A modular approach to the antifungal sphingofungin family: concise total synthesis of sphingofungin A and C

Sphingofungins are fungal natural products known to inhibit the biosynthesis of sphingolipids which play pivotal roles in various cell functions. Here, we report a short and flexible synthetic approach towards the sphingofungin family. Key step of the synthesis was a decarboxylative cross-coupling reaction of chiral sulfinyl imines with a functionalized tartaric acid derivative, which yielded the core motive of sphingofungins carrying four consecutive stereocenters and a terminal double bond. Subsequent metathesis reaction allowed for the introduction of different side chains of choice resulting in a total of eight sphingofungins, including for the first time sphingofungin C (eight steps from commercially available protected tartaric acid with an overall yield of 6%) and sphingofungin A (ten steps). All newly synthesized derivatives were tested for their antifungal, cell proliferative and antiparasitic activity unraveling their structure-activity relations

Novel Polypyridyl Ruthenium(II) Complexes Containing Oxalamidines as Ligands.

The complexes [Ru(bpy)2(H2TPOA)](PF6)2 ⋅ 4H2O, (1); [Ru(Me-bpy)2(H2TPOA)](PF6)2 ⋅ 2H2O, (2); [Ru(bpy)2(H2TTOA)](PF6)2 ⋅ 2H2O, (3); [Ru(Me-bpy)2(H2TTOA)](PF6)2 ⋅ 2H2O, (4) and {[Ru(bpy)2]2(TPOA)}(PF6)2 ⋅ 2H2O, (5) (where bpy is 2,2´bipyridine; Me-bpy is 4,4´- dimethyl-2,2´-bipyridine; H2TPOA is N, N´, N´´, N´´´- tetraphenyloxalamidine; H2TTOA is N, N´, N´´, N´´´- tetratolyloxalamidine) have been synthesized and characterized by 1H-NMR, FAB-MS, infrared spectroscopy and elemental analysis. The X-ray investigation shows the coordination of the still protonated oxalamidine moiety via the 1,2−diimine unit. The dimeric compound (5) could be separated in its diastereoisomers (5´) and (5´´) by repeated recrystallisation. The diastereomeric forms exhibit different 1H-NMR spectra and slightly shifted electronic spectra. Compared with the model compound [Ru(bpy)3]2+, the absorption maxima of (1)–(5) are shifted to lower energies. The mononuclear complexes show Ru(III/II)- couples at about 0.9 V vs SCE, while for the dinuclear complex two well defined metal based redox couples are observed at 0.45 and 0.65 V indicating substantial interaction between the two metal centres

Ligand‐induced donor state destabilisation – a new route to panchromatically absorbing cu(I) complexes

The intense absorption of light to covering a large part of the visible spectrum is highly desirable for solar energy conversion schemes. To this end, we have developed novel anionic bis(4 H ‐imidazolato)Cu(I) complexes (cuprates), which feature intense, panchromatic light absorption properties throughout the visible spectrum and into the NIR region with extinction coefficients up to 28,000 M −1  cm −1 . Steady‐state absorption, (spectro)electrochemical and theoretical investigations reveal low energy (Vis to NIR) metal‐to‐ligand charge‐transfer absorption bands, which are a consequence of destabilized copper‐based donor states. These high‐lying copper‐based states are induced by the σ‐donation of the chelating anionic ligands, which also feature low energy acceptor states. The optical properties are reflected in very low, copper‐based oxidation potentials and three ligand‐based reduction events. These electronic features reveal a new route to panchromatically absorbing Cu(I) complexes.Cu(I) and two chelating , anionic polymethine‐type ligands form a novel type of photoactive cuprate. The ligands induce the destabilisation of the Cu(I)‐based donor states and act themselves as acceptors. This leads to an unusually broad and intense absorption spectrum with metal‐to‐ligand charge‐transfer transitions from the visible to near‐infrared region. imag

Ruthenium(II)-bis(4'-(4-ethynylphenyl)-2,2':6', 2''-terpyridine) - A versatile synthon in supramolecular chemistry. Synthesis and characterization

A homoleptic ethynyl-substituted ruthenium(II)-bisterpyridine complex representing a versatile synthon in supramolecular chemistry was synthesized and analyzed by NMR spectroscopy, mass spectrometry and X-ray diffractometry. Furthermore, its photophysical properties were detailed by UV/Vis absorption, emission and resonance Raman spectroscopy. In order to place the results obtained in the context of the vast family of ruthenium coordination compounds, two structurally related complexes were investigated accordingly. These reference compounds bear either no or an increased chromophore in the 4̀-position. The spectroscopic investigations reveal a systematic bathochromic shift of the absorption and emission maximum upon increasing chromophore size. This bathochromic shift of the steady state spectra occurs hand in hand with increasing resonance Raman intensities upon excitation of the metal-to-ligand charge-transfer transition. The latter feature is accompanied by an increased excitation delocalization over the chromophore in the 4̀-position of the terpyridine. Thus, the results presented allow for a detailed investigation of the electronic effects of the ethynyl substituent on the metal-to-ligand charge-transfer states in the synthon for click reactions leading to coordination polymers

