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Unexpected Drastic Decrease in the Excited‐State Electronic Communication between Porphyrin Chromophores Covalently Linked by a Palladium(II) Bridge
Author(s) -
Abdelhameed Mohammed,
Karsenti PaulLudovic,
Langlois Adam,
Lefebvre JeanFrançois,
Richeter Sébastien,
Ruppert Romain,
Harvey Pierre D.
Publication year - 2014
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.201403146
Subject(s) - chromophore , porphyrin , photochemistry , density functional theory , acceptor , chemistry , singlet state , excited state , covalent bond , palladium , crystallography , computational chemistry , atomic physics , catalysis , organic chemistry , physics , condensed matter physics
A dyad built up of a zinc(II) porphyrin and the corresponding free base, [Zn‐Fb] , fused to N‐heterocyclic carbene (NHCs) ligands, respectively acting as singlet energy donor and acceptor, and a bridging trans ‐PdI 2 unit, along with the corresponding [Zn‐Zn] and [Fb‐Fb] dimers were prepared and investigated by absorption and emission spectroscopy and density functional computations. Despite favorable structural and spectroscopic parameters, unexpectedly slow singlet energy transfer rates are measured in comparison with the predicted values by the Förster theory and those observed for other structurally related dyads. This observation is rationalized by the lack of large molecular orbital (MO) overlaps between the frontier MOs of the donor and acceptor, thus preventing a double electron exchange through the trans ‐PdI 2 bridge, and by an electronic shielding induced by the presence of this same linker preventing the two chromophores to fully interact via their transition dipoles.