Twisting the Phenyls in Aryl Diphosphenes (Ar-P=P-Ar). Significant Impact upon Lowest Energy States

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Show simple item record Peng, H en Payton, JL en Protasiewicz, JD en Simpson, Miriam en 2012-03-29T00:49:14Z en 2009 en
dc.identifier.citation JOURNAL OF PHYSICAL CHEMISTRY A 113(25):7054-7063 25 Jun 2009 en
dc.identifier.issn 1089-5639 en
dc.identifier.uri en
dc.description.abstract Aryl diphosphenes (Ar-PdP-Ar) possess features that may make them useful in photonic devices, including the possibility for photochemical E-Z isomerization. Development of good models guided by computations is hampered by poor correspondence between predicted and experimental UV/vis absorption spectra. A hypothesis that the phenyl twist angle (i.e., PPCC torsion) accounts for this discrepancy is explored, with positive findings. DFT and TDDFT (B3LYP) were applied to the phenyl-PdP-phenyl (Ph-PdP-Ph) model compound over a range of phenyl twist angles, and to the Ph-PdP-Ph cores of two crystallographically characterized diphosphenes: bis-(2,4,6-tBu3C6H2)-diphosphene (Mes*-PdP-Mes*) and bis-(2,6-Mes2C6H3)- diphosphene (Dmp-PdP-Dmp). A shallow PES is observed for the model diphosphene: the full range of phenyl twist angles is accessible for under 5 kcal/mol. The Kohn-Sham orbitals (KS-MOs) exhibit stabilization and mixing of the two highest energy frontier orbitals: the n+ and π localized primarily on the -PdP- unit. A simple, single-configuration model based upon this symmetry-breaking is shown to be consistent with the major features of the measured UV/vis spectra of several diphosphenes. Detailed evaluation of singlet excitations, transition energies and oscillator strengths with TDDFT showed that the lowest energy transition (S1 r S0) does not always correspond to the LUMO r HOMO configuration. Coupling between the phenyl rings and central -PdP- destabilizes the π-π* dominated state. Hence, the S1 is always n+-π* in nature, even with a π-type HOMO. This coupling of the ring and -PdP- π systems engenders complexity in the UV/vis absorption region, and may be the origin of the variety of photobehaviors observed in diphosphenes. en
dc.publisher American Chemical Society en
dc.relation.ispartofseries Journal of Physical Chemistry A en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. Details obtained from: en
dc.rights.uri en
dc.title Twisting the Phenyls in Aryl Diphosphenes (Ar-P=P-Ar). Significant Impact upon Lowest Energy States en
dc.type Journal Article en
dc.identifier.doi 10.1021/jp810119k en
pubs.begin-page 7054 en
pubs.volume 113 en
dc.rights.holder Copyright: American Chemical Society en
dc.identifier.pmid 19496568 en
pubs.end-page 7063 en
dc.rights.accessrights en
pubs.subtype Article en
pubs.elements-id 94498 en Science en Physics en
pubs.record-created-at-source-date 2010-09-01 en
pubs.dimensions-id 19496568 en

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