Design and Synthesis of a Noninnocent Multitopic Catechol and Pyridine Mixed Ligand: Nanoscale Polymers and Valence Tautomerism

Abstract

The design and synthesis of a new redox-active ligand combining catechol and pyridine units have allowed the achievement of cobalt-based nanoscale coordination polymer particles in a single-step exhibiting a switchable valence tautomeric behavior and thermal hysteresis. The combination of polymerizing capabilities with redox-active responses in a unique ligand leads to the formation of nanoparticles exhibiting a gradual valence tautomeric interconversion in the 35-370 K temperature range. Using one single ligand to obtain these nanoparticles facilitates possible nanostructure formation methodologies.

Valence Tautomerism in One-Dimensional Coordination Polymers

“…40 These compounds also exhibit a strong dependence of the nature of the VT transition on the solvation of the compound, as has been observed previously for non-polymeric VT complexes. [36][37][38]41 Finally, Sato and co-workers have very recently reported a thermally-induced VT transition for 1D cobalt-dioxolene CP with 4,4'-bipyridyl ligands linking cobalt bis-dioxolene units with chiral dioxolene ligands. 42 In search of new CPs that undergo VT transitions, we employed the divergent bis-pyridyl ligands (Chart 1) 1,2-bi(4-pyridyl)ethane (1,2-bpe), trans-4,4'-azopyridine (azpy) and 1,3-bis(4pyridyl)propane (1,3-bpp) to link {Co(3,5dbdiox)2} units.…”

“…37 More recently, the same group reported a new VT CP using a multitopic ligand that combines a catechol and a pyridine unit, although the dimensionality of the CP was not established. 38 Another N-donor linking ligand -meso-alpha,beta-di(4-pyridyl)glycol (dpg)was used by Tao et al to synthesise a "cis" 1D zig-zag chain, which undergoes thermal, pressure and light induced VT intraconversion. 39 The same group reported three 1D VT complexes containing Codioxolene units connected by exo-bidentate pyridine ligands: 1,2-bis(4-pyridyl)ethylene, trans-4,4'azopyridine and 1,4-bis(4-pyridyl)benzene, one of which displays thermal and light-induced VT transitions.…”

Synthesis of a Photo‐Caged DOPA Derivative by Selective Alkylation of 3,4‐Dihydroxybenzaldehyde

“…These animals use different DOPA‐rich proteins to adhere to almost all types of substrate under wet conditions In general, the metal coordination forces provided by the DOPA residue are optimal for this task because their strength is intermediate between those of covalent bonds, which are too strong, and Van der Waals interactions, which are too weak. At the same time, unique features displayed by the catechol function have inspired bench chemists to apply various synthetic approaches to further expand the use of catechol moieties by exploring their antioxidant activity, radical scavenging, and metal chelation …”

Switchable colloids, thin-films and interphases based on metal complexes with non-innocent ligands: the case of valence tautomerism and their applications

“…In a forerunner effort, our group has recently reported the synthesis of a novel bifunctional ligand combining a catechol and a pyridine moiety, so that both electroactive and polymerising capabilities are simultaneously present in a single unit. 22 The reaction of this ligand with a Co(II) salt led to the polymerisation and fast precipitation of amorphous roundshaped nanoparticles of a few hundred nanometres in width ( Fig. 2a).…”