Electrochemical synthesis and characterisation of alternating tripyridyl-dipyrrole molecular strands with multiple nitrogen-based donor-acceptor binding sites.
Synthesis of alternating pyridine-pyrrole molecular strands composed of two electron-rich pyrrole units (donors) sandwiched between three pyridinic cores (acceptors) is described. The envisioned strategy was a smooth electrosynthesis process involving ring contraction of corresponding tripyridyl-dipyridazine precursors. 2,6-Bis[6-(pyridazin-3-yl)]pyridine ligands 2a-c bearing pyridine residues at the terminal positions were prepared in suitable quantities by a Negishi metal cross-coupling procedure. The yields of heterocyclic coupling between 2-pyridyl zinc bromide reagents 12a-c and 2,6-bis(6-trifluoromethanesulfonylpyridazin-3-yl)pyridine increased from 68 to 95% following introduction of electron-donating methyl groups on the metallated halogenopyridine units. Favorable conditions for preparative electrochemical reduction of tripyridyl-dipyridazines 2b,c were established in THF/acetate buffer (pH 4.6)/acetonitrile to give the targeted 2,6-bis[5-(pyridin-2-yl)pyrrol-2-yl]pyridines 1b and 1c in good yields. The absorption behavior of the donor-acceptor tripyridyl-dipyrrole ligands was evaluated and compared to theoretical calculations. Highly fluorescent properties of these chromophores were found (ν(em)≈2 × 10(4) cm(-1) in MeOH and CH(2)Cl(2)), and both pyrrolic ligands exhibit a remarkable quantum yield in CH(2)Cl(2) (φ(f)=0.10). Structural studies in the solid state established the preferred cis conformation of the dipyrrolic ligands, which adopting a planar arrangement with an embedded molecule of water having a complexation energy exceeding 10 kcal mol(-1). The ability of the tripyridyl-dipyrrole to complex two copper(II) ions in a pentacoordinate square was investigated.
Tabatchnik-Rebillon
Alexandra
A
Laboratoire de Chimie et Interdisciplinarité: Synthèse, Analyse, Modélisation (CEISAM), UMR 6230, Université de Nantes, UFR des Sciences et des Techniques, 2, rue de la Houssinière, BP 92208, 44322 Nantes Cedex 3, France.
Aubé
Christophe
C
Bakkali
Hicham
H
Delaunay
Thierry
T
Manh
Gabriel Thia
GT
Blot
Virginie
V
Thobie-Gautier
Christine
C
Renault
Eric
E
Soulard
Marine
M
Planchat
Aurélien
A
Le Questel
Jean-Yves
JY
Le Guével
Rémy
R
Guguen-Guillouzo
Christiane
C
Kauffmann
Brice
B
Ferrand
Yann
Y
Huc
Ivan
I
Urgin
Karène
K
Condon
Sylvie
S
Léonel
Eric
E
Evain
Michel
M
Lebreton
Jacques
J
Jacquemin
Denis
D
Pipelier
Muriel
M
Dubreuil
Didier
D
D000970:Antineoplastic Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001665:Binding Sites; D002384:Catalysis; D049109:Cell Proliferation / Q000187:drug effects; D003300:Copper / Q000737:chemistry*; D004354:Drug Screening Assays, Antitumor; D055664:Electrochemical Techniques; D005260:Female; D006801:Humans; D008024:Ligands; D008297:Male; D008956:Models, Chemical; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D011758:Pyrroles / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology
D000970:Antineoplastic Agents; D008024:Ligands; D011725:Pyridines; D011758:Pyrroles; D003300:Copper; D009584:Nitrogen