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Electrochemical Synthesis and Characterisation of Alternating Tripyridyl–Dipyrrole Molecular Strands with Multiple Nitrogen‐Based Donor–Acceptor Binding Sites
Author(s) -
TabatchnikRebillon Alexandra,
Aubé Christophe,
Bakkali Hicham,
Delaunay Thierry,
Manh Gabriel Thia,
Blot Virginie,
ThobieGautier Christine,
Renault Eric,
Soulard Marine,
Planchat Aurélien,
Le Questel JeanYves,
Le Guével Rémy,
GuguenGuillouzo Christiane,
Kauffmann Brice,
Ferrand Yann,
Huc Ivan,
Urgin Karène,
Condon Sylvie,
Léonel Eric,
Evain Michel,
Lebreton Jacques,
Jacquemin Denis,
Pipelier Muriel,
Dubreuil Didier
Publication year - 2010
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.201000859
Subject(s) - electrosynthesis , chemistry , pyridine , negishi coupling , pyrrole , electrochemistry , acceptor , reagent , electron acceptor , chromophore , molecule , photochemistry , stereochemistry , medicinal chemistry , organic chemistry , physics , electrode , condensed matter physics
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 2 a – 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 12 a – 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 2 b , 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 1 b and 1 c 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.