The interaction of appropriate metal ions (Pb(II), Zn(II)) with helical ligand strands, obtained by hydrazone polycondensation, generates polymetallic supramolecular architectures of rack and grid types, by uncoiling of the ligand. The interconversion between the helical free ligand and the linearly extended ligand in the complexes produces reversible ion-induced, nanomechanical molecular motions of large amplitude. It has been integrated in an acid-base neutralisation fuelled process, which links the extension/contraction of the ligand strands to alternating changes in pH.

Formation of RACK- and grid-type metallosupramolecular architectures and generation of molecular motion by reversible uncoiling of helical ligand strands.

Stereochemistry and reaction rates of anionopentaamine complexes of cobalt(III) and chromium(III)

Reaction of a bent py-hyz-pym-hyz-pym 1 and of a linear py-hyz-py-hyz-pym 3 (py=pyridine; pym=pyrimidine; hyz=hydrazone) ligand strands with silver(I) tetrafluoroborate in CH3NO2 generates double-helical dinuclear 2 and trinuclear 4 complexes. These complexes form polymeric, highly ordered solid-state structures, with wirelike, linear continuous or discontinuous polycationic Agn+ arrays with AgAg distances of 2.78 to 4.42 A. Ligand 5, an isomer of 1, is found to yield a [2×2] grid-type complex 6. Titration experiments reveal the formation of linear rack-type dinuclear species from 1 and 5. Acid–base modulated, reversible interconversion between strand 1 and double helicate 2 may be achieved by using tren as a competing complexing agent (tren=N(CH2CH2NH2)3). Progressive addition of silver(I) ions to a 1:1 mixture of 1 and 5 leads to the preferential formation of the double helicate 2 over the grid complex 6, illustrating a process of self-organisation with selection of the correct ligand.

https://chemistry-europe.onlinelibrary.wiley.com/doi/pdf/10.1002/chem.200600726

Solid‐State Self‐Assembly of Polymeric Double Helicates Leading to Linear Arrays of Silver(I) Ions and Reversible Strand/Double Helix Interconversion in Solution

General design principles have been developed for the control of the structural features of polyheterocyclic strands and their effector-modulated shape changes. Induced defined molecular motions permit designed enforcement of helical as well as linear molecular shapes. The ability of such molecular strands to bind metal cations allows the generation of coiling/uncoiling processes between helically folded and extended linear states. Large molecular motions are produced on coordination of metal ions, which may be made reversible by competition with an ancillary complexing agent and fueled by sequential acid/base neutralization energy. The introduction of hydrazone units into the strands confers upon them constitutional dynamics, whereby interconversion between different strand compositions is achieved through component exchange. These features have relevance for nanomechanical devices. We present a morphological and functional analysis of such systems developed in our laboratories.

Controlled Folding, Motional, and Constitutional Dynamic Processes of Polyheterocyclic Molecular Strands

Reversible folding/unfolding of linear molecular strands into helical channel-like complexes upon proton-modulated binding and release of metal ions

Thermodynamics and kinetics of the transition metal complexes of tripodal amines

Substitution reactions of metallic complexes of .beta.,.beta.',.beta.''-triaminotriethylamine. X. Synthesis and characterization of chromium(III) complexes of .beta.,.beta.',.beta.''-triaminotriethylamine and kinetics of primary and secondary aquation of the dichloro(.beta.,.beta.'.beta.''-triaminotriethylamine)chromium(III) cation

Sybil G. Zipp

Papers

Thermodynamics and kinetics of the transition metal complexes of tripodal amines

Six-coordinate halogen complexes of rhodium(III) and iridium(III) with 2,2′,2″-triammoniotriethylamine, N(CH2CH2NH3)3+3 as the cation

Disulfoxide complexes with lanthanum perchlorate

Deuterium isotope effect on the kinetics of aquation of dichloro(β,β′,β″-triaminotriethylamine)cobalt(III) ion