Abstract
A two-electron oxidation of the Cu II (9) and Zn II (12) complexes of tetraphenyltetrabenzoporphyrin (TPTBP) results in the formation of stable antiaromatic [(TPTBP)Cu II(H 2O)] 2+·2 [SbF 6] - (10) and [(TPTBP)Zn II(H 2O) 2] 2+·2 [SbF 6] - (13) with 16π electrons on the inner ligand perimeter. X-ray structures of the parent TPTBP complexes, the dications, and singly oxidized species [(TPTBP)Cu II] ·+[SbF 6] - (11) reveal that the use of TPTBP rather than a porphyrin ligand reduces the degree of nonplanarity in the 16π-electron species relative to the parent 18π complex. Significant high-field shifts of the 1H NMR signals of the outer ring protons and large positive values in calculations of nucleus-independent chemical shifts on the central cavity of the porphyrin ring provide unambiguous evidence for the antiaromatic character of the 16π Zn II species. A combination of magnetic circular dichroism spectroscopic studies and TD-DFT calculations on both the Zn II and Cu II species demonstrates that the main electronic bands of the dicationic species can be readily assigned by using Michl's 4N perimeter model. Femtosecond transient absorption studies clearly demonstrated that the number of π electrons on the inner ligand perimeter and the configuration of the central metal ion play a critical role in the excited-state relaxation dynamics. Redox potentials for conversion between the 16π, 17π, and 18π systems were measured by cyclic voltammetry in dichloromethane and benzonitrile, and UV/Vis spectra of each oxidation/reduction product were monitored by thin-layer spectroelectrochemistry.
| Original language | English |
|---|---|
| Pages (from-to) | 3566-3581 |
| Number of pages | 16 |
| Journal | Chemistry - A European Journal |
| Volume | 18 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - 2012 Mar 19 |
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- Chemistry(all)
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Synthesis, characterization, and spectroscopic analysis of antiaromatic benzofused metalloporphyrins. / Sugawara, Shun; Hirata, Yusuke; Kojima, Satoshi; Yamamoto, Yohsuke; Miyazaki, Eigo; Takimiya, Kazuo; Matsukawa, Shiro; Hashizume, Daisuke; MacK, John; Kobayashi, Nagao; Fu, Zhen; Kadish, Karl M.; Sung, Young Mo; Kim, Kil Suk; Kim, Dongho.
In: Chemistry - A European Journal, Vol. 18, No. 12, 19.03.2012, p. 3566-3581.Research output: Contribution to journal › Article
TY - JOUR
T1 - Synthesis, characterization, and spectroscopic analysis of antiaromatic benzofused metalloporphyrins
AU - Sugawara, Shun
AU - Hirata, Yusuke
AU - Kojima, Satoshi
AU - Yamamoto, Yohsuke
AU - Miyazaki, Eigo
AU - Takimiya, Kazuo
AU - Matsukawa, Shiro
AU - Hashizume, Daisuke
AU - MacK, John
AU - Kobayashi, Nagao
AU - Fu, Zhen
AU - Kadish, Karl M.
AU - Sung, Young Mo
AU - Kim, Kil Suk
AU - Kim, Dongho
PY - 2012/3/19
Y1 - 2012/3/19
N2 - A two-electron oxidation of the Cu II (9) and Zn II (12) complexes of tetraphenyltetrabenzoporphyrin (TPTBP) results in the formation of stable antiaromatic [(TPTBP)Cu II(H 2O)] 2+·2 [SbF 6] - (10) and [(TPTBP)Zn II(H 2O) 2] 2+·2 [SbF 6] - (13) with 16π electrons on the inner ligand perimeter. X-ray structures of the parent TPTBP complexes, the dications, and singly oxidized species [(TPTBP)Cu II] ·+[SbF 6] - (11) reveal that the use of TPTBP rather than a porphyrin ligand reduces the degree of nonplanarity in the 16π-electron species relative to the parent 18π complex. Significant high-field shifts of the 1H NMR signals of the outer ring protons and large positive values in calculations of nucleus-independent chemical shifts on the central cavity of the porphyrin ring provide unambiguous evidence for the antiaromatic character of the 16π Zn II species. A combination of magnetic circular dichroism spectroscopic studies and TD-DFT calculations on both the Zn II and Cu II species demonstrates that the main electronic bands of the dicationic species can be readily assigned by using Michl's 4N perimeter model. Femtosecond transient absorption studies clearly demonstrated that the number of π electrons on the inner ligand perimeter and the configuration of the central metal ion play a critical role in the excited-state relaxation dynamics. Redox potentials for conversion between the 16π, 17π, and 18π systems were measured by cyclic voltammetry in dichloromethane and benzonitrile, and UV/Vis spectra of each oxidation/reduction product were monitored by thin-layer spectroelectrochemistry.
AB - A two-electron oxidation of the Cu II (9) and Zn II (12) complexes of tetraphenyltetrabenzoporphyrin (TPTBP) results in the formation of stable antiaromatic [(TPTBP)Cu II(H 2O)] 2+·2 [SbF 6] - (10) and [(TPTBP)Zn II(H 2O) 2] 2+·2 [SbF 6] - (13) with 16π electrons on the inner ligand perimeter. X-ray structures of the parent TPTBP complexes, the dications, and singly oxidized species [(TPTBP)Cu II] ·+[SbF 6] - (11) reveal that the use of TPTBP rather than a porphyrin ligand reduces the degree of nonplanarity in the 16π-electron species relative to the parent 18π complex. Significant high-field shifts of the 1H NMR signals of the outer ring protons and large positive values in calculations of nucleus-independent chemical shifts on the central cavity of the porphyrin ring provide unambiguous evidence for the antiaromatic character of the 16π Zn II species. A combination of magnetic circular dichroism spectroscopic studies and TD-DFT calculations on both the Zn II and Cu II species demonstrates that the main electronic bands of the dicationic species can be readily assigned by using Michl's 4N perimeter model. Femtosecond transient absorption studies clearly demonstrated that the number of π electrons on the inner ligand perimeter and the configuration of the central metal ion play a critical role in the excited-state relaxation dynamics. Redox potentials for conversion between the 16π, 17π, and 18π systems were measured by cyclic voltammetry in dichloromethane and benzonitrile, and UV/Vis spectra of each oxidation/reduction product were monitored by thin-layer spectroelectrochemistry.
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U2 - 10.1002/chem.201101846
DO - 10.1002/chem.201101846
M3 - Article
VL - 18
SP - 3566
EP - 3581
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
SN - 0947-6539
IS - 12
ER -