Journal article
Experimental and Theoretical Characterization of 5,10‐Diminoporphodimethenes: Dearomatized Porphyrinoids from Palladium‐Catalyzed Hydrazinations of 5,10‐Diarylporphyrins
ChemPlusChem, Vol.79(6), pp.813-824
2014
Abstract
A new dearomatized porphyrinoid, 5,10‐diiminoporphodimethene (5,10‐DIPD), has been prepared by palladium‐catalyzed hydrazination of 5,10‐dibromo‐15,20‐bis(3,5‐di‐tert‐butylphenyl)porphyrin and its nickel(II) complex, by using ethyl and 4‐methoxybenzyl carbazates. The oxidative dearomatization of the porphyrin ring occurs in high yield. Further oxidation with 2,3‐dichloro‐5,6‐dicyanobenzoquinone forms the corresponding 5,10‐bis(azocarboxylates), thereby restoring the porphyrin aromaticity. The UV/visible spectra of the NiII DIPDs exhibit remarkable redshifts of the lowest‐energy bands to 780 nm, and differential pulse voltammetry reveals a contracted electrochemical HOMO–LUMO gap of 1.44 V. Density functional theory (DFT) was used to calculate the optimized geometries and frontier molecular orbitals of model 5,10‐DIPD Ni7c and 5,10‐bis(azocarboxylate) Ni8c. The conformations of the carbamate groups and the configurations of the CNZ unit were considered in conjunction with the NOESY spectra, to generate the global minimum geometry and two other structures with slightly higher energies. In the absence of solution data regarding conformations, ten possible local minimum conformations were considered for Ni8c. Partition of the porphyrin macrocycle into tri‐ and monopyrrole fragments in Ni7c and the inclusion of terminal conjugating functional groups generate unique frontier molecular orbital distributions and a HOMO–LUMO transition with a strong element of charge transfer from the monopyrrole ring. Time‐dependent DFT calculations were performed for the three lowest‐energy structures of Ni7c and Ni8c, and weighting according to their energies allowed the prediction of the electronic spectra. The calculations reproduce the lower‐energy regions of the spectra and the overall forms of the spectra with high accuracy, but agreement is not as good in the Soret region below 450 nm.
Details
- Title
- Experimental and Theoretical Characterization of 5,10‐Diminoporphodimethenes: Dearomatized Porphyrinoids from Palladium‐Catalyzed Hydrazinations of 5,10‐Diarylporphyrins
- Authors
- Bruno Bašić (Author) - Queensland University of TechnologyOliver B Locos (Author) - Queensland University of TechnologyLlew Rintoul (Author) - Queensland University of TechnologyJinglan Kan (Author) - University of Science and Technology BeijingJianzhuang Jiang (Author) - University of Science and Technology BeijingDennis P Arnold (Author) - Queensland University of Technology
- Publication details
- ChemPlusChem, Vol.79(6), pp.813-824; 12
- Publisher
- Wiley-VCH Verlag GmbH & Co. KGaA
- DOI
- 10.1002/cplu.201300433
- ISSN
- 2192-6506
- Organisation Unit
- School of Education and Tertiary Access; University of the Sunshine Coast, Queensland; School of Tertiary Access - Legacy
- Language
- English
- Record Identifier
- 99514907802621
- Output Type
- Journal article
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