Photophysics of Anionic Bis(4H-imidazolato)CuI Complexes

In this paper, the photophysical behavior of four panchromatically absorbing, homoleptic bis(4H-imidazolato)CuI complexes, with a systematic variation in the electron-withdrawing properties of the imidazolate ligand, were studied by wavelength-dependent time-resolved femtosecond transient absorption spectroscopy. Excitation at 400, 480, and 630 nm populates metal-to-ligand charge transfer, intraligand charge transfer, and mixed-character singlet states. The pump wavelength-dependent transient absorption data were analyzed by a recently established 2D correlation approach. Data analysis revealed that all excitation conditions yield similar excited-state dynamics. Key to the excited-state relaxation is fast, sub-picosecond pseudo-Jahn-Teller distortion, which is accompanied by the relocalization of electron density onto a single ligand from the initially delocalized state at Franck-Condon geometry. Subsequent intersystem crossing to the triplet manifold is followed by a sub-100 ps decay to the ground state. The fast, nonradiative decay is rationalized by the low triplet-state energy as found by DFT calculations, which suggest perspective treatment at the strong coupling limit of the energy gap law

Magnetic Anisotropy and Relaxation of Pseudotetrahedral [N2O2] Bis Chelate Cobalt II Single Ion Magnets Controlled by Dihedral Twist Through Solvomorphism

The methanol solvomorph 1 amp; 8201; amp; 8901; amp; 8201;2MeOH of the cobalt II complex [Co LSal,2 amp; 8722;Ph 2] 1 with the sterically demanding Schiff base ligand 2 [1,1 amp; 8242; biphenyl] 2 ylimino methyl phenol HLSal,2 amp; 8722;Ph shows the thus far largest dihedral twist distortion between the two chelate planes compared to an ideal pseudotetrahedral arrangement. The cobalt II ion in 1 amp; 8201; amp; 8901; amp; 8201;2MeOH exhibits an easy axis anisotropy leading to a spin reversal barrier of 55.3 amp; 8197;cm amp; 8722;1, which corresponds to an increase of about 17 amp; 8201; induced by the larger dihedral twist compared to the solvent free complex 1. The magnetic relaxation for 1 amp; 8201; amp; 8901; amp; 8201;2MeOH is significantly slower compared to 1. An in depth frequency domain Fourier transform FD FT THz EPR study not only allowed the direct measurement of the magnetic transition between the two lowest Kramers doublets for the cobalt II complexes, but also revealed the presence of spin phonon coupling. Interestingly, a similar dihedral twist correlation is also observed for a second pair of cobalt II based solvomorphs, which could be benchmarked by FD FT THz EP

1,7,9,10-Tetrasubstituted PMIs Accessible through Decarboxylative Bromination: Synthesis, Characterization, Photophysical Studies, and Hydrogen Evolution Catalysis

In this work, we present a new synthetic strategy for fourfold-substituted perylene monoimides via tetrabrominated perylene monoanhydrides. X-ray diffraction analysis unveiled the intramolecular stacking orientation between the substituents and semicircular packing behavior. We observed the remarkable influence of the substituent on the longevity and nature of the excited state upon visible light excitation. In the presence of poly(dehydroalanine)-graft-poly(ethylene glycol) graft copolymers as solubilizing template, the chromophores are capable of sensitizing [Mo3S13]2− clusters in aqueous solution for stable visible light driven hydrogen evolution over three days. © 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH Gmb

Synthesis, characterization and electrochemical investigations of heterocyclic-selenocarboxylate iron complexes

cited By 2International audienceSelenocarboxylato complexes of iron containing heterocyclic group of the general formula CpFe(CO)2SeCO-het [het = 2-C4H3S (1), 2-C4H3O (2), -CH2-2-C4H3S (3)] were prepared from the reaction of iron selenide, (μ-Se)[FeCp(CO)2]2 and the corresponding heterocyclic acid chlorides. These complexes have been characterized by elemental analysis, UV-Vis, IR and 1H NMR spectroscopic techniques. The X-ray structure of 1 is determined and its electrochemical behavior has been described in details applying cyclic voltammetry. © 2016 Elsevier B.V

Tetrameres Lithium-tris(N, N-dimethylamino)silylamid: Synthese, Struktur und Reaktivität. Tetrameric Lithium Tris(N,N-dimethylamino)silylamide: Synthesis, Structure, and Reactivity

[(Me2N)3SiNHLi]4 (1) has been prepared from (Me2N)3Si—NH2 and t-BuLi. According to the crystal structure analysis 1 has a laddering structure consisting of seven four-membered rings. The two Li2(NH)2 units contain three-coordinated Li; the other five rings consist of Li(NH)2Si units in which the Li atoms are found to be four-coordinated. Reaction with bis(4-tolyl)-oxalic imidoyl chloride results in the formation of bis(N, N′-dimethylamino)-bis(4-tolyl)oxalamidine and two new heterocycles

Nickel(I)-Komplexe mit 1,1′-Bis(phosphino)ferrocenen als Liganden

Nickel(I) Complexes with 1,1′-Bis(phosphino)ferrocenes as Ligands. The thermically stable monomeric Nickel(I) complexes [(dtbpf)Ni(acac)] (1) and [(dippf)NiCl] (2) were synthesized and characterized by elemental analyses, EPR spectroscopy, and by X-ray crystal structure analyses of single crystals (dtbpf: 1,1′-bis(di-tertbutylphosphino)ferrocene; dippf: 1,1′-bis(diisopropylphosphino)ferrocene). 1 is formed by reduction of Ni(acac)2 with triethylaluminium in the presence of dtbpf, together with the nickel(0) complex [(dtbpf)Ni(C2H4)]. 1 contains a NiI atom surrounded of two O- and two P donor atoms in a distorted tetrahedral coordination. 2 was obtained by reduction of [(dippf)NiCl2] with NaBH4. In 2 the nickel(I) atom adopts trigonal planar coordination