A Metal-Capped Conjugated Polyyne Threaded through a Phenanthroline-Based Macrocycle. Probing beyond the Mechanical Bond to Interactions in Interlocked Molecular Architectures

DFT calculations with long-range
dispersion corrections have been
used to analyze the structures and binding energies of rotaxanes featuring
dimetal polyynediyl Pt2Cn dumbbells
threaded through a 1,10-phenanthroline-based macrocycle. Results indicate
that (i) the threading of the organometallic wire hardly affects its
geometric and electronic properties and (ii) the noncovalent binding
energies between the axle and macrocycle not only arise from mechanical
bonding enforced weak interactions derived from the close proximity
of the sp carbon chain to the macrocycle atoms, but also include hydrogen-bonding
contacts involving hydrogen atoms of the metal bound phosphine ligands
of the former and the nitrogen and oxygen atoms of the latter. The
optimized geometries of the rotaxane and macrocycle are compared to
the corresponding crystal structures where available.