Hydrogen-bond-induced selectivity of a head-to-head photo-dimerisation of dialkynylanthracene - access to tetradentate Lewis acids.

Using 2-hydroxypropyl-protecting groups, 1,8-dialkynylanthracene photo-dimers were prepared in head-to-head-configuration by UV irradiation on a multi-gram scale. In non-polar solvents, the combination of non-covalent hydrogen bonds and π-π-interactions induces the formation of the -isomer in up to 85% yield. Instead, more polar solvents or irradiation of unprotected 1,8-diethynylanthracene led to formation of the corresponding -isomer in large excess.

A Rational Approach to Tetra-Functional Photo-Switches.

α,ω-Bis(1,8-dichloroanthracen-10-yl)alkanes with (CH) -linker units (=1-4) were synthesized starting from 1,8-dichloroanthracen-10(9)-one. This was transformed into anthracenes with allyl, bromomethyl and propargyl substituents in position 10; these were converted in various C-C-bond formation reactions (plus hydrogenation), leading to two anthracene units flexibly linked by α,ω-alkandiyl groups. 1,2-Ethandiyl- and 1,3-propandiyl-linked derivatives were functionalized with ethynyl groups in positions 1, 8, 1' and 8', and these terminally functionalized by MeSn groups using MeNSnMe.

Aurophilicity in action: stepwise formation of dinuclear Au(i) macrocycles with rigid 1,8-dialkynylanthracenes.

Two phosphane-gold(i) functions (with tri(para-tolyl)- or tri-n-butylphosphane) were attached to a 1,8-diethynylanthracene backbone. The ligand size prevents direct interaction between the gold atoms, but the initial products rearrange to form macrocyclic anions comprising two 1,8-diethynylanthracene and two gold units, linked to cationic gold(i) fragments by maximising aurophilic interactions.

Bidentate Boron Lewis Acids: Selectivity in Host-Guest Complex Formation.

Bidentate boron Lewis acids based on 1,8-diethynylanthracene were synthesised in two steps by initial stannylation of the terminal alkynes and subsequent tin-boron exchange with different chloroboranes. The reactions were very selective, and the target compounds were obtained in high purity and good to excellent yields. Complexation experiments of 1,8-bis[(diphenylboranyl)ethynyl]anthracene with nitrogen bases (pyridine, pyrimidine, TMEDA) afforded three stable adducts, which were structurally characterised by X-ray diffraction.

Mechanism of host-guest complex formation and identification of intermediates through NMR titration and diffusion NMR spectroscopy.

The formation of host-guest (H-G) complexes between 1,8-bis[(diethylgallanyl)ethynyl]anthracene (H) and the N-heterocycles pyridine and pyrimidine (G) was studied in solution using a combination of NMR titration and diffusion NMR experiments. For the latter, diffusion coefficients of potential host-guest structures in solution were compared with those of tailor-made reference compounds of similar shape (synthesized and characterized by NMR, HRMS, and in part XRD). Highly dynamic behavior was observed in both cases, but with different host-guest species and equilibria.