides containing fluorinated acceptor groups and their interactions were estimated with the nicotinic acetylcholine receptor (nAChR) binding site by molecular docking studies, to evaluate their larvicidal activity against A. darlingi, and to assess their outdoor photodegradation behavior. New neonicotinoid analogues were prepared and characterized by NMR and mass-spectrometry. The synthesized molecules were modelled by time-dependent density functional theory and analyzed, their interaction with nAChR was investigated by molecular docking. Their insecticide activity was tested on Anopheles larvae collected in suburban area of Manaus, Brazil. Four new fluorinated neonicotinoid analogs were prepared and tested against 3rd instars larvae of A. darlingi showing high larvicidal activity. Docking studies reveal binding modes of the synthesized compounds and suggest that their insecticidal potency is governed by specific interactions with the receptor binding site and enhanced lipophilicity. 2-Chloro-5-(2-trifluoromethyl-pyrrolidin-1-ylmethyl)pyridine 5 showed fast degradation in water maintaining high larvicidal activity. All obtained substances possessed high larvicidal activity in low concentrations in 48 hours of exposure, compared to commercial flupyradifurone. Such activity is connected to a unique binding pattern of the synthesized compounds to insect's nAChR and to their enhanced bioavailability owing to introduction of fluorinated amino-moieties. Therefore, the compounds in question have a high potential for application as control agents for insects transmitting tropical diseases, and they will be less persistent in the environment. © 2020 da Silva Mesquita et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.