The structures and reactivity of various catalytic model systems of nitrogenase are reviewed. Firstly, the Schrock cycle is discussed as an example of a nitrogen-fixing system for which the mechanism has been elucidated both experimentally and theoretically. Then a series of mononuclear iron complexes based on tetradentate ligands of the type EP 3 (E = Si, C, B) is discussed. These systems both serve as highly active catalysts for the synthesis of ammonia from N 2 and provide important insights into the role of the ligand situated in the position trans to coordinated N 2 . In addition, new cobalt, iron, ruthenium, and osmium complexes that display catalytic conversion of N 2 into [a] 1337 Felix Tuczek studied chemistry at Johannes-Gutenberg University Mainz and received his PhD in 1989 in the group of Philipp Gütlich for work in Mössbauer emission spectroscopy. After two years as a postdoc at Stanford University in the group of Prof. Ed Solomon he returned to Mainz to work on his habilitation (1997) on copper peroxo and azido complexes with relevance to hemocyanin. In 1999 he received a call to Christian Albrechts University Kiel and since then has been professor of molecular inorganic chemistry in Kiel. His scientific interests include nitrogen fixation, type 3 copper proteins, and corresponding small-molecule model systems, as well as molecular switches. Nadja Stucke studied chemistry at Christian Albrechts University of Kiel and received her master's degree in 2014. Since 2014 she has been a PhD student in the working group of Prof. Dr. F. Tuczek. Her scientific interests are focused on synthetic nitrogen fixation. Benedikt Flöser studied chemistry at Christian Albrechts University of Kiel, received his master's degree in 2014, and proceeded to work as a PhD student in the group of Prof. Dr. F. Tuczek. His research is concerned with quantum chemistry in small molecule activation (N 2 fixation, oxygen activation), and spin crossover systems. Thomas Weyrich studied chemistry at Christian Albrechts University of Kiel, where he obtained his master's degree in 2013 after completion of his thesis dealing with synthetic nitrogen fixation under the supervision of Prof. Dr. Felix Tuczek. He continued his research in this field for his PhD thesis by synthesizing new phosphine ligands for molybdenum-based dinitrogen fixation.

Two new dihydroxybenzoquinone-based metal-organic frameworks, ((CH3)2NH2)3[Al4(L1)3(L1(•))3]·3DMF (1, denoted CAU-20) and ((CH3)2NH2)3[Al4(L2)3(L2(•))3]·9DMF (2, denoted CAU-20-Cl2), were synthesized at 120 °C in DMF using 2,5-dihydroxy-p-benzoquinone ((C6H2(OH)2(O)2), H2L1) and 2,5-dichloro-3,6-dihydroxy-p-benzoquinone ((C6Cl2(OH)2(O)2), H2L2), respectively. Compared to other Al-MOFs, which contain carboxylate or phosphonate groups that connect the metal sites, in 1 and 2 the Al(3+) are coordinated by oxido groups. The metal ions are octahedrally surrounded by oxygen atoms of the deprotonated linker molecules to generate honeycomb layers with a metal to linker ratio of Al: L1/L2 = 2:3. The layers contain L1(2-) and L2(2-) ions as well as linker radical ions L1(•3-) and L2(•3-) in a molar ratio of 1 to 1. The presence of radical ions was confirmed by EPR and UV-vis-spectroscopic measurements, and the composition was determined from a combination of PXRD, (1)H NMR, TG, and elemental analyses. Charge balance is accomplished through intercalation of (CH3)2NH2(+) ions which are formed by partial hydrolysis of DMF. In the structures of 1 and 2 the eclipsed layers are AA and ABAB stacked, respectively, and one-dimensional hexagonal channels with diameters of ca. 9 and 6 Å are formed. Both compounds exhibit permanent porosity and have specific surface areas of 1440 and 1430 m(2) g(-1), respectively.

The host–guest complex formation between barbital and various acylaminopyridyl isophthalamides (Hamilton receptors) has been determined quantitatively. The syntheses of nine isophthalamides are described. Their structures differ in the substitution patterns on the central isophthalic unit, and the natures of the acyl residues. Ethylhexanoyl derivatives proved to be more soluble than pentanoyl amides. The association constants were determined by 1H NMR titrations monitoring chemically induced shifts (CIS values), by 1H NMR diffusion experiments, and by isothermal titration calorimetry (ITC), giving Kass values in chloroform at 298 K between 33 × 103 and 100 × 103 M–1.

A new redox active MOF Al-MIL-53-FcDC based on 1,1′-ferrocenedicarboxylate exhibits reversible electrochemical activity and permanent porosity.

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