116211-32-6Relevant articles and documents
Imidazole-Bridged Tetrameric Group(IV) Heteroleptic Complexes from the Spontaneous Metal-Ligand Assembly of a Potentially N4-Tetradentate Ligand
Luconi, Lapo,Tuci, Giulia,Yakhvarov, Dmitry,Poli, Giovanni,Rossin, Andrea,Khusnuriyalova, Aliya,Giambastiani, Giuliano
, p. 4384 - 4393 (2019)
The imidazole-containing N4-tetradentate ligand N-(2-(1H-imidazol-2-yl)-3-(pyridin-2-yl)propyl)-2,6-diisopropylaniline (L2H) and its N-benzyl-protected variant (L2Bn) at the imidazole fragment have been synthesized and fully characterized. Both molecules contain an unresolved Csp3 stereogenic center. The coordination behavior of the newly prepared ligands towards group IV metal ions (MIV = Zr, Hf) has been examined through multinuclear 1H and 13C{1H} NMR spectroscopy and selected single-crystal X-ray structural analyses. The ability of the imidazole fragment to enter the metal coordination sphere as a neutral or a monoanionic system has also been investigated, unveiling quite original coordination modes as well as unexpected molecular architectures. When one N imidazole atom is blocked by a benzyl protecting group (L2Bn), the ligand reaction with MIV(NMe2)4 (MIV = Zr, Hf) as metal precursor gives rise to discrete monometallic tris(dimethylamido) 5-coordinated compounds of general formula L2BnM(NMe2)3. The ligand chelates the metal ion as a bidentate monoanionic κ2{N–,N} system through the imidazole moiety and the anilido N donor while an uncoordinated picolyl arm dangles away from the metal center. Upon coordination to the metal ion, the unprotected L2H undergoes a unique self-assembly of the chiral racemic ligand to generate an achiral tetrameric network featuring a regularly alternating (R*,S*,R*,S*) configuration around the 6-coordinated metal centers. The resulting bis(dimethylamido) tetrameric architectures of formula [L2HM(NMe2)2]4 named “poker complexes” contain the imidazole fragment of each ligand bridging two adjacent MIV ions in a μ-κ{N}:κ{N–} coordination hapticity. At the same time, the picolyl fragments of each chelating L2H ligand “sting” a neighboring metal center as unconventional scorpion's tails that impose further rigidity to the tetrameric structure.
A switching cascade of hydrazone-based rotary switches through coordination-coupled proton relays
Ray, Debdas,Foy, Justin T.,Hughes, Russell P.,Aprahamian, Ivan
, p. 757 - 762 (2013/01/14)
Imidazole, a subunit of histidine, plays a crucial role in proton-relay processes that are important for various biological activities, such as metal efflux, viral replication and photosynthesis. We show here how an imidazolyl ring incorporated into a rotary switch based on a hydrazone enables a switching cascade that involves proton relay between two different switches. The switching process starts with a single input, zinc(II), that initiates an E/Z isomerization in the hydrazone system through a coordination-coupled proton transfer. The resulting imidazolium ring is unusually acidic and, through proton relay, activates the E/Z isomerization of a non-coordinating pyridine-containing hydrazone switch. We hypothesize that the reduction in the acid dissociation constant of the imidazolium ring results from a combination of electrostatic and conformational effects, the study of which might help elucidate the proton-coupled electron-transfer mechanism in photosynthetic bacteria.
