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Author: Börner, Martin × DDC: 540 ×

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    Deposition of exchange-coupled dinickel complexes on gold substrates utilizing ambidentate mercapto-carboxylato ligands
    (Frankfurt, M. : Beilstein-Institut zur Förderung der Chemischen Wissenschaften, 2017) Börner, Martin; Blömer, Laura; Kischel, Marcus; Richter, Peter; Salvan, Georgeta; Zahn, Dietrich R. T.; Siles, Pablo F.; Fuentes, Maria E. N.; Bufon, Carlos C. B.; Grimm, Daniel; Schmidt, Oliver G.; Breite, Daniel; Abel, Bernd; Kersting, Berthold
    The chemisorption of magnetically bistable transition metal complexes on planar surfaces has recently attracted increased scientific interest due to its potential application in various fields, including molecular spintronics. In this work, the synthesis of mixed-ligand complexes of the type [NiII2L(L’)](ClO4), where L represents a 24-membered macrocyclic hexaazadithiophenolate ligand and L’ is a ω-mercapto-carboxylato ligand (L’ = HS(CH2)5CO2− (6), HS(CH2)10CO2− (7), or HS(C6H4)2CO2− (8)), and their ability to adsorb on gold surfaces is reported. Besides elemental analysis, IR spectroscopy, electrospray ionization mass spectrometry (ESIMS), UV–vis spectroscopy, and X-ray crystallography (for 6 and 7), the compounds were also studied by temperature-dependent magnetic susceptibility measurements (for 7 and 8) and (broken symmetry) density functional theory (DFT) calculations. An S = 2 ground state is demonstrated by temperature-dependent susceptibility and magnetization measurements, achieved by ferromagnetic coupling between the spins of the Ni(II) ions in 7 (J = +22.3 cm−1) and 8 (J = +20.8 cm−1; H = −2JS1S2). The reactivity of complexes 6–8 is reminiscent of that of pure thiolato ligands, which readily chemisorb on Au surfaces as verified by contact angle, atomic force microscopy (AFM) and spectroscopic ellipsometry measurements. The large [Ni2L] tail groups, however, prevent the packing and self-assembly of the hydrocarbon chains. The smaller film thickness of 7 is attributed to the specific coordination mode of the coligand. Results of preliminary transport measurements utilizing rolled-up devices are also reported.
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    Green-Emissive Zn2+ Complex Supported by a Macrocyclic Schiff-Base/Calix[4]arene-Ligand: Crystallographic and Spectroscopic Characterization
    (Weinheim : Wiley-VCH, 2021) Ullmann, Steve; Börner, Martin; Kahnt, Axel; Abel, Bernd; Kersting, Berthold
    The macrocyclic calix[4]arene ligand H2L comprises two non-fluorescent 2,6-bis-(iminomethyl)phenolate chromophores, which show a chelation-enhanced fluorescence enhancement upon Zn2+ ion complexation. Macrocyclic [ZnL] complexes aggregate in the absence of external coligands via intermolecular Zn−N bonds to give dimeric [ZnL]2 structures comprising two five-coordinated Zn2+ ions. The absorption and emission wavelengths are bathochromically shifted upon going from the liquid (λmax,abs (CH2Cl2)=404 nm, λmax,em (CH2Cl2)=484 nm) to the solid state (λmax,abs=424 nm (4 wt%, BaSO4 pellet), λmax,em=524 nm (neat solid)). Insights into the electronic nature of the UV-vis transitions were obtained with time-dependent density functional theory (TD-DFT) calculations for a truncated model complex.