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Molecular Switches for any pH: A Systematic Study of the Versatile Coordination Behaviour of Cyclam Scorpionands
Author(s) -
Lau Yu Heng,
Clegg Jack K.,
Price Jason R.,
Macquart Rene B.,
Todd Matthew H.,
Rutledge Peter J.
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201703488
Subject(s) - cyclam , chemistry , ligand (biochemistry) , metal , coordination complex , titration , side chain , reactivity (psychology) , combinatorial chemistry , nickel , molecular recognition , transition metal , molecule , crystallography , nanotechnology , materials science , inorganic chemistry , organic chemistry , catalysis , polymer , medicine , biochemistry , receptor , alternative medicine , pathology
Molecular switches have many potential applications in nanoscience and biomedicine. Transition metal complexes that can be switched from an inert, unreactive state to a catalytically active one by a simple change in conditions (e.g. pH shift) or by binding to a specific biomolecular target—so‐called target‐activated metal complexes (TAMCs)—hold particular allure as a means of harnessing the potent but at times indiscriminate reactivity of metal‐based drugs. Towards this goal, we have prepared a series of ten structurally related ligands, each of which bears a different pendant side‐arm functional group appended to a common macrocyclic core, along with copper(II) and nickel(II) complexes of these cyclam‐based “molecular scorpionands”. X‐ray crystal structures reveal a variety of binding modes between pendant side‐arm and metal centre that depend on the constituent donor atoms. To investigate the switchability of side‐arm coordination in solution, spectrophotometric pH titrations were carried out for all 20 metal complexes. The majority of the complexes undergo spectroscopic changes that are consistent with a switch in pendant coordination state at a specific pH. This ligand series represents a comprehensive model platform from which to build pH‐switchable metal complexes for applications in nanoscience and biomedicine.