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A Novel Redox‐Active Conjugated Palladium Homobimetallic Complex
Author(s) -
Moriuchi Toshiyuki,
Bandoh Seiji,
Miyaishi Manabu,
Hirao Toshikazu
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200103)2001:3<651::aid-ejic651>3.0.co;2-6
Subject(s) - diimine , chemistry , moiety , palladium , conjugated system , quinone , redox , delocalized electron , benzoquinone , ligand (biochemistry) , molecule , stereochemistry , photochemistry , crystallography , organic chemistry , polymer , catalysis , biochemistry , receptor
The π‐conjugated molecule N,N′ ‐bis(4′‐dimethylaminophenyl)‐1,4‐benzoquinone diimine (L 2 ) was incorporated into the palladium(II) complex 1 bearing the N,N′ ‐bis(2‐phenylethyl)‐2,6‐pyridinedicarboxamide ligand, to afford the redox‐active conjugated palladium(II) homobimetallic complex 2 . An X‐ray crystal structure determination of 2 reveals that two palladium complex units are bridged by the quinone diimine moiety to form the C 2 ‐symmetrical 2:1 complex with an anti configuration, and that the bridging π‐conjugated spacer moieties are aligned along a straight line almost parallel to the a axis, to form the columns of the π‐conjugated molecules in the molecular packing. Variable temperature 1 H NMR studies of the conjugated complex 2 indicate that the syn configuration is enthalpically more favorable than the anti configuration in CD 2 Cl 2 by 1.0 kcal/mol, but entropically less favorable by 4.5 cal/mol from the van’t Hoff plot. The redox function of the quinone diimine moiety is modulated by complexation with the palladium complex 1 . The conjugated complex 2 shows three separate redox waves assignable to the successive one‐electron reduction of the quinone diimine moiety and one‐electron oxidation process of the two terminal dimethylamino groups. Chemical reduction of 2 in THF with CoCp 2 resulted in the appearance of ESR signals with weak 105 Pd coupling centered around g = 2.0041. The added electrons are considered to be delocalized over the Pd II ‐quinone diimine d‐π* system in the complex.